Guidelines for Design and Construction of Energy-Efficient County Government Facilities and Schools

Transcription

1 Guidelines for Design and Construction of Energy-Efficient County Government Facilities and Schools June 2004

2 Prepared for: Wake County Government and Wake County Public School System June 2004

3 Table of Contents This document, Guidelines for Design and Construction of Energy Efficient County Government Facilities and Schools, is organized into 4 sections. Section 1, General, introduces general energy conservation considerations such as energy budgets and goals, life-cycle costs, and selection criteria for A/E teams. Section 2, Design, is divided into 6 sub-sections, each representing a key interrelated component of energy-efficient design and contains design and good practice recommendations. The third section, Commissioning and Maintenance, offers considerations for the continuation of energy-efficient design. The last section, Appendices, offers additional information related to key energy and environmental design issues, practices and technologies. 1. General 2. Design Policy Statement Energy Goals, Budgets, Life Cycle Analysis, etc. A. Site B. Daylighting and Windows C. Energy Efficient Building Shell D. Lighting and Power Systems E. Energy Efficient Mechanical and Ventilation Systems F. Water Conservation and Plumbing Systems 3. Commissioning and Maintenance 4. Appendices A. Master List of Energy Conservation Opportunities B. Codes, Standards, and References C. Daylighting D. Typical Efficiencies of Electric Motors E. Full-Load Efficiencies F. Energy Conservation Options for HVAC System G. Maintenance and Replacement Cost H. Potential Energy Conservation Measures for Existing Buildings I. Indoor Air Quality Concerns Table of Contents

4 SECTION 1 GENERAL The Energy Conservation and Management Policy was adopted by the Wake County Board of Commissioners in 1992 in order to encourage energy efficiency and improve environmental quality in Wake County s public facilities. The policy forms the basis for the development of Guidelines for Design and Construction of Energy Efficient County Government Facilities and Schools. 1.1 ENERGY CONSERVATION AND MANAGEMENT POLICY All Wake County employees share in the responsibility for the implementation of this energy policy and must be diligent in their efforts to conserve resources and use energy efficiently. Because of the complex environmental, economic and social consequences of the use of finite energy resources, appropriate procedures must be employed in the design, construction, operation and maintenance of buildings as well as in the purchase, operation and maintenance of equipment and vehicles. Wake County shall employ appropriate staff and consultants whose assigned responsibilities include the development and implementation of energy conservation programs. The respective Energy Conservation Advisor for Wake County and Wake County Public Schools shall determine annually an energy consumption goal to be used in the preparation of facility operating budgets. Budget requests for the operation and maintenance of existing facilities equipment shall include adequate funds to maintain and enhance the operating efficiency of building systems and equipment. Proposed capital budgets shall provide for quality, energy-efficient facilities and equipment which meet or exceed the performance criteria established in the Guidelines The Guidelines, developed jointly by Wake County and Wake County Public School System, shall be periodically reviewed by the Wake County Citizens Energy Advisory Commission. The Guidelines shall include design standards, energy goals, economic assumptions for life cycle cost analysis and other building system and technology criteria. Architects and engineers shall be required to demonstrate that their designs conform to these Guidelines to the satisfaction of the professional staff of the governmental entity with primary responsibility for each project. The process of selecting teams of architects, engineers and other design consultants shall assure that design teams are fully qualified to provide the necessary professional services including the demonstrated ability to conduct the energy analysis services as indicated in the Guidelines. Professional services agreements with design professionals shall require designers to follow the Guidelines. The total design fee shall be adequate to support the requested comprehensive design services. Energy analysis shall be performed by design teams at appropriate intervals after completion of new buildings at the request of the Owner if the actual energy consumption exceeds expected energy consumption based on the initial energy analysis. This shall be considered as an additional service to be negotiated with the facility management staff and not part of the basic design services. Facilities Management staff shall develop and implement guidelines that specify procedures for the operation and maintenance of facilities during occupied and unoccupied times, and shall review guidelines annually. Section 1 - General

5 Energy use and cost data for each major facility shall be monitored monthly and reported upon request to the Wake County Citizen s Energy Advisory Commission. Data shall be reviewed annually by the staff and, at which time, goals are established for each major facility. The respective Energy Conservation Advisor for Wake County and WCPSS shall review consumption data and energy related maintenance and operational activity as presented in reports, facility audits and studies conducted during the previous year and shall prepare a report, in coordination with the Energy Commission, which recommends capital needs for energy retrofit to be considered in future building programs. The Facilities Management staff of Wake County and the Wake County Public School System shall develop specific emergency energy conservation guidelines that may be implemented in the event of an energy emergency. These guidelines shall include shut-down priorities and procedures that may be implemented during periods of energy or funding crisis and be reviewed annually. 1.2 CONSTRUCTION BUDGET The establishment of a reasonable construction budget is one of the most critical items in attaining a good quality, energy-efficient facility. An unrealistically low budget will cause problems throughout design, construction and after occupancy. A building may be inexpensive to build but may be very expensive to operate and maintain. Facility operating costs over the life of a building typically far exceed the initial capital construction cost. Therefore, long-term operating costs must be given special consideration separate from the initial goal setting for projects through each step of the programming, design and construction process. Retrofitting and renovating facilities to improve energy performance is sometimes very costly and is generally difficult; therefore it is imperative that the Design Team be responsible for performing appropriate analyses of building systems during the design phase. This approach will increase the cost for professional fees, but it will result in higher quality facilities and lower facility operating costs. A careful balance between initial construction cost and projected long range facility operating costs is an essential part of a successful public project. 1.3 ENERGY EFFICIENCY The Design Team must create an energy efficient facility that meets or exceeds energy efficient goals stated herein and still remains within the construction budget. The design must incorporate the best possible lifecycle energy solutions that provide reasonable payback periods and are serviceable by the maintenance staff. The facility should also be environmentally-sensitive and be a healthy building for employees, customers, students and visitors. Section 1 - General

6 1.4 ENERGY BUDGET AND ENERGY GOAL The most important energy programming criteria is performance. The following Energy Budgets and Energy Goals were established as benchmarks upon which to judge a project s success. The Energy Budget numbers, listed by the particular building type, reflect the minimum energy performance that is required. Achievement of the Energy Goal is considered to be excellent. These numbers were derived by analyzing standards applicable to our immediate climatic area as well as project data for local projects of similar type. BUILDING TYPE * ENERGY BUDGET (BTU S/SQ.FT/YEAR) *ENERGY GOAL (BTU S/SQ.FT/YEAR) Human Services Facilities (Clinics) 53,900 44,100 Libraries (Community Center)*** 45,100 36,900 Maintenance Buildings and Warehouses Office Buildings: - One and Two Story - High Rise Schools: - K-5 - Middle and High Schools - Gymnasiums 25,300 20,700 44,000 48,400 39,600 50,600 55,000 36,000 39,600 32,400 41,400 45,000 24/7 Facilities (see note**) (see note**) Other Building Types: (see note**) (see note**) * Energy Budget numbers reflect a value which is ten percent higher than the Building Energy Performance Standards developed by the US Department of Energy. The Energy Goals reflect values which are ten percent lower than the US Department of Energy s Building Energy Performance Standards. It includes a ventilation rate recommended by recent ASHRAE Standard ** If the building to be designed is not representative of any of the above categories, a specific Energy Budget and Energy Goal shall be developed by Wake County, with input from the Design Team. This Budget and Goal shall be established during the Programming Phase. *** Energy Budget and Goal based upon 10 hours per day 12 months per year for typical annual operation. 1.5 ENERGY STATUS REPORT The Designer must prepare and submit an Energy Status Report at each phase of the design. The reporting form, which is included at the end of the section, is intended to aid the designer in monitoring energy efficiency goals set by Wake County and Wake County Public School System. 1.6 PRIORITIES FOR ENERGY CONSERVATION STRATEGIES In addition to evaluating quantifiable, analytical results and Btu consumption numbers, there are other factors which should be considered when evaluating overall energy design. In general, it is desirable to use natural energy solutions (i.e., daylighting, passive heating and cooling) before mechanical ones. Solutions should be used which have minimal environmental impact and result in better indoor air quality. Daylighting should be considered a high priority for projects because, in addition to energy savings, productivity and health are also improved. Low maintenance solutions requirements are, obviously, the best option. Section 1 - General

