Retro-Commissioning & Commissioning Building Envelope Systems to Reduce Health Risks & Improve IAQ: What We Have Learned To Date

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1 Retro-Commissioning & Commissioning Building Envelope Systems to Reduce Health Risks & Improve IAQ: What We Have Learned To Date William A. Turner M.S., P.E. - President Steven M. Caulfield, P.E., CIH - Vice President Brian Decker, EIT - Mechanical Engineer Frederick McKnight, EIT - Chief Indoor Air Quality Engineer David Hart, NCARB - Project Architect Turner Building Science, LLC Loren Belida, AIA - Senior Vice President - Architecture The H.L. Turner Group Inc. Synopsis During , Turner Building Science, LLC had the opportunity to retro-commission and commission four moderately-sized building envelopes. These facilities included three mediumsized schools, and one medium-sized, multiple-story office facility. In the retro-commissioning situations, the diagnostic evaluations included observations of existing drawings; on-site visual observations of wall, roof, and floor/slab; actual construction during and after intrusive disassembly; infrared thermography observations; field modified ASTM moisture intrusion window system testing; ASTM concrete moisture testing; and standardized mold/fungi source testing procedures. In the new construction situation, commissioning included visual observations during the construction process, and other testing/evaluation techniques as warranted. In all of the buildings, careful evaluation of the HVAC system design and control functions, and the resulting building shell (envelope) pressures were also noted. The envelope retro-commissioning services were conducted in buildings where historically poor performance of the building envelope and possible health concerns were the drivers for the owner s decision to retro-commission the facilities. In two of the cases, the technical results determined that both mold remediation under containment and major envelope re-construction were warranted. The technical results were used to formulate major reconstruction plans for the building envelope in order to improve both long-term energy efficiency and building performance, and to reduce possible health risk within the facilities. The resulting successful reconstructions should allow the building envelope to perform well for another thirty to fifty years of service, and significantly reduce energy consumption due to envelope loss. Within this paper and during our presentation, we will summarize the testing procedures used, give examples of what was learned from the procedure, and explain how the results were used to develop a suitable corrective action plan and budget for reconstruction. In the newly constructed facility, envelope commissioning was simply used as part of the overall building HVAC Commissioning to confirm whether the owner was being delivered the design intent of the envelope design, and to develop a corrective action plan if warranted. Turner et al: Retro-Commissioning & Commissioning Building Envelope Systems to Reduce Health Risks Copyright By TBS, 2005, Materials May Be Used By Permission Only With Credits To Turner Building Science, LLC

2 INTRODUCTION Turner Building Science, LLC has enjoyed the opportunity of providing retro-commissioning and commissioning services for several buildings located in the climate of the Northeastern United States. (Ref. #1) The Northeast part of the United States can be an especially challenging location for design and construction activities, as it is considered to be cold and damp by professional literature; however, it also frequently experiences sometimes-lengthy summer conditions, very similar to a hot and humid climate. This paper and presentation will focus on various building envelope conditions we have found to be important while retro-commissioning and redesigning a failed school located in Central Massachusetts, and a new school located in Central New Hampshire. Lessons learned from both paper analysis and field performance testing commissioning activities will be presented. In the retro-commissioning case, the focus was to understand failure modes, design suitable long-term fixes, and to validate the expected performance of those fixes. In the new school, commissioning and performance acceptance testing activities were focused on the owner s goal to receive a building envelope that was likely to perform as well as intended in the climate where it is located. The ultimate goal, in both cases, was to provide a building with envelope systems that would both reduce health risks and improve Indoor Air Quality for the occupants, while ensuring longterm value for the owner. We believe that these goals are an important part of creating a sustainable building envelope. TYPES OF BUILDING ENVELOPE SYSTEM EVALUATIONS THAT CAN BE PERFORMED In the retro-commissioning or new construction situations, there are several types of building envelope paper calculations and field diagnostic evaluations that we are aware of that can be performed. These analyses can be done after the fact to determine failure modes or performance, or during design review (before construction) to predict expected building performance. Paper Calculation Reviews or Tools That We Have Found Useful: Building envelope review topics that we have currently determined to be useful activities include: Dew Point / Vapor Pressure Review: Predicting the vapor pressure relationships and location of dew point occurrences in wall, roof, or floor assemblies in occupied facilities, with significant indoor winter humidity, or significant outdoor summer humidity. Calculation tools include calculations found in American Society of Heating Refrigerating and Air Conditioning Engineers, Inc. (ASHRAE) Fundamentals publications. (Ref.# 2) Exterior Drainage Plane / Wind Barrier Review: Design drawing review for continuity and constructability of exterior drainage planes intended to keep wind driven rain (liquid water) out of the thermal envelope, and reduce the impact of liquid water / wind (infiltration) on the thermal envelope layers. 2

