S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 1 0 HU B B S • 9 9 HIGH-PERFORMANCE BUILDING ENCLOSURES CAUSE CONDENSATION AND INDOOR AIR QUALITY PROBLEMS: THE NEED FOR INTEGRATED DESIGN AND IMPROVED INVESTIGATION PROTOCOLS BRIAN HUBBS, PENG RDH BUILDING ENGINEERING LIMITED 224 West 8th Avenue, Vancouver, BC, Canada V5Y 1N5 Phone: 604-873-1181 • E-mail: bch@rdhbe.com COAUTHORS: ROBERT ORLOWSKI GRAHAM FINCH, EIT 1 0 0 • HU B B S S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 1 0 ABSTRACT Multifamily buildings in the Lower Mainland of British Columbia and the U.S. Pacific Northwest have come under increasing scrutiny due to the high incidence of water ingress and resulting deterioration of exterior wall assemblies. Current trends in architectural and HVAC design in combination with changes in building enclosure design to improve water penetration control and energy efficiency often result in increased potential for condensation related moisture problems. This paper examines these changes through a series of case studies showcasing typical problems that can occur. Innovative monitoring and modeling techniques are also presented that shed new light on the multidisciplinary cause of the problem. Recommendations are provided for integrated architectural and HVAC design to accommodate the more airtight and insulated wall and window assemblies used on buildings today, as well as guidance to occupants and building managers to minimize risk of condensation- related moisture problems in exterior wall assemblies. SPEAKER BRIAN HUBBS, PENG — RDH BUILDING ENGINEERING LIMITED Brian Hubbs is a principal and senior building science specialist with RDH Building Engineering in Vancouver, BC. He has 19 years of experience working exclusively as a consulting engineer focused on building enclosure issues in all climate zones across North America. This work has included the design of new building enclosures as well as forensic investigation, rehabilitation, maintenance, and litigation support on existing buildings. Brian has also been a key team member on the many landmark building-science research and policy projects focused on the West Coast climate zone. S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 1 0 HU B B S • 1 0 1 ABSTRACT Multifamily buildings in the Lower Mainland of British Columbia, Canada, and the United States’ Pacific Northwest have come under increasing scrutiny due to the high incidence of water ingress and resulting deterioration of exterior wall assemblies. The fact that the majority of these moisture problems have been related to water ingress has overshadowed other moisture-related building enclosure issues. With the recent widespread adoption of rainscreen technology, improved detailing, and better quality control, water ingress issues have been reduced significantly, raising the profile of other moisture issues such as condensation. Current trends in architectural and heating, ventilation, and air conditioning (HVAC) design, in combination with changes in building enclosure design to improve water penetration control and energy efficiency, often result in increased potential for condensation-related moisture problems. This paper examines these changes through a series of case studies showcasing typical problems that can occur. Innovative monitoring and modeling techniques are also presented that shed new light on the multidisciplinary cause of the problem. Recommendations for integrated architectural and HVAC design to accommodate the more airtight and insulated wall and window assemblies used on buildings today, as well as guidance to occupants and building managers to minimize risk of condensation- related moisture problems in exterior wall assemblies is provided. A new test methodology for the investigation and monitoring of condensation problems is also presented. INTRODUCTION The potential for condensation to occur on the interior surfaces of walls and windows, in simple terms is related to several factors: • Exterior environmental conditions • Thermal resistance of layers within the wall assembly • Thermal characteristics of the window assembly • Position of the window within the wall assembly, as well as details of the installation • Location and distribution of heat within the suite • Interior source generation of moisture • Ventilation of interior air to manage interior relative humidity conditions These basic influences on condensation potential have been understood for many years. However, recent trends within multiunit residential construction have created a combination of factors that can lead to increased potential for condensation and accumulation of moisture. Moisture accumulation can result in damaged materials and mold growth on surfaces. One recent trend that affects building performance that stems from the current housing boom and corresponding increase in housing prices is the market for very small living spaces. For architects, this results in a challenge to design usable living spaces while minimizing footprint area. Often with limited floor space, the only available location to place large furniture such as beds and couches is adjacent to exterior walls. In addition, the trend towards maximizing the amount of glazing area and ceiling height discourages the use of drop ceilings to enclose perimeter mechanical ductwork to supply heated dry air to the building perimeter and adds to the need for opaque window coverings for privacy. These three factors reduce the amount of interior heat getting to the perimeter and increase the potential for condensation. Trends toward the use of high-performance rainscreen wall and window