Best Practices for Designing Modular Skylight Systems with Suspended Ceilings

Transcription

1 Best Practices for Designing Modular Skylight Systems with Suspended Ceilings By Puja Manglani, Rocelyn Dee Jon McHugh, Lisa Heschong, Heschong Mahone Group August 2003 California Energy Commission Public Interest Energy Research (PIER) Program

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5 CALIFORNIA COMMISSION ENERGY Best Practices for Designing Modular Skylight Systems for Suspended Ceilings Design Guidelines AUGUST D5.4.4 Gray Davis, Governor

6 ii PIER Integrated Ceilings Project

7 CALIFORNIA ENERGY COMMISSION Prepared By: Heschong Mahone Group Jon McHugh, Lead Author Fair Oaks, CA Managed By: New Buildings Institute Cathy Higgins, Program Director White Salmon, WA CEC Contract No Prepared For: Donald Aumann, Contract Manager Nancy Jenkins, PIER Buildings Program Manager Terry Surles, PIER Program Director Robert L. Therkelsen Executive Director DISCLAIMER This report was prepared as the result of work sponsored by the California Energy Commission. It does not necessarily represent the views of the Energy Commission, its employees or the State of California. The Energy Commission, the State of California, its employees, contractors and subcontractors make no warrant, express or implied, and assume no legal liability for the information in this report; nor does any party represent that the uses of this information will not infringe upon privately owned rights. This report has not been approved or disapproved by the California Energy Commission nor has the California Energy Commission passed upon the accuracy or adequacy of the information in this report.

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9 TABLE OF CONTENTS TABLE OF CONTENTS V LIST OF FIGURES VIII PREFACE X Legal Notice x OVERVIEW 1 A CASE FOR SKYLIGHTS AND SUSPENDED CEILINGS 1 Why Use Skylights? 1 Better Light Quality 1 Energy Savings 2 Productivity Increase 2 Sales Increase 2 Why Use Suspended Ceilings? 3 Flexibility 3 Acoustic Absorption 3 Concealing Plenum Spaces 3 Market Potential 4 Skylight Market 4 Suspended Ceiling Market 5 Product Delivery Options 6 Current Building Practice 7 Current Applications 8 Obstacles to Mass Application 8 Need for Modular Light wells 9 Future Skylighting Trends in California 10 Organization of Guidelines 10 NOMENCLATURE AND FUNCTIONS Skylight Throat Splay Light Control Devices Suspended Ceiling Other Accessories 16 SYSTEM DESIGN 17 Systems Coordination 17 Coordination Strategies During the Design Phase 18 PIER Integrated Ceiling Systems v

10 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS TABLE OF CONTENTS Coordination Strategies During the Construction Phase 19 Design Process for Skylight Wells 20 Schematic Design Phase 21 Design Development Phase 21 Skylight Well Sizing and Geometry 22 Photometric Analysis 28 COMPONENT REQUIREMENTS 33 Skylight 33 Minimum Performance Requirements 33 Design Options 34 Throat 36 Minimum Performance Requirements 36 Design Options 37 Splay 39 Minimum Performance Requirements 39 Design Options 41 Light Control Devices 41 Minimum Performance Requirements 41 Design Options 42 Suspended Ceiling System 43 Minimum Performance Requirements 44 Other Accessories 44 Minimum Performance Requirements 44 PRODUCT EVALUATION AND APPROVAL 47 Code Bodies 47 Product Evaluation 47 Code Requirements 48 Fire Ratings 48 Insulation Location 49 Seismic Rating 49 Applicable Tests 50 Future Evaluation Standards 50 Seismic 50 Fire Safety 51 CONCEPTUAL SYSTEMS 53 Systems Descriptions 53 System 1: Flexible Threaded Rod (Fixed Splay) System 53 System 2: Fixed Metal Throat (Adjustable Splay) System 55 System 3: Tubular Adjustable Throat (Fixed Splay) System 56 System 4: Fixed Throat Flexible Connector (Fixed Splay) System 57 Sample Project 58 Schematic Design 58 Design Development 68 Component Specifications 72 vi PIER Integrated Ceilings Project

11 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS TABLE OF CONTENTS REFERENCES 75 GLOSSARY 77 APPENDIX 79 Appendix 1: Acronyms 79 Appendix 2: National Construction Volume 80 Appendix 3: Market Potential for Suspended Ceiling Systems in Splay Applications 81 Assumptions 81 Calculations 81 Summary 81 Appendix 4: Skylight Sizing Chart 82 Appendix 5: Code Requirements 83 Plastic Skylights 83 Glass Skylights 83 Appendix 6: Applicable Tests 84 Plastic Skylights 84 Glass Skylights 84 Skylights with Plastic Frames 85 Miscellaneous Tests 85 Appendix 7: Well Assembly Schedule 87 Condition A: Owner-Occupied New Construction Option 1 87 Condition B: Owner-Occupied New Construction Option 2 87 Condition C: Tenant-Occupied Construction as Tenant Improvements 88 Condition D: Remodel of Existing Building 88 PIER Integrated Ceiling Systems vii

12 LIST OF FIGURES Figure 1. Skylight application in an office: SMUD Office in Sacramento. 1 Figure 2. Ralph's Grocery. 2 Figure 3. Energy savings of Ralph s Grocery. 2 Figure 4. Suspended ceiling in an office. 3 Figure 5. California new and retrofit construction expressed as percentage floor area by occupancy. 4 Figure 6. New construction floor area under roof in the United States (annual average from 1990 to 1999). 5 Figure 7. Advantages and disadvantages of product delivery options. 7 Figure 8. Column going through light well splay. 8 Figure 9. Ill-fitting acoustic panels in light well splay. 9 Figure 10. Section of skylight well (refer to text for definitions. 13 Figure 11. Typical spacing of systems installed within the plenum. 17 Figure 12. Typical spacing of systems installed on the ceiling. 18 Figure 13. Exclusion zone marking in plans 19 Figure 14. Flowchart showing design process of skylight wells 20 Figure 15. Plan showing primary and secondary structural members 23 Figure 16. Skylight spacing with splay. 24 Figure 17. Skylight spacing without splay. 24 Figure 18. Comparison of small vs. large skylights 25 Figure 19. Many small skylights versus fewer large skylights 25 Figure 20. Comparison of skylight wells with and without splay. 26 Figure 21. Skylight without splay results in darker surfaces. 26 Figure 22. Skylight with splay has better light distribution with well-lit walls. 26 Figure 23. Splay angle. 27 Figure 24. Isolux contour. 28 Figure 25. Detailed skylight visualization using Radiance simulation software. 28 Figure 26. Using photometrics to evaluate appropriate luminance levels. 29 Figure 27. Photometric analysis of uniformity due to skylights and electric lights. 30 Figure 28. Details of a skylight. 33 Figure 29. Light distribution of a clear skylight. 34 Figure 30. Light distribution of a diffused skylight. 34 Figure 31. Glass skylight. 35 Figure 32. Different skylight shapes for plastic glazing. 35 PIER Integrated Ceiling Systems viii

13 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS LIST OF FIGURES Figure 33. Cut section of throat. 36 Figure 34. Lightwell made of sheet metal. 37 Figure 35. Tubular light well. 38 Figure 36. Lightwell made of acoustic tiles 38 Figure 37. Gypsum board lightwell 38 Figure 38. Cut section of splay. 39 Figure 39. Acoustic tile splay in a classroom 41 Figure 40. Gypsum board splay 41 Figure 41. Diffusers in commercial areas 42 Figure 42. Reflectors. 42 Figure 43. Louvers in an office space. 43 Figure 44. Baffles in skylights in a classroom. 43 Figure 45. Open loop control scheme. 45 Figure 46. Closed loop control scheme. 46 Figure 47. Stepped switching diagram. 46 Figure 48. Continuous dimming diagram. 46 Figure 49. Conceptual diagram of Flexible Threaded Rod (Fixed Splay) System 53 Figure 50. Conceptual diagram of Fixed Metal Throat (Adjustable Splay) System 55 Figure 51. Conceptual diagram of Tubular Adjustable Throat (Fixed Splay) System 56 Figure 52. Conceptual diagram of Fixed Throat Flexible Connector (Fixed Splay) System_ 57 Figure 53. Skylight well dimensions 59 Figure 54. Data inputs in SkyCalc to calculate the SFR 60 Figure 55. Well efficiency graph 61 Figure 56. Total well efficiency of light well with splay (WE1 x WE2 x Tvis of diffuser) 61 Figure 57. Well efficiency of throat using SkyCalc 62 Figure 58. Well efficiency of splay using SkyCalc 64 Figure 59. Total annual energy savings from skylights (kwh/yr) 65 Figure 60. Total energy cost savings from skylights ($/yr) 65 Figure 61. Well efficiency of light well without splay using SkyCalc 66 Figure 62. Total annual energy savings from skylights-light well without splay (kwh/yr) _ 66 Figure 63. Total energy cost savings from skylights-light well without splay ($/yr) 67 Figure 64. Spacing layout of light well with splay. 67 Figure 65. Layout without splay, 12 skylights (3 x 4 ) with SFR 3.3% 68 Figure 66. Photometric results for light well with splay (clear and cloudy conditions) 70 Figure 67. Photometric results for light well without splay (clear and cloudy conditions) 70 Figure 68. Light well without splay in an open room in cloudy conditions 71 Figure 69. Light well without splay with shelves at near peak daylight levels 71 Figure 70. Skylight well with splay at near peak levels 71 Figure 71. Light well with splay with shelves under peak conditions 71 Figure 72. Light well with splay with shelves and indirect lighting (night time) 72 Figure 73. Light well with splay with direct lighting and photocontrols (night time) 72 PIER Integrated Ceiling Systems ix

14 PREFACE The California Energy Commission s (CEC) Public Interest Energy Research (PIER) program supports research that will bring affordable and energy-efficient products to the marketplace. In fulfillment of this PIER objective, the following design guideline aims to energize the market for modular skylight well systems. It provides guidelines for manufacturers, designers, and contractors in the development and design of skylight well products for suspended ceilings. These guidelines describe a step by step process in designing modular skylight wells, along with a glossary of technical lighting terms and list of acronyms (listed in Appendix 1). The main building types that will benefit from this are new and retrofit constructions of lowrise offices, retail stores and schools installed with suspended ceiling systems. These building types will have the following characteristics: Flat or low-slope roofs, with built-up or membrane roofing Non-fire rated assemblies Unit skylights, with maximum dimensions of 8 or less This design guideline is produced as a public non-proprietary product and is not targeted to a specific construction method or a particular manufacturer. It only discusses requirements of components and connections related to the skylight system and not of adjacent systems, such as the roof assembly or suspended ceilings. The Integrated Energy Systems- Productivity and Buildings Science program is funded by the California Energy Commission under Public Interest Energy Research (PIER) contract No The PIER program is funded by California ratepayers through California's System Benefit Charges and is administered by the California Energy Commission (CEC). Donald J. Aumann is the CEC Programmatic Contact. LEGAL NOTICE THIS REPORT WAS PREPARED AS A RESULT OF WORK SPONSORED BY THE CALIFORNIA ENERGY COMMISSION (COMMISSION). IT DOES NOT NECESSARILY REPRESENT THE VIEWS OF THE COMMISSION, ITS EMPLOYEES, OR THE STATE OF CALIFORNIA. THE COMMISSION, THE STATE OF CALIFORNIA, ITS EMPLOYEES, CONTRACTORS, AND SUBCONTRACTORS MAKE NO WARRANTY, EXPRESS OR IMPLIED, AND ASSUME NO LEGAL LIABILITY FOR THE INFORMATION IN THIS REPORT; NOR DOES ANY PARTY REPRESENT THAT THE USE OF THIS INFORMATION WILL NOT INFRINGE UPON PRIVATELY OWNED RIGHTS. THIS REPORT HAS NOT BEEN APPROVED OR DISAPPROVED BY THE COMMISSION NOR HAS THE COMMISSION PASSED UPON THE ACCURACY OR ADEQUACY OF THE INFORMATION IN THIS REPORT.