3 Interior Air Barrier / Vapor Barrier Review: Design drawing review for the continuity and constructability of interior air / vapor barriers designed to keep interior moisture out of the thermal envelope, and reduce the impact of interior moisture / air leakage (exfiltration) on the thermal envelope layers. Exhaust Re-entrainment Review (Micro Climate Analysis): Design drawing review and calculations, if needed, for predicting the expected impact of local point source emission sites, and exhaust locations on air intake locations (including operable windows and doors). Calculation Tools include calculations found in ASHRAE Fundamentals publications. (Ref.# 3) Thermal Performance Continuity Review: Design drawing review for predicting the expected continuity and thermal performance of a wall, roof, and below grade assemblies are based on actual conveyed construction details. This review also includes review of thermal breaks and vapor barriers in all earth contact areas. This is especially important with building envelopes that are expected to be high performance, and which include metal (conductive) structural components. Calculation tools include calculations found in ASHRAE Fundamentals publications, and commercial software. (Ref. #4) Thermal Performance Peak / Peak Occupancy Air Conditioning Impact Review: Design drawing review for predicting the expected impact of planned or sometimes unplanned occupancy periods, combined with low angle solar gain and glass (fenestration) design, on HVAC peak room cooling loads at maximum winter, low sun impact angles. Calculation Tools include calculations found in ASHRAE Fundamentals Publications, Commercial software, and our custom Advantage Displacement Ventilation Software. (Ref. #5, Ref. #6) Building Envelope Pressure Review: Design drawing review for predicting the expected overall long-term average building pressure relationship between the inside and outside of the building envelope under summer, swing season, and winter conditions. Building Envelope Air Leakage Review: Design drawing review for predicting the expected building air leakage rate and air leakage sites due to expected stack effect or planned pressure levels. (Ref. #7) Roof Ice Dam Review: Design drawing review for predicting the likely occurrence of roof snow melt from interior exfiltration or winter solar roof gain and subsequent ice damming in vented or un-vented roof assemblies. This is most applicable on roofs where microclimates and building roof designs are expected to significantly impact snow accumulation on a given Southern or Northern roof exposure. Useful Field Performance Evaluations: Performance testing (field verification) for various building envelope problems which we have most recently found to be useful include: Infrared Imaging of Buildings as Found: Determining the thermal (conductive) performance of roof and wall assemblies. There is an ASTM method for this procedure. (Ref. #8) 3