assemblies, especially those with exterior insulation over a waterproof air/vapor/moisture barrier membrane, result in much more effective airtightness compared to traditional wall and window assemblies. This increased airtightness results in a corresponding reduction in natural ventilation across the building enclosure. The lack of natural ventilation must be considered when designing the building HVAC system, especially in colder climates where windows are not likely to be opened during periods of cold weather. In addition, the increased use of exposed concrete walls incorporating eyebrows and concrete curbs increases the risk of condensation on colder surfaces by creating thermal bridges. Attachment to these exposed concrete elements at connections, in particular at the window-to-wall interface, also increases the risk of condensation. In an effort to reduce costs or, in some cases, increase “Leadership in Energy and Environmental Design” (LEED) points, some designers are moving away from traditional electric or steam-based perimeter heating systems and moving to more centralized heating forms such as gas fireplaces, radiant flooring, and core-based radiant or forced-air systems. This can result in a reduction in perimeter heating and thus, colder surfaces, leading to increased risk of condensation and associated moisture problems. Measured relative humidity (RH) levels within suites have been found to be higher in newer buildings than is traditionally assumed in HVAC and building envelope design. Our design assumptions and, consequently, our designs need to be reevaluated. It is also clear that the way occupants use their suites and maintain HVAC equipment can have a profound impact on condensation performance. In particular, the typical occupant’s lack of basic knowledge regarding the factors influencing condensation potential can result in increased condensation problems. This issue represents a very complicated interaction of architectural design, HVAC design, and maintenance/occupant use that together determine success of an exte- HIGH-PERFORMANCE BUILDING ENCLOSURES CAUSE CONDENSATION AND INDOOR AIR QUALITY PROBLEMS: THE NEED FOR INTEGRATED DESIGN AND IMPROVED INVESTIGATION PROTOCOLS rior wall assembly with respect to condensation control. It is not simply a matter of making assumptions regarding internal and external environmental conditions and undertaking a basic vapor-diffusion analysis of the wall assembly. Before we can develop solutions, a better understanding of these complex interactions is required. To understand the multifaceted cause of the problems requires improved investigation techniques that consider all the variables. Using a series of investigative case studies, we have summarized the concerns surrounding these issues and have developed integrated design considerations for all disciplines as well as the end users. NEW INVESTIGATION PROTOCOL When performing an investigation on a building that is experiencing condensation and/or interior air quality problems, it is important to develop an investigation methodology that includes all of the critical variables. Without complete data, interpretation of the results can easily lead to erroneous conclusions and incomplete recommendations. The classic approach to investigating a building with condensation problems is to install a few temperature and RH sensors in a problematic suite for a given period when condensation occurs within the unit. Typically, one sensor is used in each bedroom, with one in the main living area. Data from the sensors are cross-referenced with information from the occupants on their activities that affect the moisture levels. This helps to explain the various trends and anomalies found in the data. The information provided by this type of sensor data is very limited. When analyzing the data, only theories can be derived as to the causes of moisture changes because each source is not monitored individually. The full impact of the HVAC system on the problem is often not even considered. An advanced monitoring protocol was developed for a recently constructed residential high-rise complex in the Pacific Northwest that had been experiencing condensation problems during periods of cold weather since construction. The building was constructed of concrete and incorporated high-performance rainscreen window and wall assemblies. The owners of the building wanted to understand the cause of the condensation issues and specifically to determine why condensation was prevalent on some suites but not on others that had the same layout and construction. In addition to the normal temperature and RH data loggers, the following information was collected to assist in investigation: • Logged operation and flow rates of all HVAC equipment (including all exhaust fans, furnace fan, and clothes dryer) • Measured airflow rates at supply vents and at windows during furnace fan operation • Measured hallway supply air under all combinations of HVAC equipment operation • Logged suite CO2 levels • Calculated building enclosure air leakage rates from test data • Logged window frame and glazing temperatures at corner and center of sills, indicating when condensation was occurring and allowing a comparison of the effects of furnace supply air A complete layout and sensor description for a sample control/condensation suite pair is shown in Figure 1. The use of individual sensors for each source location allows for clear understanding of the source of the moisture and what countermeasures are used to deal with any resulting increase in RH. For example, the master bedroom received three sensors in the following locations: en suite bathroom, bedroom, and window surface. Correlating the data from these three sensors will clearly show if the occupants cause condensation or if other sources of moisture (such as a shower) contribute. With sensors also linked to the exhaust fans, the effectiveness and the extent of use of each fan could also be determined. With this monitoring protocol, a clear picture as to the exact conditions that led to condensation within the suite can be concluded from the data. A sample of the results is included. Figure 1 — Data logger and sensor setup (control and condensation suite). Figure 2 — Effect of furnace operation on window surface temperatures. 