15 Best Practices for Designing Modular Skylight Systems for Suspended Ceilings aims to address two types of audiences: designers / project managers, and manufacturers. This document aims to provide designers, project managers, with guidelines for incorporating skylights with light wells in commercial buildings. It discusses the design process, implications of different design solutions, and codes and performance-related issues. It also aims to jump start the modular skylight systems industry by providing product manufacturers with market information, product components requirements, and codes and performance metrics for product evaluation. The solutions presented here are based on research results, as well as inputs from industry members. They are also based on the experiences of project managers and designers who had installed or designed light wells with suspended ceilings. Following the recommendations of this design guideline will result in the effective installation of skylight systems that provide optimal energy performance, and superior lighting quality. OVERVIEW PIER Integrated Ceiling Systems 1

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17 A CASE FOR SKYLIGHTS AND SUSPENDED CEILINGS WHY USE SKYLIGHTS? No space, architecturally, is a space unless it has natural light. Numerous studies have shown the visual benefits of skylights and daylighting, such as aesthetics and better light quality. Apart from these, skylights provide other functional benefits. In commercial building applications, skylights and daylighting result in energy savings, productivity growth, sales increases, and performance improvements. Skylighting is successfully being applied to a wide range of everyday buildings, such as schools, offices, and retail stores. - Louis Kahn, architect Better Light Quality The most apparent benefit of a skylight is its ability to introduce daylight into the interior space. Daylight provides light that is without flicker and has high color rendering qualities essential for commercial building occupancies. Besides adding variability to indoor spaces, skylights provide uniform wide spread illumination In retail applications, good color rendering is important for accurate product representations, especially important for those retail sectors that require customers to make color choices, of items such as paints or cosmetics. Better color choices result in higher customer satisfaction. In office environments, a properly designed daylit space provides better lighting conditions under which to work. This can result in fewer task-related errors. Skylights provide high quality, dependable illumination for office spaces. In schools, they provide a stimulating environment for learning. Figure 1. Skylight application in an office: SMUD Office in Sacramento. PIER Integrated Ceiling Systems 1

18 A Case for Skylights and Suspended Ceilings Modular Skylight Systems with Suspended Ceilings Energy Savings Skylights can result in energy savings due to daylight makes electric lighting unnecessary. Achieving the full energy savings requires the use of daylighting controls, such as photosensors to automatically turn down lights when daylight is available, in conjunction with the skylight installations. In a retail case study funded by the Pacific Gas & Electric Company (PG&E) of Ralph s Grocery in Valencia, CA (see Figure 2), the installation of skylights and daylighting controls resulted in a 30% decrease in lighting energy demand (see Figure 3). 2 This figure illustrates the light energy profile during most of the hours of the day and shows that two-thirds of the light can be shut off due to daylight Productivity Increase The daylight provided by skylight applications has also been credited with higher test scores in schools. A study Figure 2. Ralph's Grocery 1. funded by PG&E surveyed the performance of three school districts in California. It showed that improvements in student performance on test scores as high as 25% is strongly correlated to the presence of daylight in the classrooms. 3 Sales Increase In big-box retail stores, skylights are associated with increased sales. A Wal- Mart store in Lawrence, Kansas was outfitted with skylights in one-half of the store. Information derived from monitoring the sales registers showed that products located under the skylit areas had significantly higher sales than the products sold in the non-daylit areas of the store, 4 Figure 3. Energy savings of Ralph s Grocery 1. Meanwhile, PG&E also funded a survey of 108 retail stores. Two-thirds of them were daylit with skylights while the other third were not. The study showed that the daylit stores had 40% higher sales than the others. 5 This Skylighting and Retail Sales study completed in 1999 by the Heschong Mahone Group found a compelling statistical correlation between the presence of daylighting in a chain retail store and higher sales for those stores. This study found that for a certain retail chain, all other things being equal, stores with skylights experienced 40% higher sales than those without skylights. 2 PIER Integrated Ceiling Systems

19 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS A CASE FOR SKYLIGHTS AND SUSPENDED CEILINGS WHY USE SUSPENDED CEILINGS? Suspended ceilings are desirable because of their aesthetics, inherent flexibility, access to equipment, and acoustic properties. Office and retail spaces require flexibility due to regular tenant changeovers. Offices and schools require acoustic control for a good work environment. In the majority of these projects, the most effective solution is a suspended ceiling system. Flexibility Office and retail spaces experience regular tenant turnovers and often require changes in space layout. Ceiling solutions, such as gypsum board construction on studs, require extensive work and material replacements to accommodate the constant change in space requirements, lighting layouts and air duct relocations. The modular nature of a suspended ceiling system allows for changes without needing expensive new materials or installation labor. Acoustic Absorption Suspended ceilings allow the use of acoustic tiles, which have excellent absorption of sound waves and reduce noise problems. Acoustic qualities of ceilings are especially important in school and work environments. Recognizing that good acoustics is indispensable for verbal learning, a new ANSI (American National Standards Institute) standard for classrooms was issued that has strict acoustic specifications for educational spaces. 6 This standard places reverberation limits on rooms high enough that they essentially require sound-absorbing surfaces in classrooms. In office environments, acoustics also affect the workspace. Noise in the environment affects worker concentration and comfort. A survey of 400 building managers estimated that improvements in acoustics would increase productivity by 26%. 7 Concealing Plenum Spaces In offices, high-end retail stores and classrooms, aesthetics is an important design issue. An exposed ceiling solution requires coordinated design of the mechanical ducts and other systems to produce an organized-looking ceiling design. A suspended ceiling system allows the designer to conceal the plenum without resorting to a more extensive design process and additional finishing costs. In a suburban office case study, 8 an exposed ceiling design would have cost the project $ $0.60 per square foot more than a suspended ceiling installation because of the additional Figure 4. Suspended ceiling in an office. (Source: PIER Integrated Ceiling Systems 3

20 A Case for Skylights and Suspended Ceilings Modular Skylight Systems with Suspended Ceilings duct design work and the finish material. Thus, removing suspended ceilings is not always a cost-saving measure and it sacrifices the flexibility, aesthetics and acoustical benefits associated with it. MARKET POTENTIAL Because of the many benefits of skylights and suspended ceilings, the building market shows that there is a substantial volume of potential clients for these products in commercial buildings. Current design and construction practices indicate that there is a demand for modular skylight well products (See section on Current Building Practice ). In the analysis below, we attempt to quantify the probable market demand within these building types. This information is especially valuable for manufacturers interested in expanding their market share in the building industry. Skylight Market Restaurant 3% Other 16% Hotel 5% Lg Office 20% Sm office 6% Warehouse 18% Medical 4% Education 8% Grocery 4% Retail 16% Figure 5. California new and retrofit construction expressed as percentage floor area by occupancy9. The potential market for modular skylight well products includes the building types that can take advantage of daylight benefits and that require the use of suspended ceiling systems. These are low-rise commercial buildings, such as offices, retail spaces, grocery stores, and schools. Data from the Dodge New Construction database shows that they make up 45% of all new and retrofit construction in California (see Figure 5). With an estimated annual commercial construction volume of 84.8 million sf in California, 10 this means a potential market of the target building types of 38.2 million sf a year. The national construction volume is estimated at 1,109 million sf annually. Educational, retail and office spaces make up million sf or 46% of the total construction volume. 11 This percentage figure is comparable to the California s construction market. 4 PIER Integrated Ceiling Systems

21 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS A CASE FOR SKYLIGHTS AND SUSPENDED CEILINGS Floors Million sq. ft. Fraction of Area Under Fraction Under Total Roof Roof % % % % % 32 3% 4 to % 22 2% > % 3 0% Total 1, % % Figure 6. New construction floor area under roof in the United States (annual average from 1990 to 1999) 12. The market size for skylights can then be determined by the amount of floor area that can be installed with skylights, that is, area that is directly under a roof. In data gathered from the Commercial Building Energy Consumption Survey (CBECS), 68% of all built floor space is directly below a roof. This means that 68% of built floor area can be installed with skylights. With a new construction of office, retail and educational space of million sq. ft. a year, there is a potential market for skylight installations of million sf of floor area annually. Suspended Ceiling Market The suspended ceiling system is widely used in the commercial building sector. According to a study conducted by Armstrong Industries in 2002, suspended ceiling systems are installed in: 68% of all educational facility floor space 45% of all office floor space 46% of all store floor space There is an evident dominance of the suspended ceilings application in these building types. There is a growing use of skylights in combination with suspended ceilings as evidenced by a study of twenty low-rise commercial buildings, 13. There is also potential for this product application (suspended ceiling tiles) to extend to use in the modular skylight well construction, for example as a material for skylight splay construction, as discussed in the later sections of this guideline. Even though skylight installation within a building using a suspended ceiling may result in the loss of the total suspended ceiling installation area, if the skylight well splay is made of acoustic tiles, ceiling manufacturers stand to gain sales volume. To illustrate, take a sample building with suspended ceilings, 4 by 4 skylights and 45 -sloped, 3 high splays. 4% of the roof area will be covered with skylights (approximate skylight-to-floor ratio required to achieve appropriate interior light levels). Because of the skylight installations, 36% of the horizontal ceiling area is displaced due to the splay openings. But if the splay is made out of acoustic tiles, there is an increase of 45% in acoustic tile area. The net gain in product demand will be 9%, as PIER Integrated Ceiling Systems 5

22 A Case for Skylights and Suspended Ceilings Modular Skylight Systems with Suspended Ceilings compared to a building without skylights. (See Appendix 3 for detailed calculations.) Product Delivery Options Manufacturers interested in entering the market for modular skylight wells have different options for product delivery: by fabricating only one or two components of the system and integrating with other manufacturers providing other components, or by providing the whole modular well system as a kit. Each option has advantages and disadvantages, for both the manufacturer and the consumer. 6 PIER Integrated Ceiling Systems

23 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS A CASE FOR SKYLIGHTS AND SUSPENDED CEILINGS Multiple Manufacturers Single Manufacturer Description Different manufacturers will supply the unit skylights, and lightwell components One single manufacturer will supply all components associated with a skylight well system as a kit Advantages Manufacturers can use existing manufacturing expertise and equipment, without having to expand their manufacturing capabilities. Consumers can have multiple sources of interchangeable parts. Consumers can have choice of different solutions. Promotes competition among component suppliers. Single point of responsibility and liability. Less coordination required between different manufacturers. Connections between components can be better designed or even be completely eliminated. Allows manufacturers to differentiate products. An integrated system supplied by a single manufacturer will be more cost-effective. Disadvantages No single point of responsibility and liability for consumers. Requires industry standards for connectors to allow components from different manufacturers to fit together seamlessly. Requires more coordination work during construction. Greater uncertainty in the assembled product s overall performance. Requires expansion of manufacturing capabilities of suppliers beyond their current expertise. Consumers must buy proprietary systems from a single supplier. Figure 7. Advantages and disadvantages of product delivery options. CURRENT BUILDING PRACTICE Information on current building practice and needs are gathered from case studies on existing buildings with integrated skylight wells and from a series of Technical Advisory Group (TAG) meetings conducted with various industry representatives. The case studies consisted of twenty existing projects that have integrated skylight installations with a suspended ceiling system 14. Evaluations were PIER Integrated Ceiling Systems 7

24 A Case for Skylights and Suspended Ceilings Modular Skylight Systems with Suspended Ceilings based on plan reviews, site visits, and interviews with project managers and construction managers. The TAG meetings are brainstorming sessions conducted by the research group to receive inputs from the industry regarding their needs from a modular skylight well market. Participants are architects, lighting designers, and manufacturers of skylights and suspended ceiling systems. These interactions with industry representatives indicate that there is a demand in the building industry for a modular skylight well product. Current Applications Application of skylight wells with suspended ceilings were found to be in both new and retrofit construction work. These projects include classrooms, chain grocery stores, big-box retailers and offices. The existing systems were mostly custom-designed and site-built systems. The only pre-manufactured systems used were tubular skylights. Obstacles to Mass Application Depending on their success in integrating skylights and suspended ceilings, project and construction managers of the case studies gave their feedback on the design and construction process. The major obstacle to the mass application of skylight wells is that due to lack of prefabricated components, these systems have to be custom-designed and site-built. Problems associated with this include cost, difficulty of quality control, performance uncertainty, and difficulty in maintenance. Quality Control Figure 8. Column going through light well splay. Site-built systems require on-site construction of components. The use of manual workmanship can result in inconsistency of quality, which may affect the aesthetics of the space, or in the worst case, safety of occupants. In the case of a grocery store chain, a suspended ceiling system was used for the skylight splay construction. Due to lack of prefabricated splay components, tiles and runners had to be cut and bent on-site. Though the general aesthetics of the sales area was unaffected, a closer inspection would reveal incongruent sizes and shapes of components. Figure 8 and Figure 9 show examples of these issues. Performance Uncertainty The electric lighting industry is mature, with fixtures and luminaries massproduced in factories and every photometric reports provided with light output test results. This information allows designers to predict luminaire performance and to design space lighting accordingly. 8 PIER Integrated Ceiling Systems