4 Infrared Imaging with Building Pressure Manipulation: Determining the air leakage sites in roof and wall assemblies. There is an ASTM method for using fan pressurization equipment to manipulate building pressures. (Ref. #9) Smoke Tracer Testing with Building Pressure Manipulation: Determining the air leakage sites in roof and wall assemblies utilizing theatrical fog with and without building pressure manipulation. There is a draft ASTM method for using this technique. (Ref. #10) Infrared Imaging and Visual Observations to Locate Moisture Infiltration/Leakage into the Thermal Envelope: Under certain defined conditions, IR Thermography, conducted indoors or outdoors with a uniformly heated interior space, has proven useful in locating currently damp wall assemblies that would be otherwise hard to find. Visual observations for signs of past water damage can also be useful. Field Determination of Water Penetration of Installed Exterior Windows, Skylights, Doors, Curtain Walls, and Wall Assemblies: Determining the actual conditions for water leakage, and utilizing intrusive disassembly to locate actual water leakage sites have proven invaluable for problem solving in existing structures. There is an ASTM method that outlines this activity. (Ref. #11) Field Determination of Exhaust Impacts on Air Intakes or Impact of Sewer Gas Leakage: Determining the observed airflow pattern of local exhausts or local point sources on air intakes under real life weather conditions. We typically utilize a tracer smoke (theatrical fog) for this evaluation. This method has also worked well for determining sanitary sewer gas vent (odor) reentrainment or internal leakage sites. Concrete Floor Moisture Emission Testing: Determining the concrete floor moisture emission rate is a common need in existing structures since the advent of water based floor adhesives. There are draft ASTM testing techniques and other standardized testing methods for this determination. (Ref. #12, Ref. #13) Building Envelope Pressure Monitoring: In some buildings, it is important to know the actual peak and long-term average pressures that the HVAC system imposes on the building envelope during normal operation, (summer, winter, swing season) versus what may have been intended or designed. Some Results From Applying These Retro-Commissioning or Performance Acceptance Testing Techniques Case Study A: Existing Central Massachusetts School Historically poor performance of the building envelope and occupant reported health concerns prompted the owners to retro-commission the facility. In this case, the actual trigger for the initial activity was a major roof collapse during a winter snow load event, which flooded and 4

5 closed the school. Additionally, flooding from sprinkler line breakage during the roof collapse and historic severe ice dams warranted a physical investigation to determine specific locations where mold growth had occurred on wallboard, such that it could be removed throughout the facility under proper containment. Retro-Commissioning Paper Study Evaluations and Performance Testing Lead to the Following Decisions: Dew Point / Vapor Pressure Review: Calculation of the vapor pressure relationships and location of dew point occurrence in the existing wall lead to a decision to add 2 inches of Extruded Polystyrene (EPS) insulation to the exterior of the six inch metal stud and fiberglass batt wall. This significantly improved the thermal envelope, moved the dew point into the EPS, and allowed the extra boiler capacity to be used to heat more outside air to bring the outdoor air supply to the currently recommended 15 CFM per person for classroom areas. Exterior Drainage Plane / Wind Barrier Review: Observed rotting wood near windows, failed window leakage tests, and intrusive disassembly revealed a failed exterior drainage plane system. The exterior drainage plane and wind barrier were re-designed. Interior Air Barrier / Vapor Barrier Review: Design drawing review for continuity of the interior air / vapor barriers and intrusive disassembly revealed that the system, as it existed, could remain in place, once mold contaminated gypsum wallboard was replaced. Exhaust Re-entrainment Review (Micro Climate Analysis) and Field Testing: Theatrical smoke testing revealed re-entrainment of several sewer gas vents, and as a result, the stacks were relocated. Boiler stack re-entrainment calculations lead to the extension of the boiler stack to move the exhaust plume above the rooftop HVAC air intakes. Infrared Thermal Performance Evaluation: Gross air leakage into the attic, and then to the outdoors, lead to a solution to move the thermal envelope to the pitched roof plane, and a drastic reduction of envelope exfiltration resulted. Building Envelope Pressure Testing: Fan pressure testing confirmed gross air leakage and observed reasons for the reported major ice dams. This also supported a re-design of the roofing system. Roof Ice Dam Review: Ice damming was reported to be a major problem and also supported the redesign of the roof insulation system. Infrared Imaging to Locate Moisture Infiltration/Leakage into the Thermal Envelope: This analysis confirmed gross rainwater entry into two wall systems and a soffit area. This also supported re-design of the roof. Field Determination of Water Penetration of Installed Exterior Windows, Skylights, Doors, Curtain Walls, and Wall Assemblies: This evaluation and intrusive disassembly lead to the redesign of the wall / windows flashing system, and replacement of all North exposure windows. 5