7 1.7 LIFE-CYCLE ANALYSIS The purpose of a life-cycle analysis is to compare alternative design options available for the project and select the most cost-effective design option. Alternative design elements that (1) have different first costs and/or (2) will impact operating and/or maintenance costs differently must be compared using a common component. A. The life-cycle cost analysis shall include, but is not limited to, the following components: The coordination, orientation, and positioning of the facility on its physical site; The amount and type of fenestration employed in the facility; Thermal characteristics of materials and the amount of insulation incorporated into the facility design; and The variable occupancy and operating conditions of the facility, including illumination levels. B. The initial estimated cost of each energy-consuming system being compared and evaluated shall include, but is not limited to, the following elements; The estimated annual operating cost of all utility requirements; The estimated annual cost of maintaining each energy-consuming system; and The average estimated replacement cost for each system expressed in annual terms for the life expectancy of the facility. C. The life-cycle cost analysis shall be certified by a registered professional engineer or bear the seal of a North Carolina registered architect, or both as required by the respective licensing board. D. The Designer shall use the life-cycle cost analysis over the life expectancy of the facility in selecting the optimum system or combination of systems to be incorporated in the design of the facility. The energy consumption analysis of the operation of energy-consuming systems in a facility shall include, but is not limited to: The comparison of three or more system alternatives; The simulation or engineering evaluation of each system over the entire range of operation of the facility for a year s operating period; and The engineering evaluation of the energy consumption of component equipment in each system considering the operation of such components expected at expected load based on hourly weather data other than full or rated outputs. 1.8 CRITERIA FOR LIFECYCLE COST ANALYSIS A life-cycle cost analysis shall be used to evaluate the cost effectiveness of various design options to be implemented in building design. Various analytical methods have been used by designers to evaluate the appropriateness of incorporating optional energy saving measures. However, only the life-cycle cost (LCC) analysis totally evaluates what is in the best, long-term interest of the Owner. By incorporating life-cycle cost approaches throughout, all reasonable energy options can be compared on an equal level. A comprehensive LifeCycle Cost Analysis (LCCA) method for North Carolina State Facilities was issued by the North Carolina State Construction Office on October 1, This method can be downloaded at: Section 1 - General

8 1.8.1 FACTORS TO CONSIDER IN ANALYSIS The following factors should be included in a life-cycle cost analysis of various design options: Initial cost Energy operating costs Maintenance cost (over the expected life of a building) Useful life Energy inflation costs Replacement inflation costs BUILDING COMPONENTS TO CONSIDER IN ANALYSIS On the following page, Table 1-1 identifies most of the components that should be considered and analyzed by the designers in preparing life-cycle cost analysis for a project. Section 1 - General

9 Table 1-1 Building Component Architecture HVAC Plumbing Electrical Typical Alternatives Substructure Foundations Slab on grade Basement excavation Basement and retaining walls Superstructure Floor construction Roof construction Stair construction Wall Construction Increased insulation levels, insulation placement, etc. Mass (passive solar thermal storage) Daylighting Building envelope (exterior closure) type Fenestration Type, amount, and location/orientation of glass Indoor/outdoor shading devices Daylighting Interior space plan Space arrangement Circulation Finishes and colors Ceiling heights Roof construction Increased insulation levels, type of insulation Roof membrane type and color Daylighting Conveyances Selection of elevators and dumbwaiters Escalators Secondary HVAC system(s) System(s) type(s) and zoning Economizer cycle(s) Heat recovery (exhaust air, internal source, etc.) Primary HVAC system(s) System(s) type(s) and energy sources Pumping/piping configuration Heat recovery, waterside economizer cycle, etc. Thermal storage (electrical demand shifting) Plumbing system(s) Domestic hot water generation (method and energy source) Lighting Artificial lighting levels, methods, and control, including general lighting and task lighting. Daylighting Power Voltage selection (building and large equipment) Transformers (quantity, locations, efficiencies) Section 1 - General

10 1.8.3 ESTIMATING INITIAL COST FOR THE ANALYSIS The capital costs associated with an alternative include all costs that would be incurred in the design and construction of that alternative. Using the Construction Standard Institute (CSI) format, relatively accurate cost estimates can be prepared by evaluating the cost associated with various assemblies that make-up the total building ENERGY CONSUMPTION The following is a list of computer-based energy calculation software programs that engineers, architects and analysts use to model and analyze requirements for buildings. DOE-2 is a whole-building energy analysis program that calculates energy performance and life-cycle cost analysis. It can be used to analyze the energy efficiency of given designs or the efficiency of new technologies. Other uses include utility demand-side management and rebate programs, development and implementation of energy efficiency standards and compliance certification. equest (Energy Quick Simulation Tool) is based on DOE-2, but includes graphics and help wizards that provide sophisticated building energy use simulation without requiring extensive experience in the art of building performance modeling. HAP (Hourly Analysis Program) is a system design and energy simulation tool in one package. Version 4.0 of the program is Windows-based and uses a graphical user interface for input. The energy simulation module uses 1-hour time increments for a full year. This program, like TRACE 700, is designed for the practicing design engineer, but uses techniques very similar to DOE-2.1 to calculate systems performance. TRACE 700 (Trane Air Conditioning Economics) models virtually any building, any air system, any heating, cooling, or generating equipment, and any economic/utility scenario, and then helps to quickly compare them. The program takes you step-by-step from basic building parameters, such as geographic location, to complicated system modeling such as ice storage systems. TRNSYS, commercially available since 1975, is designed to simulate the transient performance of thermal energy systems. TRNSYS allows users to completely describe and monitor all interactions between system components. Because the components are written in Fortran, a user can easily generate a TRNSYS component to model any new technology that is created. Historically, TRNSYS has been used for simulating solar thermal systems, modern renewable energy systems including PV and wind power, more general HVAC systems, and buildings. The designers are encouraged to investigate other programs for use in their analyses, but programs should be submitted for approval before final analyses are performed. Finally, the construction estimate must include, as applicable, a number of costs that are sometimes overlooked by designers. They are listed as follows: Special equipment and/or rigging; Demolition; Additional architectural and/or structural requirements associated with mechanical alternatives; Additional mechanical or electrical requirements associated with architectural alternatives; Contractor Overhead (Insurance, bonds, taxes, and special conditions), typically 10-15%; and Contractor Profit, typically 4-5%. Section 1 - General

11 1.8.5 ENERGY ESCALATION RATES Each April, the National Institute of Standards and Technology (NIST) of the US Department of Commerce publishes an annual supplement to their Handbook 135. This supplement updates energy price indices. These energy price indices should be used in preparing life cycle cost analyses. Additional financial information for use in preparing LCC analyses such as inflation rates or bond financing in North Carolina are available on the State Construction Office website TIMEFRAME FOR LIFE-CYCLE COST ANALYSIS The estimated life of the measure determines the period over which the life-cycle cost analysis is to be run. If the project involves a new building, the estimated life would be longer than that of a renovated structure. Likewise, building shell component decisions should be viewed in a larger context than equipment which is often replaced by new technologies. To provide a guide for the design team, the following timeframes are to be used in the modified life-cycle analysis. This modified approach (which multiplies the projected life of the facility time a factor or percentage) reflects a balance between what is best for the life of the facility and the importance of keeping initial cost low. Type Of Measure New Construction Building Shell (Thermal Envelope) Office Buildings, Schools, Libraries, Gymnasiums Maintenance Facilities Mechanical Equipment, Electrical, Lighting and Controls Renovation Building Shell (Thermal Envelope) Office Buildings, Schools, Libraries, Gymnasiums Maintenance Mechanical Equipment, Electrical, Lighting and Controls Projected Life Of Facility 50 years 30 years 30 years * * * * Timeframe For LCC Analysis (% And Years) 50%, 25 years 50%, 25 years 50%, 15 years 50%, 15 years 50% * 50% * 50% * 50% * * On renovation projects, Wake County and the design team will determine the projected remaining useful life of the facility or equipment. This projected life figure should be multiplied by the percentages listed above in order to determine the actual number of years to use in the modified life-cycle cost analysis. Section 1 - General