25 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS A CASE FOR SKYLIGHTS AND SUSPENDED CEILINGS Meanwhile, outputs of skylight well systems are predicted based on relatively crude calculations by the designer. Their performances are unpredictable and do not conform to any performance standards. The TAG participants have stressed [a need for such a standard. The existence of prefabricated systems will allow tests to be conducted on prototype systems and will allow the final mass-produced product to perform at levels close to the tested results. Maintenance Problems Another type of frequently reported problems are maintenance problems resulting from the use of custom parts. Any replacements that are required would have to be special ordered or have to be re-cut or re-bent, causing inconvenience and delays in the construction schedule. Figure 9. Ill-fitting acoustic panels in light well splay. Higher Cost Some construction managers interviewed would like to see approximately 50% reduction in cost and the availability of a kit of parts skylight system that will make it easier to install. One of the retail case studies 15 evaluated different methods of incorporating a skylight with suspended ceilings, and found the available options quite expensive. While material costs of site-built lightwells may be less than a pre-manufactured skylight well system, their installation costs could be higher. There is a trade-off between material costs, installation costs and number of skylights required. In a custom-designed system, there will be a longer design schedule due to increased coordination work among system designers. In a site-built system, there will be a longer construction schedule due to on-site cutting and adjustments. Need for Modular Light wells The case studies show that there is a demand in the building industry that needs to be addressed. The problems associated with the current method of custom designing and building skylights can be resolved through the use of prefabricated skylight wells. Among the retailers interviewed, 16 one is currently considering using skylights, but is uncertain about how to specify light wells that are compatible with suspended ceilings. Two other retail stores do not use skylights if their stores have dropped ceilings. A major bigbox retailer is currently integrating skylights with suspended ceilings, but has not been doing it on a wider-scale because of lack of a solution better coordinated with other building systems like HVAC, sprinkler, etc. These issues present a challenge for product manufacturers to develop an a more flexible well system that will achieve the required performance criteria while accommodating these inconveniences and improving the coordination process. PIER Integrated Ceiling Systems 9

26 A Case for Skylights and Suspended Ceilings Modular Skylight Systems with Suspended Ceilings FUTURE SKYLIGHTING TRENDS IN CALIFORNIA The market for skylights will be greatly affected by revisions that have been proposed for the 2005 California Energy Code (Title 24). The most notable change that will impact the industry is the establishment of skylights as a prescriptive measure 17 for low-rise nonresidential buildings that have spaces larger than 25,000 sf directly under a roof and with a ceiling height greater than For these buildings, at least half of the space is required to be daylit with skylights or to install an energy efficiency measure that saves as much energy. The code also places a prescriptive upper limit on SFR of 5% for all buildings, except atriums greater than 55 feet high. Since the requirement for skylights is in spaces with ceiling heights greater than 15 feet, only a few buildings with suspended ceilings will be directly affect by the code requirements. However, these code requirements for tall spaces may change the expectations of building owners for low-rise buildings. The standards will also mandate automatic light controls for skylit spaces greater than 2,500 sf. These controls must have multiple steps that are capable of continuous dimming. 19 ORGANIZATION OF GUIDELINES The modular skylight guidelines are organized as follows: Nomenclature and Functions The second chapter establishes a common nomenclature so that industry members can communicate ideas and create understanding. Functions associated with each component are also included to define the basic functional requirements. System Design The third chapter deals with the process of designing a skylight well. Preliminary design is done by using rules of thumb and by accommodating other building services. More in-depth analysis can be accomplished by using photometrics and isolux graphs. This section also discusses the coordination of skylights with other systems from the design to the construction stages of a project. Component Requirements The fourth chapter discusses the geometric and physical properties required of each component to satisfy their performance goals. Product Evaluation and Approval The fifth chapter explains the approvals and evaluation process that will allow modular skylight well systems to be installed in buildings. It addresses the building permit plan check, third-party product evaluation and applicable codes and tests. Conceptual Systems Lastly, the sixth chapter presents four conceptual systems that were developed through brainstorming and design sessions with industry 10 PIER Integrated Ceiling Systems

27 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS A CASE FOR SKYLIGHTS AND SUSPENDED CEILINGS professionals. A detailed step-by-step design process is explained by using one sample system under the Sample Project section. PIER Integrated Ceiling Systems 11

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29 NOMENCLATURE AND FUNCTIONS The skylight well system refers to the set of components necessary to deliver daylight from the exterior, through the plenum space, into the building interior. It encompasses the following components: Figure 10. Section of skylight well (refer to text for definitions. 1. Skylight A skylight is a glazed opening in a roof to admit light. It encompasses the following sub-components: 1a. Frame The skylight frame is the structural frame supporting the glazing of the skylight. It includes the condensation gutters and the seals and gaskets necessary for its installation. PIER Integrated Ceiling Systems 13

30 Nomenclature and Functions Modular Skylight Systems with Suspended Ceilings 1b. Glazing The glazing refers to the glass or plastic lenses used to cover the skylight opening. 1c. Skylight-Curb Connection The skylight-curb connection is the interface between the skylight frame and the rooftop curb. It includes all accessories required for the proper attachment of the skylight, such as fasteners and flashing. 2. Throat The light well is composed of two components, the throat and the splay. They both serve as conveyances of daylight from the skylight to the interior space. The throat is the tubular component (can be rectangular or circular in section) connecting the skylight to the splay. In the absence of a splay, it is attached directly to the ceiling plane. It is comprised of the following components: 2a. Throat Attachment to Structure This connection refers to the interface between the throat and the building structure. This attachment holds up the throat by providing support. 2b. Throat Interconnector This refers to a component that attaches two pieces of throat material (e.g. gypsum board, acoustic tile, or sheet metal tubes) together. It may be a rigid connection, or an adjustable component that allows for vertical, horizontal, or angular displacement of the throat. 2c. Throat Structural Support This refers to the throat support that provides lateral and seismic stability. It may be a rigid brace, hanger wire, or other type of support system. 3. Splay The splay is the second component of a light well. A splay is the oblique transitional component of the light well that starts at the bottom of the throat and connects to the ceiling. The use of a splay will provide better light distribution into the interior space. 3a. Splay-Throat Connector The splay-throat connector attaches the splay to the throat. It can be a simple attachment, or it can incorporate an adjustable assembly that allows for horizontal, vertical, or angular displacements. 14 PIER Integrated Ceiling Systems

31 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS NOMENCLATURE AND FUNCTIONS 3b. Splay Interconnector The splay interconnector joins two pieces of splay material (e.g. gypsum board, acoustic tile, or sheet metal tubes). It may be a rigid member or an adjustable component that allows for horizontal, vertical, or angular displacements. 3c. Splay Structural Support This refers to the support that provides lateral and seismic stability for the splay. It may be a rigid brace, hanger wire, or other type of support system. 4. Light Control Devices Light control devices are attachments to the light well that modulate the amount of daylight coming through the skylight. One or more devices can be used at the same time in a light well system, depending on the design requirements. Types of light control devices are: 4a. Louvers Louvers are slanted metal slats attached to the throat that control the amount of daylight coming through. They can be installed as an integral part of the skylight frame. 4b. Interior Diffusers A diffuser is any kind of glazing material installed within the light well that diffuses the light from the exterior into the interior. The most commonly used diffusers are prismatic acrylic lenses installed at the bottom of a skylight well. 4c. Suspended Reflectors (not shown in figure) Reflectors are lighting accessories made of reflective material installed at the bottom of the light well to diffuse daylight by bouncing it off the ceiling or splay. 4d. Baffles (not shown in figure) Baffles are opaque or translucent plate-like protective shields used against direct observation of a light source. 4e. Device connectors These connectors attach the light control devices onto the throat or splay, as their design requires. 5. Suspended Ceiling A suspended ceiling is a ceiling grid system supported by hanging it from the overhead structural framing. PIER Integrated Ceiling Systems 15

32 Nomenclature and Functions Modular Skylight Systems with Suspended Ceilings 5a. Runners Runners are cold-rolled metal channels used to support ceiling tiles. 5b. Ceiling Tile A ceiling tile is a preformed ceiling panel composed of mineral fiber or similar material with good acoustical and thermal properties, and a textured finish appearance. 5c. Ceiling-Splay Connector The ceiling-splay connector joins the splay to the ceiling. It can also serve as a concealment for this junction. 6. Other Accessories The locations of these accessories were not shown in the figure and may vary depending upon their use. These accessories include: electric light fixtures, air diffusers or grills, sprinkler heads, and other devices like smoke detectors, security cameras,etc. A very important accessory that bears mentioning is a safety grate or burglar bars. This device made out of either metal wire (safety grate) or iron bars is installed inside the curb early on during construction. This device prevents workers from falling through the skylight opening during construction. This has the benefit of letting in light and letting out fumes during construction. Once the skylight is installed, if someone steps on the skylight and it breaks the fall protection or burglar bars may save someone s life. This is recommended even if the skylight is rated to withstand someone falling on the skylight, as this rating is for a new skylight and over time the skylight may become less resilient with age. 16 PIER Integrated Ceiling Systems

33 SYSTEM DESIGN This section lists the important information required to make decisions regarding the skylight well design. This design process can be applicable tp site-built system installation or for a pre-manufactured product. Design is an iterative process, and skylight system design is no exception. It requires constant refinement due to a more comprehensive and intensive design analysis, or it may be a result of feedback from other associated building systems. This leads to a better-designed skylight system and optimal daylighting benefits. SYSTEMS COORDINATION The plenum space and ceiling plane houses different building services systems, such as the structural elements HVAC, fire protection, and lighting required in a building. These elements are located in reserved horizontal strata of the plenum space. Since the light well is vertical, it cuts through all of these strata. Thus coordination of trades and industries during the design and construction phases is necessary. Figure 11. Typical spacing of systems installed within the plenum. PIER Integrated Ceiling Systems 17

34 System Design Modular Skylight Systems with Suspended Ceilings The range of spacing and dimensions for the plenum and ceiling varies according to the system used, but they will typically be within the ranges illustrated in Figure 11 and Figure 12, 20 respectively, for the building types considered here. Coordination Strategies During the Design Phase The most essential thing for a designer to remember during the design phase is to inform the project team members that skylights are to be installed in the project. The early warning allows them to make allowances in their preliminary design to account for the modular skylight well placement. Figure 12. Typical spacing of systems installed on the ceiling. 1. Designation of the Exclusion Zone The exclusion zone is the maximum penetration area of a skylight well. It will correspond to the space being occupied by the skylight well on the roof, within the plenum space, and on the ceiling. It communicates to the project designers that this zone is reserved for the light well. Any trespass into this area will require communication with the skylight designer. 2. Notation of Exclusion Zone on drawings Skylight notations should be done on the appropriate CAD drawing layer, according to guidelines set by the American Institute of Architects (AIA). 18 PIER Integrated Ceiling Systems

35 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS SYSTEM DESIGN The skylight well exclusion zone should be laid out properly on the following drawing sheets (see Figure 13): Roof plan Reflected ceiling plan Structural plan and section Mechanical plan Electrical plan 3. Specification in Contract Documents Skylight details and installation guidelines should be incorporated in the corresponding sections in specification. These should include specifications on materials, system, geometry, and installation methods. Unit skylight assembly is addressed in the Construction Specifications Institute (CSI) Manual of Practice, under the section of the trades one expects to install the light well. If the light well is part of the skylight as it is with tubular skylights then it makes sense to list the light well under unit skylights (Section 08620). If the well is made out of acoustic tile and it is expected that the ceiling installer is going to be installing the lightwell then it should go under the section for suspended ceilings (Section 09120). If one is unsure of who is going to install the lightwell one could treat the lightwell as a specialty feature in the Section s along with Section exterior sun control devices or exterior wall panel: daylighting. Coordination Strategies During the Construction Phase 1. Marking of Light Well Location On-Site During construction, the use of a marker system to block out the location of the throat and splay installation will prevent the encroachment of other building services system into the space. This space reservation can be accomplished by incorporating ribbons or similar markers in the area of the throat and splay installation, showing their approximate dimensions. 2. Proper Scheduling of Construction Activities An alternative solution is to schedule construction activities to allow throat and splay work to be completed before other building services systems. This blocks out the space required for their installation. The benefits of installing the well components early to reserve their space have to be balanced against the risk of possible damage to the light well. See Appendix for alternative scheduling solutions. Figure 13. Exclusion zone marking in plans SYSTEM COORDINATION CHECKLIST! Designate an exclusion zone that will reserve the space for the light well and the splay during the design phase and during construction.! Make sure that the skylight exclusion zone is properly designated on the following drawing sheets: roof plan, ceiling plan, structural drawings, mechanical drawings, and electrical drawings.! Incorporate skylight details and installation guidelines in the specification books to avoid skylight well coordination problems among the different trades on-site.! Mark light well locations on site to reserve space and to help coordinate with other mechanical systems. PIER Integrated Ceiling Systems 19