6 Concrete Floor Moisture Emission Testing: Results of this testing in the non-vented mode, followed by intrusive disassembly at representative locations, lead to a decision to provide perimeter footer drainage, a gully system to allow roof water to move away from the building, and a decision to strip and seal the concrete floor. Performance Acceptance Testing Prior to Re-occupancy was Conducted: Results of infrared imaging confirmed the delivery of a high-performance building envelope. HVAC commissioning activities resulted in further adjustments to the HVAC controls, and the development of a preventative maintenance plan. Follow Up: The occurrence of a small ice dam on a South exposure during very cold weather from solar gain and snow melt lead to minor modifications to the south facing roof valley. The technical results of the above evaluations were utilized to determine that major envelope redesign and re-construction was warranted, and to formulate major reconstruction plans for the building envelope. Goals of the envelope upgrade included both improved long-term energy efficiency/building performance, and reduced possible future health risk within the facility. Exterior metal stud walls were upgraded with EPS to R-30, and the attic insulation system was moved to the roofline and was changed to a true R-20, with a vented Polyiso system. The outdoor air supply to the classroom areas was doubled to meet current ASHRAE Std. 62 guidelines, and low sidewall returns were added. By utilizing energy recovery ventilation, a 100% outside air system was installed without increasing the boiler capacity. Flooring/site concrete moisture problems dictated the need for improved site drainage and the need to add a negative side moisture retarder floor sealing system prior to the use of water based mastics. The resulting successful major envelope upgrade, during roof and wall re-construction, should allow the building envelope to perform well for another 30 to 50 years of service, and significantly reduce energy consumption due to reduced envelope losses and the use of energy recovery ventilation. The above was accomplished during an intense four-month reconstruction period. Case Study B: New School Construction, Central New Hampshire: During the design process by The H.L. Turner Group, Inc., Turner Building Science, LLC provided a review of all design documents. Items considered in cooperation with the Architect of Record included the following: Dew Point / Vapor Pressure Review / Thermal Performance Review: Predicting the vapor pressure relationships and location of dew point occurrences in walls, roof, and floor assemblies lead to a design decision to use rigid foam insulation in all locations to improve overall building moisture and thermal performance. 6

7 Exterior Drainage Plane / Wind Barrier Review: Design review for continuity and constructability of exterior drainage planes lead to a decision to use essentially redundant drainage planes and wind barriers. Both tape joints on EPS, and a building paper, were employed under a masonry composition clapboard exterior with a small air space behind it. Interior Air Barrier / Vapor Barrier Review: Design drawing review for the continuity and constructability of interior air / vapor barriers design confirmed a continuous, rigid air barrier inside the entire structure. Exhaust Re-entrainment Review (Micro Climate Analysis): Design drawing review lead to the decision of where to locate boiler stacks for optimum separation and dilution from rooftop air intakes. Thermal Performance Peak / Peak Occupancy Air Conditioning Impact Review: Review for predicting the expected impact of planned low angle solar gain and glass (fenestration) design on HVAC peak room cooling loads lead to minimization of glass areas for improved daylighting performance, and minimum impact on the cooling burden for the Advantage Displacement Ventilation system. This system uses 100% outside air with enthalpy recovery and displacement air supply in all classrooms and assembly areas. It produces comfortable classroom conditions calculated to be at one-half the operating cost per CFM of outside air, compared to a conventional AC approach. Building Envelope Pressure Review: Design review for predicting the expected overall longterm average building pressure relationship between the inside and outside of the building envelope lead to the decision to focus on a slight overpressure, or neutral pressure design. Exhaust air supply is not greater than makeup air. Building Envelope Air Leakage Review: Design review for the envelope revealed a very tight envelope design which resulted in a reduction in the heating system capacity of the boilers. Roof Ice Dam Review: Design review revealed a very low likelihood of ice dams. Solar gain and snow melt experienced for one period in the winter did produce a small ice dam during very cold weather on a south exposure. Performance acceptance testing was conducted for the HVAC system controls and other building systems as follows: Infrared Imaging of Buildings as Constructed: Infrared testing confirmed no major air exfiltration or thermal losses. Determining at what point in the construction process to make this test remains a construction scheduling challenge. Field Determination of Exhaust Impacts on Air Intakes or Impact of Sewer Gas Leakage: Performance acceptance testing of the sanitary sewer vents revealed one vent impacting a rooftop air intake under certain prevailing winds, and two internal leakage sites resulting from poor workmanship. Determining when during construction to make this test remains a construction scheduling challenge. 7