12 ENERGY STATUS: SCHEMATIC DESIGN REPORTING FORM Project Project # DATE... Submitted By Building Type K-5 School Middle School High School Library Fire/EMS station Office Bldg Detention Facility Judicial Bldg Maintenance Office Bldg Renovation Other Square Footage Conditioned Total Project Design Team Energy Consumption Architect Lighting / Electrical Engineer Mechanical Engineer Energy Budget Energy Goal Energy Projection The analysis of energy consumption is based upon computer simulation of the facility:... Btu/Square foot/year. Btu/Square foot/year....btu/square foot/year % of Consumption Btu/Square foot/year Heating.%. Cooling %. Ventilation/O.A.*. %. Interior Lighting. %. Other Electrical %. Hot Water %. Other %. Total Building 100% Exterior Lighting and other loads % Total Facility 100% * Assume 15 CFM/person ventilation rate Time Frame for Life-Cycle Cost Analysis New Construction.. Renovation. Projected Life Of Facility Years Energy (And Daylighting) Computer Software Program(S) Used Electrical Service Requirements Single phase Three-phase Anticipated Energy Sources and Systems To Be Used Fuel/Energy Source HVAC/Lighting/HW System Description Heating... Cooling... Hot Water... Lighting... Fire Pump... Generator...

13 ENERGY STATUS: DESIGN DEVELOPMENT REPORTING FORM Project. Project # DATE... Submitted By Building Type K-5 School Middle School High School Library Fire/EMS station Office Bldg Detention Facility Judicial Bldg Maintenance Office Bldg Renovation Other Square Footage Conditioned Total Project Design Team Energy Consumption Architect Lighting / Electrical Engineer Mechanical Engineer Energy Budget Energy Goal D.D. Energy Projection S.D. Energy Projection The analysis of energy consumption is based upon computer simulation of the facility:... Btu/Square foot/year. Btu/Square foot/year....btu/square foot/year....btu/square foot/year % of Consumption Btu/Square foot/year Heating.. %. Cooling. %. Ventilation/O.A.*.. %. Interior Lighting. %. Other Electrical... %. Hot Water %. Other. %. Total Building 100 % Exterior Lighting and other loads % Total Facility 100 % * Assume 15 CFM/person ventilation rate Time Frame for Life-Cycle Cost Analysis New Construction.. Renovation. Projected Life Of Facility Years.. Energy (And Daylighting) Computer Software Program(S) Used Electrical Service Requirements Single phase Three-phase Anticipated Energy Sources and Systems To Be Used Fuel/Energy Source HVAC/Lighting/HW System Description Heating... Cooling... Hot Water... Lighting... Fire Pump... Generator...

14 ENERGY STATUS: CONSTRUCTION DOCUMENTS REPORTING FORM This form will be used for 60% Construction Documents Phase as well as 100% Construction Documents Phase. Project Project # DATE... Submitted By Building Type K-5 School Middle School High School Library Fire/EMS station Office Bldg Detention Facility Judicial Bldg Maintenance Office Bldg Renovation Other Square Footage Conditioned Total Project Design Team Energy Consumption Architect Lighting / Electrical Engineer Mechanical Engineer Energy Budget Energy Goal C.D. Energy Projection D.D. Energy Projection S.D. Energy Projection The analysis of energy consumption is based upon computer simulation of the facility:... Btu/Square foot/year. Btu/Square foot/year....btu/square foot/year....btu/square foot/year....btu/square foot/year % of Consumption Btu/Square foot/year Heating %. Cooling.%. Ventilation/O.A.*.%. Interior Lighting..%. Other Electrical.%. Hot Water. %. Other..%. Total Building 100 % Exterior Lighting and other loads % Total Facility 100% * Assume 15 CFM/person ventilation rate Analysis Completed During Construction Documents Please explain any variance from previous energy consumption projections Maintenance Please explain the building maintenance ramifications of energy-saving features which require high maintenance.

15 ENERGY STATUS: BIDDING PHASE REPORTING FORM Project Project # DATE... Submitted By.. Building Type K-5 School Middle School High School Library Fire/EMS station Office Bldg Detention Facility Judicial Bldg Maintenance Office Bldg Renovation Other Square Footage Conditioned Total Project Design Team Energy Consumption Architect Lighting / Electrical Engineer Mechanical Engineer Energy Budget Energy Goal Bidding Phase Energy Projection C.D. Energy Projection... Btu/Square foot/year. Btu/Square foot/year....btu/square foot/year....btu/square foot/year The analysis of energy consumption is based upon computer simulation of the facility: % of Consumption Btu/Square foot/year Heating %. Cooling %. Ventilation/O.A.* %. Interior Lighting %. Other Electrical %. Hot Water %. Other %. Total Building 100 % Exterior Lighting and other loads.% Total Facility 100 % * Assume 15 CFM/person ventilation rate Status Report Please explain any variance from previous energy consumption projections that may result from accepted alternates/change orders/modifications during construction..

16 A. SITE 1. General Decisions made early in the design can often have a significant impact on many other aspects of the design. By orienting a building effectively, designers can maximize solar access and boost the effectiveness of daylighting strategies, reducing the need for electrical lighting as well as heating and cooling loads. Orienting the building linearly on an east-west axis is one important example. By maximizing well-controlled, south-facing glass and minimizing east- and west-facing glass, the energy performance is greatly enhanced, comfort conditions are improved, and initial costs associated with cooling are reduced. 2. Selecting a Site When selecting a building site, the highest priority should be given to sites that enable the building to be cost-effective and resource efficient. a. Consider the rehabilitation of an existing site or an urban in-fill area before choosing an undeveloped site. b. Select a site that can maximize solar access for daylighting and other solar systems and minimize east and west glass. c. Consider the availability and cost of utilities and infrastructure required to develop the site. d. Analyze mass transit and pedestrian accessibility as well as potential bus routes in the area. e. Consider the topography, the soil conditions and the probability of encountering subsurface rock or other unsuitable soils. 3. Building Orientation To minimize energy use, maximize energy-saving potential by siting the building appropriately. a. Elongate the building on an east-west axis when possible. b. Develop a building design that minimizes east and west-facing glass. c. Employ one-story designs, when possible (and cost-effective), to maximize the potential for daylighting. In multiple-story buildings, minimize the depth of the rooms to maximize the daylighting contribution. 4. Maximize Site Potential Evaluate ground conditions at the site since this typically determines, to a great degree, both the economic and environmental success of the design. a. Establish floor grades that least impact site grading. b. Consider existing trees and new landscaping as a means of providing shading in the warmer months. c. Stockpile appropriate rock from site development for late use as ground cover. Site