36 System Design Modular Skylight Systems with Suspended Ceilings DESIGN PROCESS FOR SKYLIGHT WELLS This section describes the process of designing the skylight well. The first part considers the steps involved in the process. The second part describes in detail the considerations to be taken in skylight well sizing, geometry and photometric analysis. The design process for skylight wells can be broadly categorized into two phases: the schematic design phase and the design development phase. Details regarding skylight designs are further described in Skylighting Guidelines by the Energy Design Resources 21. Figure 14 indicates the steps involved in skylight design that will then be describe each aspect of the design decisions in the following section. The next chapter then explains this design process in detail through an example. START Building characteristics 1 2 Light well design assumptions Schematic Design 3 4 Calculates SFR and well efficiency SkyCalc* Skylight spacing Are skylights spaced right? If Yes If No, revise skylight design Design Development 5 6 Refine light well and building design Is design satisfactory? Photometric analysis END If Yes Is light quality good? If Yes If No, revise skylight design If No, revise skylight design Skylight Well Design Complete Figure 14. Flowchart showing design process of skylight wells 20 PIER Integrated Ceiling Systems

37 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS SYSTEM DESIGN Schematic Design Phase The first phase of design, the schematic design phase, involves entering the following information in a skylight spacing and sizing software program called SkyCalc, 22 which can first calculate the skylight-to-floor ratio (SFR) and skylight well efficiency. This Microsoft Excel TM spreadsheet application helps building designers determine the optimum skylighting strategy that will achieve maximum lighting and HVAC energy savings for a building. SkyCalc can be used in conjunction with the Skylighting Guidelines published by the Energy Design Resources 23 to help designers select the best skylighting system for a given building. The following data should be entered in the SkyCalc program: Building details, such as building type (office/retail/school), occupancy schedule, dimensions of the rooms, and heights of roof, ceiling and plenum. Design assumptions for a skylight well, including opening size, well dimensions (throat and splay angle, width, length, and height), plenum height, and splay and throat reflectances. Check with modular light well manufacturers for light well reflectances, splay angles, and heights that they support. These light well assumptions are subject to revisions after SkyCalc calculates the results. These details are entered in SkyCalc to yield the SFR and skylight well efficiency. Spacing of skylights is then to be designed based on the SFR, room dimensions and skylight size (See the Skylight Well Sizing and Geometry section of this chapter). Design Development Phase Once the SFR and well efficiency have been calculated for the light well, the following steps are involved in the design development stage. 1. Take decisions and finalize the following design criteria: Finalize the skylight details like dimensions, number, spacing and light well reflectance. Coordinate the skylight spacing with spacing of electric light, sprinklers, and heating, ventilation, and air-conditioning (HVAC) diffusers. Decide on photocontrol set points, together with the electric lighting layout, to achieve maximum energy savings potential through skylighting. Finalize the skylight glazing characteristics, such as number of glazings, transparent or translucent, color, etc. The optical properties of the glazing materials influence daylighting quality and lighting savings. Decide on light control devices, such as louvers, reflectors, or diffusers. 2. If the spacing and sizing are not to the satisfaction of the designers, go back to the first step and revise Assumptions of Light Well Dimensions and re-enter these values in SkyCalc. If the spacing and sizing are to the PIER Integrated Ceiling Systems 21

38 System Design Modular Skylight Systems with Suspended Ceilings satisfaction of the designer, the design can proceed to the next stage: photometric analysis. 3. After the skylight well spacing and sizing are established, a photometric analysis is recommended in order to get the magnitude and direction of light falling in the room. A guide to photometric analysis is given in a later section of this chapter. 4. The lightwell space should then be reserved by representing the skylight opening and well dimensions on the CAD drawings of roof and reflected ceiling plan. The final step in the design process is to specify component requirements, such as geometry, material specification, and minimum performance standards, for each skylight component. These requirements are described in detail in the next chapter, Component Requirements. Skylight Well Sizing and Geometry The layout and spacing of skylights in a roof are important determinants for the uniform light distribution characteristics of the skylighting system. SkyCalc calculates the SFR which in turn, helps in determining the size and number of skylights in a given space. Some design aspects that drive the skylight spacing and sizing include: Roof structural spacing Ceiling height Coordination with other building systems Sizing: Large versus small skylights Splay geometry Throat geometry Roof Structural Spacing Typically, low-rise commercial buildings have either a wood or steel roof deck. In both conditions, the spacing of the secondary structural members limits the size and spacing of skylight units. 22 PIER Integrated Ceiling Systems

39 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS SYSTEM DESIGN To avoid penetrations through structural elements, skylight dimensions should be designed to be spaced in dimensions that are multiples of the secondary or tertiary roof framing modules. Figure 15. Plan showing primary and secondary structural members Ceiling Height Ceiling height is a major determinant of skylight spacing. Light distribution has to be even on the work plane. Work plane is typically measured at 30 above finished floor. The skylight spacing should be established so that there are no dark spots on the work plane due to too much distance between skylights. Rule of Thumb: Recommended center to center spacing between two skylights should be based on the following equation: ( 1.4 x ceilingheight) + ( xsplaywidth) + skylightwidth 2 Figure 16 shows spacing for skylights with splay and Figure 17 shows spacing for skylights without splay. Note that skylights without splay need to be placed closer together than skylights with splay. PIER Integrated Ceiling Systems 23

40 System Design Modular Skylight Systems with Suspended Ceilings Figure 16. Skylight spacing with splay. Figure 17. Skylight spacing without splay. Coordination with Other Building Systems Ideally for skylight spacing, the skylight designer should keep in mind the spacing layout of the electric lighting with photocontrols, sprinklers, HVAC diffusers, and ceiling tile dimensions in order to avoid site adjustments after construction. The photocontrol system should be designed such that it dims or switches light fixtures in areas with adequate daylight, while keeping the light fixtures in areas without daylight at the design output. Coordinating the daylighting and electric lighting also makes controlling the electric lighting systems more effective. Skylight Sizing The amount of daylight in a space is a factor of the size of the skylight opening and the number of skylights. These two factors trade-off each other to provide the optimum lighting conditions according to the architectural limitations set by each project. For a fixed percentage of the skylit roof area, designers could select anything from a single large skylight to many small skylights that are distributed uniformly across the roof. For the same total area, the tradeoff is typically between large skylights far apart versus smaller skylights arranged closely. 24 PIER Integrated Ceiling Systems

41 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS SYSTEM DESIGN Listed below are the advantages and disadvantages of large versus small size skylights to assist in the decision-making process. Appendix A gives a list of possible sizes of skylights and splays, and their spacing. Small Skylights More costly to install More skylights required to provide an equivalent amount of daylight More roof penetrations. A smaller light well is easier to redirect and manipulate within the plenum space Applicable for high or low ceilings Large Skylights Usually most economical to install due to lower labor and installation cost Fewer skylights are required to provide an equivalent amount of daylight Fewer penetrations, and therefore, less potential for leakage More applicable for higher ceiling heights More potential for light well to provide cut-off from glare. Small, closely spaced skylights provide more uniform lighting conditions and greater energy savings May produce bright conditions under the skylights and relatively dark conditions in between, resulting in uneven light distribution, reduced energy savings and possible glare problems Figure 18. Comparison of small vs. large skylights Many Small Skylights Fewer Large Skylights Figure 19. Many small skylights versus fewer large skylights Splay Geometry The splay geometry is governed by the decision of having a skylight with or without splay and if so, then the dimensions of the splay. Given below are some characteristics of skylights with and without splay Figure 21 shows that skylights without splay may sometimes results in dark surfaces and areas that are not daylit. Figure 22 shows that presence of splay results in better light distribution across a room. PIER Integrated Ceiling Systems 25

42 System Design Modular Skylight Systems with Suspended Ceilings Skylights Without Splay Easier and faster installation Less cost associated since no splay Light distribution not very regular More number of skylights (but smaller in size) for a given area of space Can create glare points May have brightness contrast between skylight diffuser and ceiling May not be as aesthetically pleasing as with splay Skylights With Splay No so easy installation More costs due to addition of splay Better and wider light distribution Fewer skylight (but larger in size) installations required to achieve an equivalent light level Reduces glare Minimizes brightness contrast between skylight diffuser and ceiling Aesthetically more pleasing adds to the architectural experience of space Less coordination needed with other systems Needs more coordination with other systems Figure 20. Comparison of skylight wells with and without splay. Figure 21. Skylight without splay results in darker surfaces. Figure 22. Skylight with splay has better light distribution with well-lit walls. Splay dimensions also affect skylight spacing. Wider splays produce wider light distribution and therefore require a wider center-to-center spacing. Research has shown that making the skylight splay wider than a 60 (splay angle less than 60 ) has little impact on the distribution of light PIER Integrated Ceiling Systems

43 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS SYSTEM DESIGN This is because the spread of light from a diffusing skylight is predominantly within 30 from the nadir. Typical angles of splay are (see Figure 23). SYSTEM COORDINATION CHECKLIST! Building and light well characteristics assumptions to be defined! Use SkyCalc or building energy software to determine optimum SFR based on skylight transmittance and well efficiency assumptions Figure 23. Splay angle. Wider splays increase the well efficiency of a light well for a given reflectance. (See section on Well Efficiency ) This helps reduce the skylight area needed in a space. Wider splays reduce the shielding of the underside of the skylight and can increase glare. Throat Geometry The throat geometry also plays an important role in deciding the skylight spacing and sizing criteria: The shallower a light well is relative to its width, the less light is transmitted. This is an important consideration when deciding on the height of the throat. The inside surface of the throat should ideally be a reflective material, like white paint, which will enhance the light that enters the light well. Specular materials are not recommended because of glare effects, unless the throat is shielded. A throat that has angle connectors or several offsets/wrinkles in its design (for example a tubular throat) may affect the light quality that enters the light well. The angle connectors or adjusters should be designed keeping in mind the amount of light that enters the light well (Also discussed in further detail in the Error! Reference source not found. section). Well Efficiency of a Skylight System The well efficiency (WE) of a skylight well depends on the well cavity ratio (WCR), well dimensions and reflectance of the light well material. The well efficiency of the skylight well can be calculated using the well cavity ratio equation as given by the 2005 Building Efficiency Standards: 25 Chapter Sample Project describes a detailed calculation method for well efficiency. While designing skylights, it is important to keep in mind how the well! Calculate Well efficiency of light well: Well efficiency = WE throat x WE splay x Tvis diffuser! Spacing of skylights (on center)= <1.4 x ceiling ht + 2 x splay width + skylight width (keeping in mind lighting, sprinkler, HVAC spacing)! Decision making: Finalize building and light well dimensions, skylight spacing, sizing, light well characteristics.! Coordinate with other building systems! A photometric analysis for uniformity and magnitude of light from skylights to be performed.! Reserve space: Indicate skylight opening and well dimensions in roof & ceiling plans PIER Integrated Ceiling Systems 27

44 System Design Modular Skylight Systems with Suspended Ceilings efficiency affects the quality of daylighting in a space: When the ratio of depth to width is high in a light well, the well efficiency drops. Higher well surface reflectance results in higher well efficiency. Well efficiency drops for taller light wells. More details on well efficiency can be also found in the Skylighting Guidelines 26 under the Well factor section. Room Specifications The lighting quality of the skylight system is also dependent on the room geometry and on surface reflectances of walls, floors, ceilings and furnishings. Light colored surfaces with high reflectance will help distribute brightness around the space and reduce glare potential. Light Control Devices Light controlling devices like diffusers, louvers, reflectors or clouds enhance the quality of light reaching the work surface. (See the section on Light Control Devices in the next chapter) Photometric Analysis Figure 25. Detailed skylight visualization using Radiance simulation software1. Once skylight well spacing and sizing decisions have been finalized, photometric analysis can be done using electric light design software and skylight photometric files. 27 These programs provide isolux contours (see Figure 24), light summaries, reports and rendering or visualization (see Figure 25). Lighting summaries includes average average lighting luminance in footcandles (fc) and the range (minimum-to-maximum) of lighting luminance (fc). The visualization (Figure 25) helps determine what the room looks like with a given light system. This allows one to readily identify strange patterns of light that either enhance or degrade the quality of the space. These patterns include hot spots and luminance patterns on walls or other surfaces. Figure 24 below presents an isolux contour in which the spaces below skylights are much brighter than the darker area between rows; this difference may be great enough to create discomfort in occupants. Daylighting Design Qualities Figure 24. Isolux contour. Certain aspects of light quality greatly influence both visual comfort and the experience of a space. In skylighting design decisions, two key issues the location of higher luminance areas and the uniformity of the lighting determine how well the lighting design serves the users of the space. 28 PIER Integrated Ceiling Systems