1 0 2 • HU B B S S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 1 0 HVAC FURNACE SUPPLY FAN EFFECT ON WINDOW TEMPERATURE During the analysis of the furnace-heated supply air wash to the windows, it was observed that the heat-supply vents are quite far from the windows, and the resulting flow rate of heated air wash is low and even nonexistent in many areas. This HVAC layout is already much more sensitive to condensation than traditional radiators or forced air vents at the perimeter and will result in much colder perimeter window temperatures. However, the problem was exacerbated in one suite pair by the use of a setback thermostat. Figure 2 shows a typical evening during periods of cold exterior temperature. In the control suite with no condensation, the furnace operates every 15 minutes, keeping the window temperatures around 65ºF. In the suite with condensation the window temperature steadily declines during periods where the furnace is turned off. This typically occurs at night when exterior temperatures are at their lowest. The consequence is window temperatures around 58ºF that result in condensation. One of the condensation suites’ occupants did not operate the furnace during the entire monitoring period resulting in extremely cold perimeter surface temperatures. EXHAUST FAN USE VS. SUITE DEW POINT In an optimal situation, exhaust fans would operate during moisture-generating activities and remain on until the moisture level in the room returned to its original value. In general, we found that all occupants were not consistently and properly utilizing their exhaust fans during highhumidity- generating activities. Often, exhaust fans were not utilized during showers, and if they were, it was only for the duration of the shower. In many cases, it took up to ten hours for the increased humidity from a single shower to be dissipated when exhaust fans were either not used or turned off immediately after a shower. (Refer to Figure 3.) IMPACT OF SUPPLY AIR QUANTITY AND QUALITY ON CONDENSATION The HVAC design for the building included a hallway pressurization system supplying conditioned fresh air to the suites by means of positive-pressure delivery under the entry doors. The only other method of providing fresh air to the suites is through operable windows that are not used during periods of cold weather and through backflow of exhaust vents under high wind pressures. In general, we observed that the supply air volume was lower and the relative humidity higher on the condensation suites in comparison with the control suites (Table 1). This lack of supply air is also reflected in the CO2 measurements that show considerably higher CO2 levels in suites with lower ventilation rates and higher levels of condensation, as shown in Figure 4. Figure 3 – Effect of shower on Suite RH and condensation without exhaust fan operation. Table 1 — Supply airflow rates. S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 1 0 HU B B S • 1 0 3 Air-flow measurements had no increase when fans were activated; the hallway pressurization was not working. ASHRAE recommendations based on suite area (accounts for 5-6 occupants). ASHRAE recommendations at 15 cfm per person for actual occupant loads. N6011 N301 Baseline 24 0 Master bathroom 55 8 Guest bathroom 53 11 Common bathroom 55 14 Kitchen level 1 55 11 Kitchen level 2 55 16 Kitchen level 3 59 29 Dryer w/ booster fan 55 14 ASHRAE recommended (based on suite size = 0.3 ACH) 82 82 % of ASHRAE recommended @ baseline 29% 0% % of ASHRAE recommended w/continuous master bath fan 67% 10% ASHRAE recommended (based on # of occupants, 15 cfm/person) 30 30 % of ASHRAE recommended @ baseline 79% 0% % of ASHRAE recommended w/continuous master bath fan 183% 27% 1Control suite Airflow IMPACT OF ENCLOSURE AIR LEAKAGE As part of the quality assurance testing of new building envelope assemblies—the American Standard Test Method (ASTM) E783, Standard Test Method for Field Measurement of Air Leakage Through Installed Exterior Windows and Doors— results were known for the wall and glazing assembly used on this project.1 The major envelope assemblies consisted of sliding balcony doors, floor-to-ceiling window-wall, and exterior insulated rainscreen metal panels. The results of this air leakage testing revealed that overall air leakage rates across the building envelope assembly were on the order of 0.09 L/(s m2) @75 Pa, which is within the recommended level outlined by the building code2 [Max 0.10 L/(s m2) @75 Pa]. The measured air leakage rate @75 Pa was converted to an equivalent leakage area (ELA75) using Bernoulli’s equation: Q = CA[(2/p)DP]1/2 (Q = flow rate, C = contraction coefficient, A = area, p = air density, and DP = pressure differential) with the following assumptions: C = 0.6, p =1.20, suite wall area = 80m2 Based on these assumptions, the ELA75 was found to be 11.4 cm2. Utilizing ELA75 and a DP of 4 Pa for the average measured pressure across the enclosure, the equivalent