17 B. DAYLIGHTING AND WINDOWS 1. General a. Of all the high performance design features typically considered, daylighting may have the greatest impact on Wake County facilities. Optimum daylighting design significantly reduces energy consumption and also creates improved learning and working environments. Daylighting has been shown to result in increased attendance, improved grades for students, and increased productivity of the occupants. When properly designed, windows, clerestories, and roof monitors can provide a large portion of the lighting needs without undesirable heat gain or glare. b. Electric lights produce more waste heat energy than daylighting, for the equivalent lighting effect. Waste heat must be removed in warmer months through ventilation or air conditioning, using additional energy. Sunlight, on the other hand, is a cooler light. Reductions in cooling loads due to daylighting strategies often enable designers to downsize air conditioning systems, reducing the initial cost of equipment. High performance windows help to minimize heat gain in warmer months and heat loss in colder months. Although windows can create glare and skylights may cause overheating, properly designed daylighting strategies can reduce both lighting and cooling energy consumption. Glare can also be controlled through good design practices. Effective Daylighting strategies reduce both lighting and cooling loads. 2. Building Orientation and Solar Access a. By elongating the building design on an east-west axis, the potential for cost-effective daylighting is maximized. b. Consider daylighting strategies using south- or north-facing glass. This makes unwanted, excessive radiation much easier to control. An elongated building that has its major axis running east-west will also increase the potential for capturing winter solar gain as well as reducing unwanted summer sun that more often strikes on the east and west surfaces. Exposed, eastern- and western-facing glass should be avoided wherever possible because it will cause excessive summer cooling loads. South glass should incorporate properly sized overhangs, lightshelves or shading techniques that limit radiation in warmer months and prevent direct sun at critical cooling times of day. Daylighting and Windows

18 To optimize solar access, develop a building plan elongated along an east-west axis. c. Verify that other exterior design elements or existing site features do not negatively affect the daylighting design. d. Make sure other building elements are not inadvertently shading glazing areas that are designed as daylighting elements. e. Consider the reflectance of the materials in front of the glazing areas. The use of lighter roofing colors can reduce the glass area needed for roof monitors, while a light colored walkway in front of a lower window may cause unwanted reflections and glare inside areas of a building. 3. Daylighting Design Strategies a. Because lighting is a significant component of a building s energy consumption, efforts to use daylighting should be given a high priority. 1) Good daylighting design can reduce the electricity needed for both the lighting and cooling needs of a building. Daylight provides a higher ratio of light to heat than electrical sources. This ratio, known as lighting efficacy, is much higher for daylight than for electric light sources, meaning that daylight provides more light and less heat, greatly reducing cooling loads. The following chart compares the efficacy of various light sources. Lighting Efficacy Efficacy Lighting Source (Lumens/Watt) Beam Sunlight / Diffuser Skylight High Intensity Discharge (high pressure sodium, metal halide) Fluorescent Compact Fluorescent Incandescent Sunlight provides more lumens/watt then electrical lamps Source: Lawrence Berkeley National Laboratory Lighting Market Source Book for the United States Daylighting and Windows

19 2) Consider daylighting apertures to limit the amount of direct beam radiation entering during the hottest part of the day in the cooling season. This would mean that east- and west-facing glass should be minimized. South-facing vertical glazing is typically better because roof overhangs can be designed to effectively admit low-angle winter radiation for daylighting while excluding excessive higher-angle sunlight in the warmer months. North glazing is second best because it doesn't create overheating problems during the cooling seasons but it also doesn't provide any passive heating benefits. 3) Consider using a well-designed overhang to mitigate the potential drawbacks of summertime solar gains through south-facing glazing. An oversized overhang on the south is not recommended on daylighting apertures since it can also block significant amounts of diffuse radiation in addition to the direct beam. 4) Develop a daylighting design with primary emphasis on south- (typically best) or north-facing roof monitors and a secondary emphasis on south-facing lightshelves. Lightshelves can significantly enhance the natural lighting uniformity within a space and also provide good lighting in narrow rooms (less than 16 feet to 20 feet). Lightshelves may also be the only practical option on multiple-story buildings. 4. Roof Monitors and Clerestories a. Roof monitors should be considered to typically perform two critical functions: they provide uniform light within the room, and they eliminate glare. 1) Design daylighting strategies to meet the different lighting needs of each major space while accounting for: a) differing lighting level requirements by time of day; and b) the ability to darken particular spaces for limited periods of time. 2) If south-facing roof monitors are employed, they should: a) employ baffles within the light wells to totally block direct beam radiation from striking people, reflective surfaces, or computers; b) block high summer sun with exterior overhangs; and c) reduce contrast between very bright surfaces and less bright areas. 3) Optimize the design of roof monitors to enhance their benefits. a) Minimize size and maximize transmission of glass to reduce conductive losses and gains. b) Develop an overall building structural design that integrates the daylighting strategies and minimizes redundant structural elements. c) Consider clear double glazing or clear double glazing with argon for south-facing windows. Daylighting and Windows

20 d) Choose light-colored roofing materials in front of roof monitors to reflect additional light into the glazing. e) In roof monitor/lightwell assemblies, consider incorporating white (or very light-colored) baffles that run parallel to the glass and are spaced to ensure that no direct beams can enter into the space. These baffles should be fire-retardant and UV resistant. Using light-colored translucent baffles reflects the sunlight into the space and eliminate contrast from one side of the baffle to the other. f) At the bottom of the lightwell, consider providing a transition between the vertical plane surface and the horizontal by introducing a 45 degree transition, if possible. This will decrease the contrast between the higher light level inside the lightwell and the horizontal ceiling. g) Ensure that the walls and ceiling of the roof monitor are well insulated and incorporate appropriate infiltration and moisture barriers. 5. Lightshelves a. Consider the use of lightshelves made of a highly reflective material that can bounce the sunlight that strikes the top of the surface deep into the building. The reflected sunlight will hit the ceiling and, in turn, provide light for the room. This is an effective strategy for rooms up to 20 feet deep and can be employed in multi-story buildings or where roof monitors are not possible. Using lightshelves on south-facing windows allows natural light to bounce deep into the room. b. Select durable materials, capable of carrying the weight of a person, for both interior and exterior lightshelves. c. Consider aluminum exterior lightshelves as a good compromise between good reflectance, little or no maintenance, and cost. Daylighting and Windows

21 d. Consider incorporating white painted gypsum board on top of interior lightshelves. Aluminized, acrylic sheets applied to the top of the shelf allow light to bounce further back into spaces and can improve performance in deeper rooms without top lighting. e. Use blinds as a strategy to enhance the performance of lightshelves. f. Consider controlling the windows located above and below the lightshelves independently. On the south faåade, daylighting can be enhanced by incorporating vertical blinds that focus radiation to the perimeter walls within a space and away from people within the space. 6. Lighting Controls Lighting controls can ensure that occupants always have adequate light while energy efficiency is maintained. Enhance the economic benefits and provide for smoother transition between varying light conditions by implementing multi-staged or dimmable lighting controls. 7. Interior Finishes 1) Provide sensors mounted in a location that closely simulates the light level (or can be set by being proportional to the light level) at the work plane 2) Implement a fixture layout and control wiring plan that complements the daylighting strategy 3) Provide means to override daylighting controls in spaces that are intentionally darkened for special uses or presentations.. a. The color of interior finishes will have a dramatic impact on the lighting requirements within the space. 8. Skylights 1) Consider using white (or very light colored) paint inside the lightwell area. 2) Apply carpet or other floor coverings that are as light as is practical for maintenance. This will greatly enhance reflectance and require less glazing to produce the same light levels. 3) If there are television monitors, computers, or whiteboards in the classrooms, consider locating them so as to minimize glare. 4) Enhance the daylighting by considering placement of south-facing windows with lightshelves close to perpendicular interior north-south walls. a. Consider skylights if they can be specifically designed to avoid overheating during the cooling season and perform well with minimum maintenance. 1) If skylights are used, specify those that incorporate: a) motorized, louvered systems that seasonally and hourly adjust to allow the optimum amount of radiation to enter the glazing; and b) a means to reduce glare and diffuse the radiation once inside the space. Daylighting and Windows