45 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS SYSTEM DESIGN 1. Luminance Luminance is the amount of visible light leaving a point on a surface in a given direction. Some guidelines to remember when evaluating luminance in building applications are: Proper placements of skylight can highlight products in retail applications. Placement of skylights can be used to highlight walls or other vertical surfaces such as the teaching wall in a classroom. To illustrate, we use the case of a retail store. Skylight placements in a daylit space need to provide the appropriate luminances on the surfaces. In the photometric analysis shown in Figure 26, skylights are used to highlight certain products on the shelves. The two sets of visualization results below show the effects of different skylight locations in providing proper light levels on the display shelves. Option 1 shows 2 skylights placed in a linear arrangement. Option 2 shows 3 skylights placed in a staggered arrangement, which gives a better distribution of light. Option 1 Option 2 Figure 26. Using photometrics to evaluate appropriate luminance levels. 2. Uniformity and glare Uniformity refers to the even distribution of light levels in a space and is a factor of daylight diffusion and skylight spacing. PIER Integrated Ceiling Systems 29

46 System Design Modular Skylight Systems with Suspended Ceilings Guidelines to remember when evaluating daylighting design for uniformity in spaces are: In office, big-box retail stores, and classroom applications where ambient lighting is required, a maximum to minimum illuminance ratio of 3:1 or less is desirable. 28 Replacing a few large skylights with many smaller skylights will increase uniformity (see Figure 19). There is a law of diminishing return however, so there is some judgment required when sufficient uniformity has been achieved. Uniformity is affected by objects inside the room. If one models a lighting system in a empty room, the uniformity of that lighting system may appear to be sufficient. Adding partitions or shelving will decrease the uniformity from lighting provided by a few large sources (such as skylights) because these objects block light travelling horizontally and thus cast shadows. Uniformity can be achieved by supplementing daylighting with electric lighting. This is especially true when lighting control zones are defined in relation to proximity to the skylight. However, many photocontrol systems adjust electric lighting levels uniformly across the space. The photometric analyses in Figure 27 show the difference in lighting effects due to the use of electric lighting. One important fact to keep in mind is that the use of electric lighting will reduce the energy savings potential of daylighting with skylights. In the image on the left, the skylights are present without electric lights, while in the image on the right, electric lights are switched on with the skylights. With electric lights Without electric lights Figure 27. Photometric analysis of uniformity due to skylights and electric lights. 30 PIER Integrated Ceiling Systems

47 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS SYSTEM DESIGN Using photometrics to refine skylight design will result in a more effective daylighting design solution. It requires a higher level of analysis, but it can make the difference between an ineffective project and a successful one. PIER Integrated Ceiling Systems 31

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49 COMPONENT REQUIREMENTS SKYLIGHT A skylight is a glazed opening in a roof to admit light. Its main functions are to transmit light, while preventing people from falling through the roof penetration and preventing precipitation from penetrating the interior space. A skylight encompasses the frame, condensation gutters, glazing, and associated connectors to the curb.these components are directly attached to a rooftop curb assembly. Figure 28. Details of a skylight. Minimum Performance Requirements The following are necessary for a skylight to perform the minimum functions as listed above: Frames should be thermally-broken to mitigate extreme temperature differences between the exterior and interior, and thereby prevent condensation. Frames should incorporate features, such as a condensation gutter, to accommodate moisture accumulation in the event of condensation. Glazing should be diffusive to avoid excessive glare in the interior space. PIER Integrated Ceiling Systems 33

50 Component Requirements Modular Skylight Systems with Suspended Ceilings The skylight frame should be attached to the curb appropriately. The skylight-curb connection should be constructed as below: The appropriate counter flashing should be included if the frame is not self-flashing. Have roof membranes installed over the curb and the frames installed over it. Fasteners should not penetrate membrane flashing, to minimize leakage problems. Skylights should be installed according to the National Roofing Contractors Association (NRCA) Roofing and Waterproofing Manual. Rails or burglar bars for fall protection and safety should be incorporated according to OSHA Design Options Glazing The type of glazing used in the skylights determine the quality of light entering a light well. Given below are some characteristics of clear versus diffused glazings. It is recommended to use diffused glazing for skylights in order to get better light transmission. Clear skylights and glass skylights are not commonly the best choice, but they may be the most appropriate solution in certain specific situations. Figure 29. Light distribution of a clear skylight. Clear Glazing Higher light transmission Higher heat transmission High glare Not so even light distribution Should incorporate other diffusing elements, like screens, louvers, baffles, interior diffusers or reflectors to improve quality of light Figure 30. Light distribution of a diffused skylight. Diffused Lower light transmission Lower heat transmission Less glare More even light distribution Can incorporate more diffusing elements for a more diffusive light quality 34 PIER Integrated Ceiling Systems

51 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS COMPONENT REQUIREMENTS Figure 31. Glass skylight. (Source: Unique Commercial Applications of Light Pipes, Ensar Group, Inc.) Glass Can only have straight surface configurations Heavier in weight Requires translucent film or light control devices to achieve a diffused light distribution Safety concerns regarding breakage Relies on sealant for watertightness More durable and more stable quality Requires slanting skylight or curbs Low-e glazing provides better control of visible light transmission, lower SHGC, and lower U-factor (refer to glossary for definitions) Plastic Can have curved or domed shapes Lighter in weight Water tightness not as dependent on sealing material Stability of glazing varies by plastic formulation Figure 32. Different skylight shapes for plastic glazing. (Source: Home Energy Magazine 1993). Double-glazed Higher light transmissivity but lower U-factor than triple-glazed Triple-glazed Higher U-factor but lower light transmissivity than double-glazed PIER Integrated Ceiling Systems 35

52 Component Requirements Modular Skylight Systems with Suspended Ceilings THROAT The throat is the element of a light well that conveys daylight from the outside to the interior space. It can also be an adjustable component that allows the light well to change in direction and location within the plenum. As explained in the Nomenclature and Functions section, the throat has two components: the structure and the surface. The throat structure refers to the components giving support and shape to the throat, such as frames, braces or hangers. The throat surface is the base material and interior finished surface providing the reflective and aesthetic properties of the light well, such as sheet metal, painted gypsum board or acoustical tile. In a splayed light well, the throat connects to the top of the roof curb or roof deck and to the top of the splay. In a non-splayed light well, it connects the skylight directly to the ceiling. A throat can also be connected to a support system, such as bracings or hangers, which allow it to satisfy structural and seismic requirements. The throat interconnectors are elements that connect two throat surfaces. They can also be simple rigid members or flexible members that will allow the throat to have horizontal, vertical and angular displacements. Figure 33. Cut section of throat. Minimum Performance Requirements The following are necessary for a throat to perform the minimum functions as listed above: The throat material should allow for easy penetration of sprinkler heads, if required by the Fire Code and/or the Fire Marshall having jurisdiction. The throat materials should be relatively fire resistant. For throats that are in return air plenums, they should have a maximum flame spread index of 25 and a maximum smoke developed of PIER Integrated Ceiling Systems

53 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS COMPONENT REQUIREMENTS The throat and its supports should have sufficient strength to support a light control device and its associated components, if required by design. The throat should allow for easy attachment of light control devices and penetration of related electrical elements, if required by design. For rigid throats, their connection to the building structure should be provided with an isolating mechanism to absorb differential movements of the light well and the building. The throat structural connection (e.g. throat connection to curb or roof. See Figure 33.) is where the throat connects to the curb or roof deck for support. It should have the following properties: For exposed light wells, structural fasteners within the throat should be concealed or finished properly. Fasteners connecting the throat to the curb are not structural elements. Other forms of structural support for the throat should be installed to carry the load of the throat and other attachments. Throat interconnectors (see Figure 33) if exposed should be properly concealed or finished. The diffuse reflectance of the throat should be greater than 80% and the specular reflectance should be greater than 90% 30. Design Options The design options for throat depend on the shape of the throat and the properties of the materials that is chosen for construction of the throat. Properties of four commonly used throat materials are described below. Material Figure 34. Lightwell made of sheet metal. Sheet Metal Overall higher reflectivity and specularity Thin and relatively lightweight Will require concealment of the well through the use of a diffuser With use of angle adapters, can easily navigate building systems within the plenum Connectors can be factoryfabricated Can be shop-manufactured PIER Integrated Ceiling Systems 37

54 Component Requirements Modular Skylight Systems with Suspended Ceilings Figure 35. Tubular light well. Source: Solatube Figure 36. Lightwell made of acoustic tiles (Source: Williams + Paddon office) Figure 37. Gypsum board lightwell Flexible Metallic Tube More flexible than a sheet metal system and can more easily navigate building systems within the plenum According structure forms light traps and can reduce the amount of daylight transmitted to interior space Connectors can be factoryfabricated Will require concealment between interior space and throat through the use of a diffuser Acoustic Tile Easier to install than gypsum board systems Inflexible and difficult to manipulate within plenum Has to be site-built More labor-intensive, but lower in cost than gypsum board construction Requires on-site bending of connectors Gypsum Board Inflexible and difficult to manipulate within plenum Nice seamless connections Requires finishing of interior surface, if left exposed to interior Will result in a heavier well system Has to be site-built Most labor-intensive system Can be exposed to interior without diffuser as a concealment if throat and skylight provide adequate diffusive qualities 38 PIER Integrated Ceiling Systems

55 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS COMPONENT REQUIREMENTS Shape Tubular Easier to manufacture Requires fewer connections Rectangular Does not require a transitional component to fit into the rectangular ceiling plane opening. SPLAY The splay is the oblique component of a light well. Its main function is to improve light distribution in the interior space. At the same time, it can also be used as a transitional element to change the light well s location, allowing it to avoid building components within the plenum or adjust its opening location to match the ceiling tile pattern. It serves as a transitional zone between the much brighter throat and the relatively darker ceiling to reduce glare effects from the skylight. Figure 38. Cut section of splay. A splay is directly connected to the throat and the ceiling system. It will also be connected to a network of support systems, such as bracing, or hanger wires, as required by structural and seismic conditions. Minimum Performance Requirements The splay should have the following properties: PIER Integrated Ceiling Systems 39

56 Component Requirements Modular Skylight Systems with Suspended Ceilings Components should be easy to replace with off-the-shelf materials, preferably in pre-cut or cut-to-size sections. Connection of structural support to surface members should be quick and easy, using pre-drilled holes, clips, or tabs. Fastener mechanism should be sufficient to hold surfaces without allowing movement. The splay should allow for sprinkler head penetration, should the design necessitate [its installation]. The splay materials should be relatively fire resistant. For splays that are in return air plenums, they should have a maximum flame spread index of 25 and a maximum smoke [developed] of If the splay is made of acoustical tiles, then splay should have a dimension that is a multiple of the ceiling tile dimension. In most cases, this will be 2 or 4. The splay should have a minimum diffuse reflectance of 80%. An interconnector should have the following properties: It should have the necessary locking mechanism to prevent movement of attached splay surfaces. It should be able to receive hangers or other structural support members. For fixed angle splays, the connector should also have a fixed angle. Splay edges should be properly concealed for a clean, seamless finish. Connections should be quick and easy, using pre-drilled holes, mechanical locks, slots, or tabs. The throat and splay connection refers to the interface between the two components of the light well: the throat and the splay. This connector should have the following properties: Geometry of the connection should be such that the top surface of the connector (5a) is parallel to the throat and the bottom surface is parallel to the splay. There should be proper concealment of the joint between the splay and the throat. Connection to the throat should be quick and easy, using pre-drilled holes, mechanical locks, slots, or tabs. The connection should allow for the attachment and removal of a diffuser, if it is required by design. It should incorporate the necessary receivers for supplementary structural support (5c). Tolerances or adjustments shall be defined in horizontal offsets, vertical offsets, and acceptance angle adjustment. 40 PIER Integrated Ceiling Systems