8 SOME CONCLUSIONS: We have found that building envelope commissioning activities can reveal very valuable information that might otherwise not be observable or technically quantified. Quantification of the situation through standardized testing can result in acceptable conclusions for all parties involved in an often-complicated construction process. For example, Architects and Engineers of Record, Construction Managers, Contractors, Owners Representatives, etc. can then focus on effective decision making and problem resolution given objective technical evaluations. From these technical results, engineering and architectural designs, and their performance, can most often be predicted and field validated if needed. All of these commissioning efforts are intended to produce a high performance building that will meet the owner s and designer s intent, and with proper maintenance and operation, continue to do so. Commissioning activities that identify problem areas that could impact the occupant s health or the value of the owner s building can reduce the risk to all parties involved. The ultimate goal of building envelope commissioning activities is the delivery of a building with envelope systems that offer both reduced health risks and improved indoor air quality to the occupants, thus providing long-term, affordable value for the owner. We believe that these goals are an important part of creating a building envelope that will be sustainable, and would welcome feedback on any of the concepts we have presented. 8

9 REFERENCES CITED: 1. ASHRAE (1997), Fundamentals Handbook, Chapter 26, pp , American Society of Refrigerating and Air Conditioning Engineers, Atlanta, Georgia 2. ASHRAE (1997), Fundamentals Handbook, Chapter 22, pp , American Society of Refrigerating and Air Conditioning Engineers, Atlanta, Georgia 3. ASHRAE (1997), Fundamentals Handbook, Chapter 15, pp , American Society of Refrigerating and Air Conditioning Engineers, Atlanta, Georgia 4. ASHRAE (1997), Fundamentals Handbook, Chapter 24 & 23, pp , American Society of Refrigerating and Air Conditioning Engineers, Atlanta, Georgia 5. ASHRAE (1997), 1997, Fundamentals Handbook Chapter 28 & 29, pp , American Society of Refrigerating and Air Conditioning Engineers, Atlanta, Georgia 6. The H.L. Turner Inc. (2005), Proprietary Information, Advantage Displacement Ventilation, software, The H.L.Turner Group Inc., 27 Locke Rd. Concord, NH ASHRAE (1997), Fundamentals Handbook, Chapter 25, pp , American Society of Refrigerating and Air Conditioning Engineers, Atlanta, Georgia 8. ASTM (Reapproved 1997), Standard Designation: C Standard Practice for Thermgraphic Inspection of Insulation Installations in Envelope Cavities of Frame Buildings, Committee C-16.30, American Society for Testing and Materials, West Conshohocken, PA. 9. ASTM (1999) Standard Designation: E , Standard Test Method for Determining Air Leakage Rate by Fan Pressurization, American Society for Testing and Materials, West Conshohocken, PA. 10. Verbal Communication, (2005), Mr. Henri Fennel, Foam-Tech, P.O. Box 87 - North Thetford, VT ASTM (2000) Standard Designation: E , Standard Test Method for Field Determination of Water Penetration of Installed Exterior windows, Skylights, Doors, and Curtain Walls, by Uniform Cyclic Static Pressure Difference, American Society for Testing and Materials, West Conshohocken, PA. 12. ASTM (2002) Standard Designation: F , Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes, American Society for Testing and Materials, West Conshohocken, PA. 10

10 13. ASTM (2003) Standard Designation: F , Standard Test Method for Measuring Vapor Emission Rate of Concrete Subflooring Using Anhydrous Calcium Chloride, American Society for Testing and Materials, West Conshohocken, PA. 11