22 9. Windows a. Windows have a significant impact on energy consumption. The characteristics of the windows and their location, orientation, design, and purpose will determine, to a great degree, the level of energy-efficiency the facility achieves. b. In all cases, windows should be made of high-quality construction, incorporate thermal breaks, and include the appropriate glazing for the particular application. To determine the optimum glazing for each application, the designer should conduct computer simulations that compare options. The US Department of Energy s DOE-2 program is one of the better analytical tools available for this purpose. Solar Transmission Values for Typical Glass Types Glazing Type Solar Transmission Equivalent U- Value Clear, Single 75%-89% 1.11 Clear, Double 68%-75% 0.49 Low-e, Double, Clear 45%-55% 0.38 Low-e, Tinted, Grey 30%-45% 0.38 Low-e, Argon 45%-55% 0.30 Considering the transmission values of glass by orientation can greatly reduce cooling loads. c. Analyze and select the right glazing for each orientation, location, and purpose. If windows are: 1) Oriented east and west and not externally shaded, the best choice is to use a tinted glazing with low-e or low-e with argon. 2) Well-shaded by building elements (e.g., overhangs) or north-facing, tinting is not advised since it restricts the transmission of diffuse radiation. 3) Located close to the floor, comfort becomes a more critical issue and low-e or low-e windows with argon glazing are appropriate. 4) Designed as daylighting components above lightshelves or in roof monitors, the best option is typically clear double glazing or clear double glazing with argon. Window Selection Considerations Application Exposure Type South clear double, low-e with argon View Glass North clear double, low-e with argon (non-daylighting apertures) East/West, unshaded Tinted, double, low-e with argon East/West, shaded clear double, low-e with argon Windows Above Lightshelves South Clear double or clear double with argon High Windows above view glass North Clear double or clear double with argon Roof Monitors South Clear double or clear double with argon The intended application and exposure of a window determines appropriate window selection. Daylighting and Windows

23 5) For non-daylighting apertures, consider selecting spectrally selective, low-solar gain, low-e glazing glass. 6) If no other external shading is implemented, tinting glazing can be considered as a means of reducing excessive solar gain. 10. Exterior Window Treatments The most efficient means of appropriately restricting unwanted solar gain from entering glass areas is to block the radiation before it gets to the glazing. 1) Properly-sized, fixed overhangs on south-facing roof monitors and lightshelf glazing block a large portion of the mid-day summer sun while still allowing the lower winter sun to reach the glass. 2) Incorporate overhangs or other design elements above east- and west-facing glazing so that they effectively block the morning and afternoon sun. 3) Consider the advantages of using seasonally adjustable or stationary awnings, solar screens, shutters, or vertical louvers when fixed overhangs are not possible or are impractical. Transmission of light is greatly impacted by the type of window treatments used. 11. Interior Window Treatments If exterior window treatments can not effectively control the seasonal and daily variations in radiation (and resulting glare), or if it is necessary to be able to darken the particular space, blinds or shades may be considered. Daylighting and Windows

24 C. ENERGY-EFFICIENT BUILDING SHELL 1. General a. Because the building shell is typically responsible for 10% 20% of the total energy consumed in a building, focusing on this area of design is an important component of energy-efficient design. Increased insulation in the walls and ceiling helps to reduce heat loss and improve comfort. Light-colored exterior walls and roofs help to reduce cooling loads. These factors also contribute to reducing the size and cost of the HVAC system required. The useful life of building materials, systems, and equipment incorporated in buildings can vary considerably, so the building shell decisions the designer makes will impact the first cost of the building as well as the long-term costs associated with operation, maintenance, and replacement. b. Wall insulation should be selected based on the likelihood that it will never be replaced. When selecting wall and roof systems, it is critical that the designer choose what is best for the entire life of the facility. Consider specifying interior and exterior finishes that are durable and as maintenance free as possible, and integrate insulation levels that are appropriate for the life of the facility. Also, incorporate durable strategies that prevent air infiltration. High-mass exterior walls, light colored roof finishes, and window treatments including lightshelves and lowglazing for view windows are among the energy-efficient building shell elements. e Energy-Efficient Building Shell

25 2. Massive Wall Construction a. High-mass construction techniques have been historically employed to moderate the heat gain experienced during the hot days, delaying the impact until nighttime when ventilation strategies can cool the interior spaces. If adequate mass is incorporated, these strategies are just as effective today, particularly since county facilities are typically not occupied during evening hours. b. Employing a high-mass wall construction technique, such as 16" brick-block and blockblock cavity walls with rigid cavity insulation or adobe construction with insulation, thermal gains can be delayed by up to 12 hours. c. Newer wall systems using insulated concrete forms or tilt-up insulated concrete panels have also proven effective. Heat Gain Lags in High-Mass Walls Using high-mass wall construction techniques can delay thermal gains by up to 12 hours. Energy-Efficient Building Shell

26 3. Moisture and Infiltration Strategies a. Controlling air flow and moisture penetration are critical elements in reducing energy consumption, maintaining structural integrity, and ensuring a healthy indoor environment. b. Air flow retarders should be installed on the exterior of the building, and building assemblies should protect the outside wall surface from getting wet. Any moisture should be allowed to drain away or dry towards the interior, using permeable interior wall finishes and avoiding wall coverings. c. Since air leakage can carry significant amounts of moisture into the building envelope, caulk and seal any building shell penetrations and tape the joints of insulating sheeting per the manufacturer s recommendation. 4. Insulation Strategies a. Evaluate the cost-effectiveness of varying insulation R-values to maximize long-term benefits. b. When selecting insulation levels, refer to ASHRAE Standard R-values required by local building codes should be considered a minimum. c. When determining the choice of insulation, the designer should consider energy efficiency, initial cost, and long-term performance. Insulation products carefully considered for stability of R-value over time, and comparisons based on the average performance over the service life should be made. 5. Interior Finishes a. By properly selecting light-colored interior finishes, lighting energy demands can be reduced and visual comfort can be improved for no additional cost. b. Select light colors for interior walls and ceilings to increase light reflectance and reduce lighting and daylighting requirements. c. Consider the color and finish of interior finishes. Light colored, glossy finishes can create glare problems that negatively impact visual comfort. Energy-Efficient Building Shell

27 6. Stopping Radiant Heat Gains a. Creating a building shell that is massive and well insulated can effectively address conduction gains and losses, but it is critical to also consider radiant solar gains. In the warmer months, up to 90% of the cooling load coming from the roof area can be attributed to radiant heat gain. The designer should address this problem to decrease the cooling load significantly. b. Consider incorporating radiant barriers in the roof assemblies to reduce up to 95% of the radiant heat gain. When solar radiation strikes a roof, a certain percentage of radiation is reflected away and the balance is absorbed. When this occurs, it heats up that material and the material re-radiates downward. The low-emissivity properties of the aluminum in the radiant barrier stop this radiant process, allowing only 5% of the radiation to pass through. Radiant barriers that have coatings to protect against oxidation help ensure long-term performance. These types of radiant barriers are superior to reflective roofing strategies that tend to lose their reflective qualities over time. Dust accumulations on radiant barriers reduce their performance. When possible, they should be suspended from the joists or rafters to reduce dust accumulation. Radiant Heat gain can be responsible for 90% of the heat entering through the roof. The use of a radiant barrier can block up to 95% of this gain. Energy-Efficient Building Shell

28 c. To reflect solar gain away before it can create negative radiant impacts within the spaces below, incorporate highly reflective roofing systems. This strategy is important, particularly in areas where radiant barriers can not practically be installed. d. Consider selecting a light color for the exterior finish to reflect solar radiation. e. Consider shading exterior walls with architectural elements (or landscaping) to minimize the solar radiation that reaches the building shell. Energy-Efficient Building Shell

29 7. Embodied Energy a. When selecting building materials, consider that the amount of energy embodied in constructing the building typically exceeds two decades of energy consumption. To address the overall impacts of energy consumption, consider the energy involved in making each product, transporting the product to the site, and implementing the component into the building. b. Because often half or more of the energy involved in constructing a building is related to transportation of materials, consider selecting locally made products and construction materials. c. Consider the energy used in the manufacturing of materials and products incorporated in the building. d. Consider the use of recycled products. e. Evaluate the recyclability of construction materials once the building has passed its useful life. f. If existing structures on the building site are to be demolished, consider how the typically wasted materials could be used in the new construction. Energy-Efficient Building Shell