57 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS COMPONENT REQUIREMENTS Design Options Design options for splays depend on the properties of the splay materials. The predominant splay materials commonly used are gypsum board and acoustics tiles, described below. Figure 39. Acoustic tile splay in a classroom Figure 40. Gypsum board splay Acoustic Tile Easier to install than gypsum board systems Has to be site-built More labor-intensive, but lower in cost than gypsum board construction Inflexible and difficult to manipulate within plenum Requires on-site bending of connectors Gypsum Board Nice seamless connections Requires finishing of interior surface, if left exposed to interior Will result in a heavier well system Has to be site-built Most labor-intensive system solution Can be exposed to interior without diffuser as a concealment if throat and skylight provide adequate diffusive qualities Inflexible and difficult to manipulate within plenum LIGHT CONTROL DEVICES Light control devices are equipment-installed within the well to modulate the amount of daylight filtering through the skylight into the interior space. They accomplish this by cutting the angle of vision of the occupant or by providing more diffused light. There are different types of light control devices. These include diffusers, louvers, baffles, reflectors and their associated attachments and control systems. Minimum Performance Requirements Properties that are required of all types of light control devices are: PIER Integrated Ceiling Systems 41

58 Component Requirements Modular Skylight Systems with Suspended Ceilings They should be easily attached to the throat-splay assembly. Devices attached to the bottom of the light well should allow access to the well for maintenance purposes. Attachment should allow for tolerances in throat construction. Design Options There are commonly four main types of light control devices that designers can choose to control light levels from skylights are described below. These are diffusers, reflectors, louvers and baffles. If louvers are used, designers must also specify whether they will be manual or automatic. Figure 41. Diffusers in commercial areas Figure 42. Reflectors. uniformity Diffuser Does not require controls Can serve as a concealment for wells, therefore well structures above diffuser need not be finished Relatively inexpensive Allows the use of clear skylights Can be located at any point within the lightwell (top, middle, or bottom) Reflector Does not require controls Structural support most likely is directly or indirectly supported by roof structure or other building structural members Aesthetic addition to an architectural space Can conceal the throat installation Reduces contrast between ceiling and lightwell and thus glare Increases spacing between skylights while maintaining 42 PIER Integrated Ceiling Systems

59 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS COMPONENT REQUIREMENTS Figure 43. Louvers in an office space. Louvers Requires controls to be effective Allows control to provide different lighting levels for different uses of the space or times of day Can be mechanically-controlled or motor-actuated Often located near the skylight, and therefore, does not provide concealment for throat Baffles Similar to louvers in function Normally placed below very large skylights or roof monitors Besides light control, can be used as an architectural element Do not require controls Figure 44. Baffles in skylights in a classroom. Equipment Louver Controls Manual Can be mechanically-controlled or motor- actuated Allows for occupant control according to their preference for space quality Might result in less energy savings Time Schedule More effective function control might result in more energy savings Can be correlated to space functions according to the time of day Requires override feature for unscheduled activities SUSPENDED CEILING SYSTEM The basic function of a suspension ceiling is to provide concealment for the building systems installed within the plenum and create a more uniform ceiling plane which could be more aesthetically pleasing within the interior space. The use of acoustic ceiling panels reduces noise levels in the occupied space. PIER Integrated Ceiling Systems 43

60 Component Requirements Modular Skylight Systems with Suspended Ceilings The suspension ceiling system is connected directly to the splay or light well opening. For structural and seismic support, it is also connected to the building structure by attaching hanger wires to the required building walls. The splay-ceiling connector joins the ceiling system to the splay. It can incorporate a frame that provides concealment of the joints between the splay and ceiling. Minimum Performance Requirements The splay-ceiling connector should have the following characteristics: The top receiving surface should be parallel to the splay. The bottom receiving surface should be attached to the ceiling plane. The connector should have the necessary attachments or details for connection to the hanger wires or other structural support system. Cconnection to splay and ceiling panels should be quick and easy. The edge interface should have a clean seamless finish. The splay should adjust to fit into standard ceiling panel openings. OTHER ACCESSORIES In addition to the major light well components discussed above, there are other elements that can be incorporated in a skylight to optimize its performance. These include an electric lighting system, HVAC diffusers or grills, sprinkler heads, photosensors, smoke detectors, security cameras, and other devices. The most commonly used accessories are the fire protection sprinkler heads and the photosensors. Sprinkler heads are part of the fire protection system within a building. They are required within the throat and splay for skylight wells exceeding certain dimensions, as determined by the National Fire Protection Association (NFPA). Photosensors are electronic components that detect the presence of visible light. Information from these sensors is transmitted to a photocontrol system that dims or switches off lamps. Energy savings due to daylighting is primarily realized through the use of a photocontrol system in conjunction with skylights. Minimum Performance Requirements Sprinklers The sprinkler head installation should have the following minimum requirements: Sprinkler heads should be installed in light wells as required by the local building code authority. Lay-out should be coordinated with the fire protection engineer. 44 PIER Integrated Ceiling Systems

61 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS COMPONENT REQUIREMENTS Photocontrols When using photocontrols with skylights, the following requirements should be considered: Electric lighting circuitry should be coordinated with daylight levels within the space separate control zones for lights near skylights to maximize energy savings from an switching or dimming system. Photocontrol system should be properly calibrated and commissioned after installation. Occupants should have timed overrides of automatic switching features of the photocontrol. When photocontrols are used to control high intensity discharge (HID) lamps, the control system must account for the five minute re-strike time required between when the lamps are turned off and when they can be turned back on again. HID lamp life is also more sensitive to cycling. The photosensor location should be easily accessible for maintenance. The photosensor should not be installed in an area where it can be blocked, shaded, easily dirtied, or damaged. The photosensor location should receive light levels representative of the space. Design Options Listed below are some of the design options available for photocontrols. These are available as open or closed loops and can have the option of either stepped controls (on/off, on/50%, and on/70%/30%) or dimming controls. Photocontrols Figure 45. Open loop control scheme. Open Loop Sensor mounted so it "sees" only daylight and not changes to electric light levels Sensor best located in the light well looking up to underside of skylight Wide sensor acceptance angle so it measures average brightness of entire underside of skylight Better system to use with skylights and switching controls Less concern about excessive lamp cycling Avoids problem associated with changing reflectances in work space PIER Integrated Ceiling Systems 45

62 Component Requirements Modular Skylight Systems with Suspended Ceilings Figure 46. Closed loop control scheme. Figure 47. Stepped switching diagram. Closed Loop Sensor receives light from both daylight and interior lights, and adjusts light levels accordingly Sensor best located within the space, looking at a wall or on a task surface where reflectance will not likely change Better system to use with skylights and dimming ballasts Control must have offset (light level when lamps at full brightness) adjustment and sensitivity (how much lamps should dim in response to higher light levels) adjustment False responses can be triggered by temporary reflectance changes within the space Stepped Switching Lights are switched off or to a minimum light level in a series of discrete steps according to light levels in the space Common switching options include: on/off, on/50%, and on/70%/30% Relatively inexpensive Continuous Dimming Lights are continually dimmed according to available light levels in the space Fluorescent dimming works considerably better (in terms of saving energy)than HID dimming. Energy consumption in fluorescent lamps is relatively proportional to light output. HID lamps consume 60% of power at 25% light output and color quality diminishes Dimming often requires separate low voltage signaling wiring in addition to power circuiting Requires more expensive dimming ballasts Figure 48. Continuous dimming diagram. 46 PIER Integrated Ceiling Systems

63 PRODUCT EVALUATION AND APPROVAL This chapter describes the process of product approval for a modular skylight well system. Buildings are subject to plan reviews by building officials prior to permitting. Part of the plan review is evaluating whether products have the suitable properties according to standardized tests for compliance with building codes. These approval processes are necessary to assure that the product will not adversely affect the comfort and safety of the building occupants. CODE BODIES There are various code bodies that are responsible for approving the building products. Some of these include the Building Officials and Code Administrators International (BOCA), International Conference of Building Officials (ICBO) and Southern Building Code Congress International (SBCCI). The code body required to approve a product may differ from state to state. In California, for example, educational buildings come under the jurisdiction of the Division of State Architects (DSA), based on the California Building Code requirements. 32 However, in February 2003, the three major code bodies mentioned above were consolidated into the International Code Council (ICC). PRODUCT EVALUATION Product evaluation services previously offered by these code bodies, including the ICBO Evaluation Services, are now consolidated into the ICC-ES. Products undergoing ICC-ES evaluations will be evaluated against the most recent version of the International Building Code (IBC). Since existing building codes in the United States, including the state of California, are still based on the Uniform Building Code (UBC), evaluations for compliance with the UBC may be made for an additional fee. 33 It is recommended that manufacturers interested in marketing to states with Building Codes based on the UBC avail of this additional evaluation service. Each product will be evaluated according to Acceptance Criteria (AC) developed specifically for the product type. The Acceptance Criteria lists the PIER Integrated Ceiling Systems 47

64 Product Evaluation and Approval Modular Skylight Systems with Suspended Ceilings relevant code sections and the ASTM International tests that are required for the evaluation for the product. Acceptance Criteria relevant to the modular skylights are: AC 16 for plastic skylights AC 17 for glass skylights, and AC 78 for skylights with plastic frames For a list of code requirements listed in the AC 16 and AC 17 documents, see Appendix 5. Evaluation Reports of existing modular skylight well products indicate that the performance of the unit skylight is the overwhelming criteria for product approval. There needs to be an ICC and ICBO acceptance criteria specifically for light wells. The criteria would vary depending on the classification of light well, like whether it is located in a fire rated or non fire rated assemblies, or plenum return etc (see section Fire Ratings below) CODE REQUIREMENTS This section deals with the fire and seismic code issues to be kept in mind while designing skylight well systems, along with applicable tests associated with skylights. More information on various fire and seismic codes based on California Building code (CBC) requirements can be obtained in the research report titled Modular Skylight Well for Suspended Ceilings Research. Fire Ratings Based on the requirements to meet the fire code, three scenarios of buildings with skylight wells have been presented below. The designers can decide what category their building belongs to, based on the criteria below. It is important to note here that the code requirement for unit skylight must be met in all three scenarios, Section 2409, 2001 CBC specifies allowable skylight glazing and framing. 1. Buildings with fire rated roof/ceiling assemblies. A fire rated ceiling/roof assembly is required for certain noncombustible building types (see 2001 California Building Code). This fire rated construction is also required over some egress corridors of non-fire rated assemblies as well. The Building Code requires penetrations through a fire resistive ceiling/roof assembly, including skylight wells to be dealt with in to ways: Manufacturing a skylight well system of equivalent performance to a fire-rated shaft. Refer to Section 711 Shaft Enclosures of CBC for more details. Using non-fire-rated materials and methods for the skylight well that are either contained in, or integrated within, a fire-rated shaft enclosure. Most areas in most of the buildings in the scope of this guideline (low-rise offices, schools and retail) likely do not have to meet this most rigorous classification of roof. 48 PIER Integrated Ceiling Systems

65 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS PRODUCT EVALUATION AND APPROVAL 2. Buildings with non-fire rated roof/ceiling assembly, but with plenum returns. Many commercial buildings use plenum above the ceiling to return air back to the HVAC system instead of return air ducts. In this case, according to Section 602 of the 2003 Uniform Mechanical Code (UMC), materials exposed within ducts or plenums shall have flame spread of not more than 25 and smoke developed not more than 50 when tested as a composite product according to ASTM E84 or ANSI/UL 723". This code requirement might limit the materials used in light wells. 3. All other buildings with non-fire rated roof/ceiling assembly and no plenum return systems but lesser fire ratings. Light wells in these buildings would still have to comply with fire rating for interior finishes and unit skylights. Section 2409, 2001 CBC specifies allowable skylight glazing and framing. Chapter 8, 2001 CBC deals with fire rating of interior finishes. Insulation Location Another aspect to keep in mind while dealing with skylight well penetrations is the code requirements for insulation. With regards to skylight wells, two scenarios may be possible: 1. When insulation is located on top of the roof deck, then skylight well placed in the plenum space doesn t need to be insulated, and all light well surfaces exposed to the interior of the room may comply with fire ratings for interior finishes (Chapter 8, 2001 CBC). 2. When there is no insulation installed at the roof as is often the case when the ceiling is insulated, then the sides of the light well would have to be insulated. Seismic Rating Addition of skylight openings in the roof disrupts of the seismic diaphragm of the roof. Often, the solution is to increase the strength of the diaphragm connections via extra nailing, screwing or welding. The light well attachment to the roof and the ceiling must be designed so that it is not rigid. This would transfer movement of roof to the ceiling. There are a few things to keep in mind for seismic loads: Extra bracing is to be considered at the suspension grid supporting the acoustical tiles. Seismic requirements, according to the California Building Code relate to the installation and performance of grid systems with regard to grid strength. ASTM E and the Uniform Building Code UBC-25-2 are applicable common standards for suspended acoustical ceiling systems. The testing and standards relate to the compression and tension strength of grid connections. There are no seismic ratings or requirements for ceiling panels. Designers and structural engineers need to take into consideration the opening in the roof for skylights in their design while calculating roof structural loads. Section 2409 of CBC and deals with design loads for sloped glazing and skylights. If skylights curbs and throats are properly braced back to roof, they are not likely to be a problem. Wind loads need to be calculated by structural engineers based on type of PIER Integrated Ceiling Systems 49