30 D. LIGHTING AND POWER SYSTEMS 1. General a. The design of a building s lighting system has direct bearing on the performance of the occupants. The ability to perform visual tasks is strongly impacted by the type and quality of the lighting systems implemented. Lighting strategies that reduce glare while still producing the required lumen levels are essential components of a high performance energy efficient building. b. Lighting represents 25%-40% of a typical building s energy costs. An energyefficient lighting system can save thousands of dollars annually in just one building, because improving the efficiency of the overall lighting system reduces the energy requirements for both lighting and air conditioning. The use of automated controls in daylit spaces can automatically decrease or increase light levels as needed, and occupancy sensors can automatically turn off lights in unoccupied spaces. 2. Lighting Design Strategies a. The design team should create an energy-efficient, high-quality lighting system by typically following these three strategies. 1. Select efficient lamps, ballasts, lenses and fixtures that address the needs of each space and achieve the highest output of lumens per input of energy. 2. Provide occupancy sensors, electric timers, and other controls that limit the time the lights are on to only those hours when the space is occupied and the light is needed. 3. Provide automated daylighting controls that reduce or dim the electrical lighting when sufficient natural light is present. b. Review current ASHRAE Standard to establish lighting power densities (LPDS) for each space within the facility. ASHRAE was used to prepare these guidelines. c. In naturally lit spaces, the artificial lighting design should be compatible with the objectives of the daylighting. In non-daylit spaces, the objective should be to implement the most energy-efficient system possible that minimizes glare while providing the proper level of quality light. These objectives can be achieved by: 1. Maximizing illumination by considering the geometry and reflectances of finishes in each space. 2. Consider indirect lighting strategies as a way to complement daylighting. 3. Consider fixtures that are designed to minimize glare, particularly in rooms with computers. 4. Consider providing low-level ambient lighting supplemented by task lighting. Lighting and Power Systems

31 5. Consider photovoltaic lighting systems for remote exterior applications such as greenways, parking lots, and walkways. It is often more costeffective to use a localized photovoltaic system with its own battery storage than to provide underground electrical service to a building located more than 100 yards away. d. Consider daylighting that could reasonably be incorporated in the overall design. 1. If significant daylighting is to be incorporated and the space is typically unused at night, consider standard back-up lighting systems in the daylit spaces. Because the amount of time that the electrical lighting is on will be minimal, it may be difficult to justify the more energy efficient, state-ofthe-art, lighting strategies. 2. If daylighting is not possible within well-used spaces, compare various lighting and ballast combinations to determine the optimum design. 3. In conjunction with daylighting analyses, evaluate staged and dimable controls, staged lighting levels tied to a photocell that operates banks of lights in one to four stepped increments, and dimmable lighting, individually controlled by dedicated photocells. e. Minimize glare and eyestrain by: 1. evaluating the location of the lighting sources and the occupant s field of view; 2. avoiding glare problems commonly experience when viewing computer screens; 3. minimizing situation of transient adaptation where the eye can not properly adjust when going from one space to another with drastically different light levels; and 4. considering indirect lighting systems. 3. High-Efficacy Lamps 1. Efficacy is an important measure for energy-efficiency in light output per unit of energy used. High-efficacy lamps can provide the same illumination and color rendition as standard lamps, but at two to six times the efficiency. 2. To maximize efficacy, minimize the use of incandescent fixtures. Standard Incandescent 3. When selecting lamps, Tungsten Halogen consider Halogen Infared Reflecting maintenance and lamp Mercury Vapor replacement costs. Compact Flourescent (5-26W) Compact Flourescent (27-40W) Full Size & U-Tube Fluorescent Metal Halide Compact Metal Halide Lighting and Power Systems High Pressure Sodium White Sodium Lamp Plus Ballast (Lumens/Watt)

32 Figure illustrates different lamp efficiencies 4. Select the lamps with the highest lumens of output per Watt input that addresses the specific need. 4. Fluorescent Lamps Lamp Type T-5 Fluorescent (28Watts/4Ft) T-5 HO Fluorescent (54Watts/4Ft) T-8 Fluorescent (32Watts/4Ft) T-12* Fluorescent (34Watts/4Ft) Fluorescent Lamp Technologies-Efficacy Comparisons Lamp Lumen C.R.I. Lumen Ballast Description and comments Life /Watt Maint.* Factor /8 dia. Tube; high lamp and ballast efficiency, high CRI, similar output to T-8 with a 12% reduction in power usage /8 dia. Tube; high lumen output, high CRI, 88% higher lumens than standard 4 Ft. T dia. Standard for efficient fluorescent lamps 23% efficiency improvement over T É dia. Tube, still being used where efficiency is not being considered** Developed by Padia Consulting from manufacturer s literature (Philips, Osram Sylvania, General Electric) * The lumen maintenance percentage of a lamp is based on measured light output at 40% of that lamp s rated average life. For T-5, after 8,000 hours of life time, the lumens/watt will be 98.8 lumen/watt (104x0.95) Fluorescent lamp selection should be based on the illumination needs of the area and lamp replacement frequency and cost. **Note: T-12 should not be specified for County and School Projects. Lighting and Power Systems

33 a. Consider the smaller diameter T-8 and T-5 fluorescent tubes over the traditional T-12s because they have a higher efficacy. The T-8 system produces 92 lumens per Watt as compared to 69 lumens per Watt for the T-12 system. The T-5 system produces 33% more lumens per Watt than the T-12 system. b. Consider fixtures that are designed to enhance the efficacy of the T-8 and T-5 lamps by incorporating better optics in the luminaire design. The graph compares efficacies of common fluorescent lamp/ballast combinations with the efficacy of a tungsten halogen lamp. 5. Compact Fluorescent Lamps a. Consider compact fluorescent lamps that are energy efficient and long lasting. A 13-Watt compact fluorescent lamp (about 15 Watts with an electric ballast) provides the same illumination as a 60-Watt incandescent lamp and lasts up to 10 times longer. Additionally, have excellent color rendering. b. In larger daylit spaces like gymnasiums or meeting rooms, consider ganged compact fluorescents as a practical means of addressing the need for dimmable lights. c. Consider fixtures with effective reflector design. 6. Metal Halide and High-Pressure Sodium Lamps a. Consider metal halide and high-pressure sodium lamps for exterior lighting applications. b. Use metal halide and high-pressure sodium lamps only in areas where the long warm up and restrike time after a power outage will not affect the safety of students, visitors, and staff. 7. LED Exit Lights a. Select light-emitting diode (LED) exit lights. Exit signs operate 24 hours a day, 365 days a year. LED exit signs offer energy savings between 80 kilowatt-hour/year and 330 kilowatthour/year per fixture with little maintenance. LED exit lights have a projected life ranging from 700,000 hours to more than 5 million hours and the standby battery requires replacement about every 80,000 hours. Typical fluorescent lamps will last only 15,000 hours. Lighting and Power Systems