66 Product Evaluation and Approval Modular Skylight Systems with Suspended Ceilings building and seismic zone. In current practices for skylights, the extra bracing is generally provided at the throat and the splay. Applicable Tests As part of compliance with the code requirements and for ICC evaluation, the skylight product has to undergo various tests. Test evaluations should be conducted by a third-party test lab complying with ICBO ES Acceptance Criteria 85 (AC 85) and accredited by the International Accreditation Service (IAS) or by an accreditation body that is a signatory to the International Laboratory Accreditation Cooperation Mutual Recognition Arrangement. For a list of testing standards required by code and ICC evaluation, see Appendix 6. FUTURE EVALUATION STANDARDS Current skylight well products in the market have a certain dimension of width and are typically of sheet metal construction (example, tubular skylights). As a result, no additional evaluation criteria were required for the skylight well performance. As mentioned earlier, Evaluation Reports of existing modular skylight well products are indicative of only the performance of the unit skylight, rather than the light well, is the overwhelming criteria for product approval. Specific evaluation criteria are needed for the light well and provide a rating for the three categories described in the fire rating section above. In these design guidelines, some future evaluation standards pertaining specifically to skylight wells are proposed. With the development of systems with bigger skylight wells with heavier and more complex components, there is a need for more comprehensive evaluation criteria to ensure that skylight wells perform in a safe manner. Some important safety issues pertaining to fire and seismic codes that should be addressed in future evaluations of skylight wells include: Seismic The evaluation process should include specific seismic code requirements for skylight wells. Well connection to structure and internal integrity should be properly designed to prevent separation or disassembly during seismic events. Well construction to structure should allow for independent movement of the roof and ceiling. Well connections to building structure and other lateral supports should be of adequate strength to ensure that the well would not fall and cause injury to occupants. 50 PIER Integrated Ceiling Systems

67 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS PRODUCT EVALUATION AND APPROVAL Fire Safety Compatibility and ease of installation of fire protection requirements, such as sprinkler head installations and smoke detection equipment in skylight wells should be addressed. An evaluation criterion for skylight wells should be developed for different classes of light wells depending upon their fire resistant rating (as mentioned in section on Fire Ratings). Materials should be evaluated for longevity and weathering effects. PIER Integrated Ceiling Systems 51

68

69 CONCEPTUAL SYSTEMS This section of the report includes a brief description of four examples of modular skylight systems design. The design process for System 1 is then described in further detail, to illustrate a step-by-step design process for a modular system outlined in the System Design chapter. SYSTEMS DESCRIPTIONS System 1: Flexible Threaded Rod (Fixed Splay) System Figure 49. Conceptual diagram of Flexible Threaded Rod (Fixed Splay) System PIER Integrated Ceiling Systems 53

70 Conceptual Systems Modular Skylight Systems with Suspended Ceilings The conceptual design of this skylight system consists of a flexible throat and a fixed splay. The flexibility in the throat can be achieved with the help of pivoted rods on four sides of the throat. Following is a brief description of each component: Pivoted Rods: These pivoted rods can help reserve the space for the throat so that the rest of the system design can be done based on these boundaries. The rods are designed to change positions if needed by being pivoted to connectors at the top and the bottom. Connectors: The connectors on the top of the threaded rod are adjustable units that allow movement of the rod according to the throat configuration. These connectors can also serve as a connection between the throat and the curb or the throat and the roof deck. The bottom connectors are L-shaped bars with slots every 3 6 where the pivoted rods are bolted. Splay: This system has a fixed splay component where no changes can be made to the splay angle or height for coordinating with other systems. Once the pivoted rods have been placed in the system, the splay can be fixed to the L-shaped bars Throat material: Once the splay has been fixed to its position, and once the pivoted rods have been adjusted based on the splay position, the throat can be constructed either out of metal, gypsum board, ceiling tiles, fabric, or other material. Construction scheduling: In the construction phase, the scheduling of activities should follow this sequence: the placement of the pivoted rods, placement of splay to ceiling tiles, and then placement of the throat. 54 PIER Integrated Ceiling Systems

71 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS CONCEPTUAL SYSTEMS System 2: Fixed Metal Throat (Adjustable Splay) System Figure 50. Conceptual diagram of Fixed Metal Throat (Adjustable Splay) System In this conceptual design, the throat is a fixed component while the splay is adjustable. However, the throat inter-connector has the flexibility to adjust to any throat height. In this example, the first stage of this system is the placement of throat, its connection to the curb/roof deck and to the throat inter-connector piece. Once the throat is placed, the asymmetric splay is then connected to the ceiling and the throat. The throat inter-connector has slots of a certain length that allows for vertical adjustment with the throat. Asymmetric splays can sometimes occur on site when the light well opening at the ceiling level doesn t correspond with the splay angle. PIER Integrated Ceiling Systems 55

72 Conceptual Systems Modular Skylight Systems with Suspended Ceilings System 3: Tubular Adjustable Throat (Fixed Splay) System Figure 51. Conceptual diagram of Tubular Adjustable Throat (Fixed Splay) System This tubular skylight concept consists of a flexible tubular throat that has the ability to be adjusted horizontally and vertically. The tubular throat is made of multiple adjusters like the curb-flashing connector, angle adapter, the main body tube, and at the bottom, the tube-to-square adapter that can be connected to the diffuser (if any) and the splay. 56 PIER Integrated Ceiling Systems

73 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS CONCEPTUAL SYSTEMS System 4: Fixed Throat Flexible Connector (Fixed Splay) System Figure 52. Conceptual diagram of Fixed Throat Flexible Connector (Fixed Splay) System This system is based on the concept of a flexible throat-splay connector. This connector can be a flexible tube or a flexible and stretchable fabric that can be adjusted to any angle, both vertically and horizontally, based on the position of the throat and the splay. Both the throat and the splay are fixed and installed at the same time based on the grid-layout. The connector is fixed to the throat and splay at the end so that it can accommodate its position based on the position of the throat and the splay. PIER Integrated Ceiling Systems 57

74 Conceptual Systems Modular Skylight Systems with Suspended Ceilings SAMPLE PROJECT This section describes a step-by-step approach to the design of one modular skylight system. The conceptual design of this skylight system has been described in the earlier section on System 1: Flexible Threaded Rod (Fixed Splay) System. Schematic Design Building Light well design assumptions characteristics 1 Calculates SFR and well efficiency Skylight spacing Are skylights spaced right? Refine light well and building design Is design satisfactory? Photometric analysis Skylight Well Design Complete Stage 1 Schematic Design The schematic design involves the input of building and light well details into the SkyCalc software to calculate the skylight-to-floor ration (SFR) and well efficiency, followed by spacing of skylights in the room. Stage 1: Building Characteristics Occupancy type: The building type used for this example is an office space in Sacramento, California. Specifications of room to be designed with skylights: An open office space 60 x 72 in size. Other room specifications include a roof height of 17, ceiling height of 11, with a 6 high plenum. The room has a floor reflectance of 20%, wall reflectance 80% and ceiling reflectance 80%. - Approximate spacing of sprinklers: 8 x 8 or 10 x 12 - Electric light layout: pendant-mounted direct/indirect fixtures Schematic Design Building Lightwell characteristics assumptions 1 Calculates SFR and well efficiency Skylight spacing Are skylights spaced right? Refine light well and building design Is design satisfactory? Photometric analysis Skylight Well Design Complete Stage 2 2 Stage 2: Light Well Design Assumptions At this stage, some assumptions are made on the number and dimensions of the skylight wells, along with a rough estimate of the SFR (equal to or less than 5% based on the energy code). These assumptions can be made based on room size, ceiling height and structural framing dimensions (see section skylight spacing and sizing ). The assumptions of the light well for this example are as follows: Skylight size: 4 x 4 Skylight well height: 6 Throat height: 3 Splay height: 3 Splay angle: 45 Diffuser: Yes (visible light transmittance of 80%) Splay and throat reflectance: 80% Number of skylights: 9 Ceiling reflectance: 80% Floor reflectance: 20% Wall reflectance: 70% 58 PIER Integrated Ceiling Systems

75 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS CONCEPTUAL SYSTEMS Figure 53. Skylight well dimensions Stage 3: SkyCalc Software Simulation The SkyCalc simulation then calculates the SFR, the well efficiency of the light well, and the total annual energy savings for that particular SFR and well efficiency of light well. Following sections give a step-by-step explanation of the SkyCalc calculation process. A. Skylight to Floor Ratio (SFR) The building characteristics and details of skylight well assumptions were input in the SkyCalc software to get the SFR and to calculate the well efficiency of the light well. The SFR, which is based on the given skylight size and number, was calculated to be 3.3%. The data entered in SkyCalc is shown in Figure 54. If the design requires an SFR of higher than 3.3%, the skylight dimensions and number can be altered. For example, for a 4 x 4 skylight size and 9 skylights, the SFR is 3.3%. If the number of skylights is increased to 12, the SFR becomes 4.4%. In order to maintain the SFR as 3.3% and increase the number of skylights from 9 to 12, the size of skylights can be reduced to 3 x 4. Schematic Design Building Lightwell characteristics assumptions 1 3 Calculates SFR, WE Skylight spacing Are skylights spaced right? Refine light well and building design Is design satisfactory? Photometric analysis Skylight Well Design Complete Stage 3 2 PIER Integrated Ceiling Systems 59

76 Conceptual Systems Modular Skylight Systems with Suspended Ceilings Figure 54. Data inputs in SkyCalc to calculate the SFR B. Well Efficiency (or Well factor) Well efficiency of a light well can be calculated using the Skycalc software or using hand calculations. The hand calculation procedure is shown in Appendix 1. The Skycalc procedure to calculate the Well Efficiency is described below taking the example of two light well conditions - Light well with splay (condition1) and light well without splay (condition 2): 60 PIER Integrated Ceiling Systems

77 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS CONCEPTUAL SYSTEMS Condition 1: Light well with splay Well Efficiency Reflectance = 99% Reflectance = 90% Reflectance = 80% 70% 60% Reflectance = 40% Well Cavity Ratio (WCR) Figure 55. Well efficiency graph Figure 56. Total well efficiency of light well with splay (WE1 x WE2 x Tvis of diffuser) To get the well efficiency of a light well with splay using SkyCalc, two separate SkyCalc runs must be made one for the throat and the other for the splay. To calculate Well efficiency of throat (WEthroat), the skylight dimensions of 4 x 4 are entered along with a well height of 3. The resulting WEthroat was calculated as 68% as shown in Figure 57 (see highlighted box in the figure). PIER Integrated Ceiling Systems 61

78 Conceptual Systems Modular Skylight Systems with Suspended Ceilings Skylights Default User Revisions Design Input Visible transmittance 59% 59% Solar heat gain coefficient 53% 53% Curb type Wood Default Wood Frame type Metal w/ thermal brk Default Metal w/ thermal brk Unit U-value (Btu/h F ft 2 ) Dirt light loss factor 70% 70% Screen or safety grate factor 100% 100% Light well reflectance 80% 80% Well factor (WF) 68% 68% Bottom of light well: Width (ft) Length (ft) Diffuser on bottom of well? No Yes, No Yes Building Default User Revisions Design Input Building width (ft) Building length (ft) 93 Change width or area 72 Wall reflectance 70% 70% Ceiling reflectance 70% 70% Floor reflectance 20% 20% Shelving reflectance 40% 40% Roof U-value (Btu/h F ft 2 ) Electric Lighting Default User Revisions Design Input Lighting setpoint (fc) Task height (ft) Lighting power density (W/ft 2 ) Fraction lighting uncontrolled 10% 0.10 Lighting schedule Office Default Office Room and luminaire depreciation 80% 80% Figure 57. Well efficiency of throat using SkyCalc Well efficiency for the splay (WEsplay) is calculated by entering the input values of 10 x 10 for the splay area (this value is to be inputted in the user revisions column in the worksheet) with a well height of 3. The WEsplay was 62 PIER Integrated Ceiling Systems