34 8. High Efficiency Reflectors a. High-efficiency fixtures employ two main strategies to minimize the blockage or trapping of light within the fixture housing. These two strategies are high-efficiency lensed troffers and fixtures with parabolic reflectors. 9. Ballasts 1. Incorporate well-designed troffers that use the shape and finish of the inner housing to minimize inter-reflections and maximize lumens per Watt. A high-efficiency troffer with two or three lamps can produce the same illumination as a standard four-lamp fixture. 2. Selected fixtures with parabolic reflectors as an alternative means to improve optics and increase the performance of the light fixture. a. Solid state electronic ballasts are available in both rapid-start and instant-start models. The instant-start ballasts have a very high efficiency but should be avoided in applications where sensors are used. Electronic and magnetic ballasts are identical in shape, size, and external wiring, but electronic ballasts can each operate up to four lamps. b. While selecting a dimmable ballast, consider that magnetic ballasts will only dim to about 40% of full power before the flicker becomes problematic, whereas electronic ballasts may be dimmed to near zero output with no perceptible flicker. Electronic ballasts also have a higher lumen output at reduce power levels than magnetic ballasts. c. Select high-efficiency electronic ballasts because they save energy, have a low propensity to attract dust, and incorporate a minimum of hazardous materials. These also operate at a cooler temperatures. d. Select electronic ballasts because they minimize the characteristic humming from fluorescent lamps. e. Consider that conventional ballasts cycle at 60 Hertz and create a perceptible flicker, whereas electronic ballasts cycle faster, reducing eye strain. 10. Lumen Maintenance a. The output of a fluorescent lamp decreases over its rated life. The strategy used for maintained light level calculations is the initial light output of the luminaires multiplied by factors for lamp depreciation, luminaire depreciation, and room surface dirt depreciation. This will reduce the calculated output by at least 25% 30%. b. The better strategy is to measure the light output at the work surface using a light sensor in an open loop control. This will save power initially, extend the life of the lamps, and compensate for dirt on luminaires and room surfaces. It is important to establish a program of group lamp replacement because this will ensure that overall lighting levels are even and maintenance labor costs by are reduced by 88% over spot replacement. Lighting and Power Systems

35 11. Lighting Controls a. Evaluate switching versus dimming strategies. The following comparison is offered as a guide for such evaluations. Switching Dimming Inexpensive More expensive Abrupt light changes Added flexibility HID lamp restrike time Gradual level change May reduce lamp life May reduce lamp life Increases service life Burnt out lamp appearance Better used for indirect lighting Increased incandescent lamp life Reduces efficacy Check dimming range and residual power use May give color shift Square law dimming effect b. Consider switching where daylight levels are consistently high and tasks are non-critical (atriums, walkways, warehouses, etc) c. Consider dimming where daylight levels are close to target, tasks are critical and tolerance for controls is low (office areas, classrooms, etc.) d. From an energy-savings perspective, switching typically outperforms dimming if daylight levels are consistently higher than target; dimming typically outperforms switching if daylight levels are close to or less than target. e. Consider infrared, ultrasonic, or a combination of infrared and ultrasonic motion detectors in all major spaces to turn off the lights when the space is not occupied. f. In daylit spaces, consider staged or dimmable lighting controls tied to photocells located within each space and capable of reading light levels at the work surface g. Incorporate override switches for automatic daylight dimming controls only where the need to manually control lighting levels is necessary to function the space. h. Consider photocell on outdoor lights to ensure that they are off during daytime hours. Lighting and Power Systems

36 12. Power Systems An inefficient electrical distribution system in a building can result in degraded power quality, the introduction of wasteful harmonics, and line losses up to 4%. a. Evaluate the merits of a high-voltage distribution system, taking into consideration the initial cost and operational savings due to reduced line losses. Analyze the costs of delivering power at 208/120 volts versus 480/277 volts. b. Consider more efficient transformers that operate at lower temperatures c. Consider using K-rated transformers to serve non-linear equipment. d. Wherever possible, minimize long runs of wire from power distribution panels to electrical equipment. Where equipment would be likely to operate at a low voltage due to distance from the distribution panel, install a larger size wire to reduce the voltage drop. e. Consider high-efficiency motors and, where appropriate, variable frequency drives for motors. Compare motors using No. 112, Method B, developed by the Institute of Electrical and Electronic Engineers (IEEE). f. Consider fans and pumps for the highest operating efficiency at the predominant operating conditions. g. Consider energy-efficient, ENERGY STAE-rated food-service appliances; washers, dryers, and other similar equipment. h. Consider providing a grounding conductor in all raceways for the primary grounding path. i. Segregate motor, equipment and lighting loads from other more sensitive equipment loads throughout the distribution system, as is practical. j. Evaluate and specify the appropriate K-ratings for the distribution transformer where harmonics may be an issue. k. Consider problems that may arise when equipment shares receptacles on the same circuit. Determine the number of circuits, the layout of receptacles on the same circuit, and equipment that will require dedicated circuits. l. Evaluate and provide the following for computer circuits, sensitive equipment and panelboards, as required: m. Dedicated Circuits n. Isolated grounds and ground receptacles o. Transient surge suppressors p. Power conditioning q. Uninterruptible power supplies for critical loads r. Provide distribution class surge arrestors on the building power main. Lighting and Power Systems

37 s. In some cases, transient surge protection in the branch circuit panelboards might be required. The focus should be on panels with dedicated circuits that have isolated grounding provisions. t. Apply Transient Voltage Surge Suppression as needed at loads. u. Implementation of Variable Speed Drives (VSD_ should be evaluated for PQ issues and should include auto restart and manual bypass on critical loads. The inclusion on line reactors to mitigate harmonics should be evaluated on an individual drive, based on its location in the distribution system. v. Consider using Uninterruptible Power Supplies (UPS) to include online and line interactive only. Do not use standby or offline UPS on critical loads. Lighting and Power Systems

38 E. ENERGY-EFFICIENT MECHANICAL AND VENTILATION SYSTEMS 1. General a. Heating, ventilation, and air conditioning (HVAC) systems are typically responsible for 35% 50% of the energy consumed in buildings. By using the "whole-building" approach looking at how all the building's design elements work together the design team can factor in energy-saving choices that reduce heating and cooling loads and downsize the HVAC system required. b. HVAC systems have a significant effect on the health, comfort, productivity, and performance of occupants. Most of these issues are directly or indirectly linked to HVAC system design and operation, and should be maximized by improved mechanical and ventilation systems. c. Consider the HVAC design that relates all the interrelated building systems while addressing indoor air quality, energy consumption, and environmental benefit. To optimize the design to receive full benefits, the mechanical system designer and architect should address these issues early in the programming/schematic design phase and continue to assess energy consumption throughout the remaining design process. It is also important that the Owner implement appropriate levels of commissioning and routine preventative maintenance programs on mechanical systems. d. Establish mechanical equipment location and space requirements and their service clearances for commissioning proper equipment maintenance and replacement. 2. Energy Analysis a. To optimize the selection of efficient, cost-effective mechanical and ventilation systems, an energy analysis should be performed early in the process, during the schematic design phase. Several available computer programs can provide building simulations on an hourly basis to predict the energy behavior of the building s structure, air conditioning system, electrical, and central equipment plant. b. An energy analysis considers the building s key components the building walls and roof, insulation, glazing, the lighting and daylighting systems, as well as the HVAC systems and equipment. The analysis program can simultaneously assess and predict the results of choices associated with each component. For buildings in the design phase, computer models are generally useful for comparing alternatives and predicting trends. c. Energy analysis computer programs that simulate hourly performance should include a companion economic simulation to calculate energy costs based on computed energy use. This model can estimate monthly and annual energy usage and costs. Some models allow the user to input estimated capital equipment and operating costs so that the lifecycle economics of the design can be evaluated and compared. 1. Prior to starting work on the design, establish an energy budget for the project that is lower than the maximum required for the facility. 2. Develop a clear understanding of balancing initial cost versus life-cycle cost and point out the long-term advantages of investing in more energy-efficient approaches. Energy-Efficient Mechanical and Ventilation Systems