79 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS CONCEPTUAL SYSTEMS calculated as 87% (shown in Skylights Default User Revisions Design Input Visible transmittance 74% 74% Solar heat gain coefficient 67% 67% Curb type Wood Default Wood Frame type Metal w/ thermal brk Default Metal w/ thermal brk Unit U-value (Btu/h F ft 2 ) Dirt light loss factor 70% 70% Screen or safety grate factor 100% 100% Light well reflectance 80% 80% Well factor (WF) 87% 87% Bottom of light well: Width (ft) Length (ft) Diffuser on bottom of well? No Yes, No No Building Default User Revisions Design Input Building width (ft) Building length (ft) 93 Change width or area 72 Wall reflectance 70% 70% Ceiling reflectance 70% 70% Floor reflectance 20% 20% Shelving reflectance 40% 40% Roof U-value (Btu/h F ft 2 ) Electric Lighting Default User Revisions Design Input Lighting setpoint (fc) Task height (ft) Lighting power density (W/ft 2 ) Fraction lighting uncontrolled 10% 0.10 Lighting schedule Office Default Office Room and luminaire depreciation 80% 80% Figure 58). PIER Integrated Ceiling Systems 63

80 Conceptual Systems Modular Skylight Systems with Suspended Ceilings Skylights Default User Revisions Design Input Visible transmittance 74% 74% Solar heat gain coefficient 67% 67% Curb type Wood Default Wood Frame type Metal w/ thermal brk Default Metal w/ thermal brk Unit U-value (Btu/h F ft 2 ) Dirt light loss factor 70% 70% Screen or safety grate factor 100% 100% Light well reflectance 80% 80% Well factor (WF) 87% 87% Bottom of light well: Width (ft) Length (ft) Diffuser on bottom of well? No Yes, No No Building Default User Revisions Design Input Building width (ft) Building length (ft) 93 Change width or area 72 Wall reflectance 70% 70% Ceiling reflectance 70% 70% Floor reflectance 20% 20% Shelving reflectance 40% 40% Roof U-value (Btu/h F ft 2 ) Electric Lighting Default User Revisions Design Input Lighting setpoint (fc) Task height (ft) Lighting power density (W/ft 2 ) Fraction lighting uncontrolled 10% 0.10 Lighting schedule Office Default Office Room and luminaire depreciation 80% 80% Figure 58. Well efficiency of splay using SkyCalc Using the formula given below, the Well efficiency of the entire light well with splay as be calculated as: WElightwell = WEthroat x WEsplay x Tvis of diffuser = 0.68 x 0.87 x 0.80 = 47% Figure 59 and Figure 60 show the total annual energy savings and cost savings for the office space based on the well efficiency of 47%. 64 PIER Integrated Ceiling Systems

81 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS CONCEPTUAL SYSTEMS 6,000 Total Annual Energy Savings from Skylights Lighting, Cooling and Heating (all fuels converted to kwh) 5,000 Annual Energy Savings (kwh/yr) 4,000 Design 3,000 2,000 1, % 2.0% 4.0% 6.0% 8.0% 10.0% 12.0% 14.0% -1,000 Skylight to Floor Ratio (SFR) Figure 59. Total annual energy savings from skylights (kwh/yr) $900 Total Energy Cost Savings from Skylights for Lighting, Cooling and Heating Annual Cost Savings ($/yr) $800 $700 $600 $500 $400 $300 $200 $100 Design $0 0.0% 2.0% 4.0% 6.0% 8.0% 10.0% 12.0% 14.0% Skylight to Floor Ratio (SFR) Figure 60. Total energy cost savings from skylights ($/yr) Condition 2: Light well without splay When the light well has no splay, the Well efficiency of the light well (WElightwell) is the same as the WEthroat as shown in figure. In order to get the same SFR of 3.3%, the size of the skylights need to reduce from 4 x 4 to 3 x 4 and the number of skylights need to increase from 9 to 12. According to the SkyCalc calculations, the well efficiency (or well factor) of the light well without splay was calculated to be 42% as shown in PIER Integrated Ceiling Systems 65

82 Conceptual Systems Modular Skylight Systems with Suspended Ceilings Skylights Default User Revisions Design Input Visible transmittance 59% 59% Solar heat gain coefficient 53% 53% Curb type Wood Default Wood Frame type Metal w/ thermal brk Default Metal w/ thermal brk Unit U-value (Btu/h F ft 2 ) Dirt light loss factor 70% 70% Screen or safety grate factor 100% 100% Light well reflectance 80% 80% Well factor (WF) 42% 42% Bottom of light well: Width (ft) Length (ft) Diffuser on bottom of well? No Yes, No Yes Building Default User Revisions Design Input Building width (ft) Building length (ft) 93 Change width or area 72 Wall reflectance 70% 70% Ceiling reflectance 70% 70% Floor reflectance 20% 20% Shelving reflectance 40% 40% Roof U-value (Btu/h F ft 2 ) Electric Lighting Default User Revisions Design Input Lighting setpoint (fc) Task height (ft) Lighting power density (W/ft 2 ) Fraction lighting uncontrolled 10% 0.10 Lighting schedule Office Default Office Room and luminaire depreciation 80% 80% Figure 61. Well efficiency of light well without splay using SkyCalc 5,000 Total Annual Energy Savings from Skylights Lighting, Cooling and Heating (all fuels converted to kwh) 4,000 Annual Energy Savings (kwh/yr) 3,000 Design 2,000 1, % 2.0% 4.0% 6.0% 8.0% 10.0% 12.0% 14.0% -1,000 Skylight to Floor Ratio (SFR) Figure 62. Total annual energy savings from skylights-light well without splay (kwh/yr) 66 PIER Integrated Ceiling Systems

83 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS CONCEPTUAL SYSTEMS $900 Total Energy Cost Savings from Skylights for Lighting, Cooling and Heating Annual Cost Savings ($/yr) $800 $700 $600 $500 $400 $300 $200 $100 Design $0 0.0% 2.0% 4.0% 6.0% 8.0% 10.0% 12.0% 14.0% Skylight to Floor Ratio (SFR) Figure 63. Total energy cost savings from skylights-light well without splay ($/yr) Stage 4: Skylight Spacing Skylight spacing was then calculated using the rule of thumb for both conditions (light well with and without splay). Condition 1: Skylight with splay Based on the rule of thumb equation for spacing between skylights, the spacing was calculated as follows: Rule of thumb: The distance between skylights (on center) should be: < 1.4 ceiling height + 2 x splay width + skylight width ( 1.4 x 11) + ( 2 3) + 4 < x Distance between skylights with splay (on center) < 25.4 ft The following figure gives one layout option for skylight spacing layout for this condition Schematic Design Building Lightwell characteristics assumptions Calculates SFR, WE Skylight Spacing spacing Refine light well and building design Is design satisfactory? Photometric analysis Skylight Well Design Complete Stage 4 2 Figure 64. Spacing layout of light well with splay. PIER Integrated Ceiling Systems 67

84 Conceptual Systems Modular Skylight Systems with Suspended Ceilings Condition 2: Skylight without splay Rule of thumb: The distance between skylights (on center) should be: = < 1.4 ceiling height + 2 x splay width + skylight width = < ( 1.4 x11) Distance between skylights without splay (on center) < 19.4 ft The following figures give some options for skylight spacing layout for this condition. Here, the skylights are sized 4 x 4 and 14 apart but are 12 in number, with a SFR of 4.4%. In order to maintain the same SFR of 3.3%, the skylight size would have to be reduced to 3 x 4 dimensions. Figure 65. Layout without splay, 12 skylights (3 x 4 ) with SFR 3.3% Design Development Schematic Design Building Lightwell characteristics assumptions Calculates SFR, WE Skylight Spacing spacing Refine light well and Refine building design Design Is design satisfactory? Photometric analysis Skylight Well Design Complete Stage 5 2 Design Development Stage 5: Refining Design At this stage, it is important to finalize the following based on the schematic design: Finalize the skylight dimensions, number and spacing - 4 x 4 skylight opening dimensions with 24 x 20 on center skylight spacing with splay (SFR 3.3%) was finalized for this example Coordinate the skylight spacing with spacing of electric light, sprinklers, and diffusers Decide on photocontrol set points along with electric lighting layout to make maximum potential through skylighting Finalize the skylight glazing type - Double-glazing with clear prismatic lens was decided for this example Decide on light control devices like adding louvers, reflectors or diffusers - In this example, a diffuser was added to the skylight design with a visible light transmission of 80%. 68 PIER Integrated Ceiling Systems

85 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS CONCEPTUAL SYSTEMS Reserve space by representing the skylight opening and well dimensions on the CAD drawings of roof and reflected ceiling plan Stage 6: Photometric Analysis The photometric analysis was done for various conditions of the light well with and without splay, with and without electric light and on clear and cloudy day and peak daytime light conditions. Peak daytime light levels were also analyzed. An open room (no shelves) and a room with shelves were also considered for analysis. Following is a list of criteria considered for the photometric runs using Lumen Micro software program: 1. Light well with splay comparison between clear sky, cloudy and peak daytime conditions (4 x 4 skylight, 10 x 10 splay, total height of light well 6, 9 skylights in number) 2. Light well with splay and electric lights on comparison was done between direct luminaries, indirect luminaries and parabolics with T8 lamps, along with photocontrols. 3. Light well with splay in a room with shelves study of daylighting under 4. peak levels and with electric lights/photocontrols under cloudy conditions 5. Light well without splay comparison between clear sky, cloudy and peak daytime conditions (4 x 4 skylight, 10 x 10 splay, total height of light well 6, 9 skylights in number) 6. Light well without splay and electric lights on comparison was done between direct luminaries, indirect luminaries and parabolics with T8 lamps, along with photocontrols. 7. Light well without splay in a room with shelves- study of daylighting under peak levels and with electric lights/photocontrols under cloudy conditions Some broad conclusions were made based on the photometric analysis described below: An overall conclusion was made on the size of the skylights. For all conditions of light well with and without splay, the skylight size of 4 x 4 was large for the specified ceiling height. Smaller skylights would be a better solution to be considered with roughly 4 x4 as the largest size in order to obtain uniform distribution of light. Having skylights with splay allows one to use fewer and larger skylights when compared to skylights without splay. For light well with splays, a tall splay of narrow angle will provide a narrow distribution suitable for tall ceilings and a short splay with wide angle will provide a wide distribution suitable for short ceilings. At solar peak, light well without splay creates pools of light. This may not be a good design when shelves or other vertical objects subdivide the space, as it will make certain aisles well lighted but others in shadow. At solar peak light levels, splayed light wells create less distinct areas of light (more uniformity in light) than light well without splay. For open Schematic Design Design Development Building Lightwell characteristics assumptions Calculates SFR, WE Skylight Spacing spacing Refine light well and Refine building design Design Is design satisfactory? Photometric analysis Analysis Skylight Well Design Complete Stage 6 2 PIER Integrated Ceiling Systems 69

86 Conceptual Systems Modular Skylight Systems with Suspended Ceilings spaces like classrooms, light well with splays work well. In retail stores where there are shelves or other vertical objects, splays may result in shadows on aisles, though less dramatic than light well without splay. The electric lighting layouts (direct, indirect luminaries) in combination with daylight controls did not result in a favorable layout. This suggests that the most ideal daylighting solution would be with more number and smaller skylights with splay to result in uniformity. Clear Day Cloudy Day Figure 66. Photometric results for light well with splay (clear and cloudy conditions) Clear Day Cloudy Day Figure 67. Photometric results for light well without splay (clear and cloudy conditions) 70 PIER Integrated Ceiling Systems

87 MODULAR SKYLIGHT SYSTEMS FOR SUSPENDED CEILINGS CONCEPTUAL SYSTEMS Figure 68. Light well without splay in an open room in cloudy conditions Figure 69. Light well without splay with shelves at near peak daylight levels Figure 70. Skylight well with splay at near peak levels Figure 71. Light well with splay with shelves under peak conditions PIER Integrated Ceiling Systems 71

88 Conceptual Systems Modular Skylight Systems with Suspended Ceilings Figure 72. Light well with splay with shelves and indirect lighting (night time) Schematic Design Building Lightwell characteristics assumptions Calculates SFR, WE Skylight Spacing spacing 2 Design Development 5 6 Refine light well and Refine building design Design Is design satisfactory? Photometric analysis Analysis Skylight Well Design Design Complete Complete Skylight Design Process Complete Figure 73. Light well with splay with direct lighting and photocontrols (night time) Component Specifications The component specifications given below are based on the system 1 example and would vary depending on what that light well system is. Scope of Work 1. Contractor should provide all materials and labor necessary to install the whole skylight well system, including the unit skylight, throat, splay, diffusers, component interconnectors and other structural supports required to attach skylight well to the structure. 2. Other works related to skylight well installation includes: electrical, fire protection, and the suspended ceiling system. Quality Assurance 1. Contractor or manufacturer should provide documentation of product evaluation reports, such as those issued by International Code Council Evaluation Services (ICC-ES) or Underwriters Laboratory (UL) listing. 72 PIER Integrated Ceiling Systems