39 3. When evaluating life-cycle costs, take into account: a. the initial cost of equipment; b. the anticipated maintenance expenses; c. the projected labor costs with escalation rates; d. replacement costs; e. life expectancy of equipment. 4. Incorporate the evaluation of different fuel and energy source options over the lifecycle period. There are many alternative designs that can be used to supply air conditioning to a building. The final selection of an air conditioning system should be primarily based on the option with the least life cycle cost. Other secondary factors like space requirements, degree of control, maintenance factors, flexibility, need for individual zoning, acoustics, reliability, and off-hour operation should also be considered. 5. Identify and evaluate appropriate HVAC systems based on the building type, new or existing, and its use. 6. The most efficient systems minimize the energy required during operation by matching their air supply to the load without adding a penalty for reheat. These include: variable air volume for interior air supply with perimeter radiation for heating, interior variable air volume with perimeter constant volume, and interior variable air volume central air handling supplying air to variable air volume terminal units equipped with re-heating coils. 7. Consider variable air volume (VAV) systems with different types of terminal units, including: a. Variable air volume (VAV) with reheat coil; b. Series fan-powered VAV terminal unit; and c. Parallel fan-powered VAV terminal unit. 8. Evaluate the HVAC system and design criteria in accordance with applicable North Carolina Building codes and ASHRAE standards to: a. Provide adequate ventilation for the building occupants and building intended function; and b. Facilitate maintainability and cleanability of the HVAC system. 9. All potentially viable (at least two) HVAC systems should be identified and life cycle cost analyses performed on them. There are many options available with central plant-hydronic and central plant air delivery systems. Energy-Efficient Mechanical and Ventilation Systems

40 10. Consider energy use and operating expenditures at the outset of the design process, so energy and resource-efficient strategies can be integrated at the lowest possible cost. 11. Optimize the mechanical system as a complete entity to allow for interactions between system components. 3. Cooling Systems 12. A report should be generated containing a life cycle cost analysis of HVAC systems with justification of recommended HVAC systems at schematic and design development phases of the project. If major changes in the building design are made, revised life cycle analyses should be performed at the construction document phase of the project. 13. A report and verification of the energy analysis is required at the eleven (11) month warranty inspection. a. Consider cooling systems that match the profile and building loads. b. Evaluate various cooling equipment sizes and models to select the unit that best matches the demand requirements. To accomplish this, use an hourly computer simulation tool to generate energy consumption profiles and the incidence of coincidental peak cooling loads. Select equipment that achieves a high efficiency at the predominant load but also remains efficient over the range of operating conditions. Refrigeration Units The Coefficient of Performance (COP) of refrigeration systems is the ratio of the net heat removal by the evaporator to the total energy input to the compressor. Type A/C Package Units Chillers Centrifugal: Screw: Size (Tons) < 5 > , Condensing Air Water Air Water Water Air Minimum COP Best COP Average COP Centrifugal and Screw: < 250 > 250 Water Water Reciprocating: Absorption: Direct-Fired Single-Stage Two-Stage Indirect-Fired Single-Stage Two-Stage ,500 Air Water Water Water Water Water Source: Developed by Padia Consulting from manufacturer s literature Energy-Efficient Mechanical and Ventilation Systems

41 c. Evaluate an efficient arrangement of chiller(s), options for T and subsequently its impact, chilled water T, chilled water flow, and kw input/ton at full and part-load. Consider variable primary flow for the chiller to eliminate the use of a secondary chilled water pump and still have the advantage of a variable flow system kw Base Low Flow 0 25% Load 50% Load 75% Load Full Load This graph illustrates chilled-water-system performance at part-load. Typically, higher chilled water T with a low flow system results in lower kw input. d. Evaluate type of cooling tower, condenser water T, condenser water flow, condenser water temperature control and control of the cooling tower fan(s). e. Analyze chiller plant efficiency as a whole considering: 1. actual weather data; 2. building load characteristics/profile; 3. number of chillers with number of compressors; 4. operational hours; 5. economizer capabilities; 6. auxiliary energy draws (e.g., pumps, fans, basin heaters, etc.); and 7. energy source f. Consider the use of air side economizer and/or waterside economizer to provide free cooling. g. Use nighttime ventilation strategies to cool interior mass and flush out stale air prior to morning occupancy. This purging cycle can be effective in areas with low nighttime temperatures. Consider humidity levels inside building if this strategy is utilized. h. Use environmentally friendly refrigerant alternatives. Also, as an alternative to chlorofluorocarbons (CFC's) refrigerants, the design team should consider absorption refrigeration units which are CFC free and use water as the refrigerant and lithium bromide as the absorbent. This option can also be an economical way of cooling and heating large buildings. These compact, high efficiency units are available in models providing from 40 to 1500 tons of cooling and operate on natural gas, propane, oil, exhaust heat or steam. Because they avoid the increasingly expensive use of electricity for air conditioning, these units can cut cooling and heating costs substantially. i. Absorption cooling systems allow changing of the energy source from electricity to gas and can reduce energy costs. Direct-fired gas equipment can also be selected to provide hot water for building needs in addition to chilled water. This type of system is ideal for a solar thermal energy application. Energy-Efficient Mechanical and Ventilation Systems

42 j. Consider thermal (ice) storage in situations where peak load avoidance is critical. Thermal storage is not necessarily an energy efficiency measure, but a cost-saving technique which takes advantage of off-peak utility rate schedules where applicable. Electric utilities may have promotions for thermal storage by offering an incentive for power usage that can be displaced from peak to off-peak time. Making of ice should be considered during non-occupied hour. k. For cooling, consider the use of Dissicant Dehumidification Technology to resolve problems arising from mold and mildew. The diagram on the following page illustrates the schematic design of ice thermal storage for the Wake County Human Services Building on Swinburne Street in Raleigh, North Carolina. Ice thermal storage should be considered when electric demand changes are high and cost of electricity is significantly lower during off hours. Energy-Efficient Mechanical and Ventilation Systems

43 Energy-Efficient Mechanical and Ventilation Systems

44 4. Boilers a. When considering centralized systems, choose the most efficient heating for the particular need. b. Evaluate type and arrangement of boiler(s), heating T, hot water flow, and boiler efficiency. c. Consider condensing boilers. They are typically 10% to 15% more efficient than conventional boilers. On an average, fully-modulating and condensing boilers typically result in 20-25% higher efficiency when compared with staged or modulating non-condensing boilers. d. Consider multiple, modular boilers that are more efficient at partial load. e. Employ draft control devices that reduce off-cycle losses. f. Design water reset control that is keyed to outside air temperature. g. Incorporate burner flame controls. h. For small renovation projects, install DDC control systems to control night and weekend set-back. Energy-Efficient Mechanical and Ventilation Systems

45 5. Ventilation and Indoor Air Quality Strategies This graph illustrates the relationship between CO2 and ventilation rates, assuming adult occupants sitting or involved in office-type activity. a. Use current building codes and ASHRAE Standards, which address the criteria necessary to meet ventilation and indoor air quality requirements. The outside air requirements for proper ventilation of an occupied facility are considerable and have a substantial impact on HVAC system energy consumption and operating costs. The strategy employed to achieve proper ventilation should be carefully considered. b. Consider a dedicated ventilation system such that the quantity of air can be regulated and measured, providing a greater certainty that proper ventilation and humidity is maintained. Such a dedicated system can also improve overall energy efficiency. c. Consider the use of a heat recovery system, like an air-to-air heat exchanger, that will transfer the heat between air supplied to and air exhausted from the building. d. Separate and ventilate highly polluting spaces. Provide separate exhaust from kitchens, toilets, custodial closets, chemical storage rooms, dedicated copy rooms, and designated smoking areas with no recirculation through the HVAC system. e. Evaluate the use of an outdoor air economizer cycle that will allow up to 100% outdoor air to be introduced into the distribution system to provide space cooling. f. Locate outdoor air intakes a minimum of 7 feet vertically and 25 feet horizontally from polluted and/or overheated exhaust (e.g., cooling towers, loading docks, fume hoods, and chemical storage areas). Consider other potential sources of contaminants, such as lawn maintenance. Separate vehicle traffic and parking a minimum of 50 feet from outdoor air inlets or spaces employing natural ventilation strategies. Create landscaping buffers between high traffic areas and building intakes or natural ventilation openings. g. Locate exhaust outlets at a minimum of 10 feet above ground level and away from doors, occupied areas, and operable windows. The preferred location for exhaust outlets is at roof level projecting upward or horizontally away from outdoor intakes. Energy-Efficient Mechanical and Ventilation Systems