air leakage rate of 3.6 cfm was estimated for the entire exterior wall area of the unit tested. Table 5 of ASHRAE’s Fundamentals Handbook3 and Standard 62 suggests that a two-occupant unit should have a total ventilation rate greater than 30 cfm. With the building enclosure only capable of providing on the order of 10% of the recommended ventilation air for the suite with all windows closed, it is clear that modern high-performance building envelope enclosures should not be relied upon to provide a significant portion of the required ventilation for the unit. FIELD SURVEY OF PERFORMANCE OF HVAC SYSTEMS A survey of buildings was undertaken as part of the development of an HVAC guideline for multiunit residential buildings in the U.S. Pacific Northwest (Portland and Seattle areas).4 The purpose of this survey was to examine the actual in-service performance of HVAC systems a few years after c o n s t r u c t i o n . Information was gathered through visual observations, measurements of pressure differentials and airflow, as well as through discussions with on-site maintenance personnel and occupants. A summary of performance issues and observations follows. Fieldwork was performed only on calm days in May 2004 to minimize wind effects and stack effect, respectively. HEATING • In several instances, furniture was located in front of cadet heaters, lowering their effectiveness and/or creating a fire risk. See Figure 5. • In many instances, the electric cadets are located towards the unit interior rather than at or near an exterior wall. Also, interiorly located heat sources are often situated directly beneath thermostats. In some suites, the occupants reported feeling cold even when the heaters were used. Since heat was not being provided at the exterior walls, the relatively cold walls reduce occupant thermal comfort and increase the likelihood of condensation-related issues at the exterior walls and windows. See Figure 5. • In some suites, the occupants do not use the electric heating systems, as they are perceived to be expensive. Occupants also complain that the cadet heaters (electric fan coils) are noisy. At some buildings, plug-in style, oil-filled radiators are used in lieu of the electric baseboard or cadet heaters. See Figure 6. Figure 4 – Correlation of effect of CO2 levels on condensation. Figure 5 — Electric cadet wall heater located behind couch, away from exterior wall, and directly below the thermostat, leading to poor temperature control within the room. 1 0 4 • HU B B S S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 1 0 VENTILATION • The airflow at many bath fans was measured with a flowmeter. Some exhaust fans designed for humidity control operate continuously. These were found in poor operating condition, due to a lack of being maintained. In other locations, the fan was ineffective, due to an insufficient gap under the doorsill, which suffocated the fan. • In corridor buildings, many suites were positively pressurized relative to the corridor. Of the units that were negatively pressurized, most were 1 to 5 Pa negative relative to the corridor. One suite was 25 Pa negative relative to the corridor. • Also in corridor buildings, the supply airflow rate varied between floors of the same building. Supply air seemed insufficient in some cases to balance the sum of the continuous exhaust of the suites at that particular floor. • In many suites with continuous exhaust fans, significant lint has built up. • Some suites are provided with recalculating fans in lieu of exhausting vents. • There is inadequate ducting and booster fan used for clothes dryers. MAKEUP AIR • There is little to no gap beneath hallway doors to allow makeup air to flow to units (supply from corridor). There is also little gap at the base of bathroom doors, suffocating continuous bath fans. (The suite layout is such that bathroom doors remain closed most of the time. • Closures are installed at the base of hallway doors to stop drafts and odors from transferring from the hall under the door, cutting off the “fresh” air supply. See Figure 7. • The trickle vents in windows are often closed. • In some corridor buildings, stairwell doors are propped open, weakening the hallway pressure needed to supply fresh air to suites and disrupting mechanical system balancing. See Figure 8. • The hallway pressurization system causes inherent draft under entry doors. • There are complaints of odors from suite occupants in many buildings. • Manual-operating point-source exhaust fans are not used in many kitchens and baths. • Fans are disconnected if or when they become noisy rather than replacing or maintaining them. S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 1 0 HU B B S • 1 0 5 Figure 6 — Use of oil-filled radiators in same room as shown in Figure 5. Figure 7 — Undercut door intentionally blocked to resist drafts and control odors from hallway into suite. Figure 8 — Stairwell doors propped open, frustrating attempts to control airflow within building. Figure 9 — Cover to close exhaust grill. • Exhaust grills are fitted with covers by occupants to shut off flow because of the perception of heat loss from the exhaust systems. See Figure 9. • Exhaust ducts are terminated within attic spaces vs. being vented. • Heavy curtains at some exterior walls insulate the walls from heated air. See Figure 11. • Insufficient makeup air to utility rooms affects clothes dryer performance, reducing capacity to exhaust moist air. The field survey clearly illustrated that a combination of architectural, HVAC, and occupant factors act together to cause HVAC systems to not function as intended. The case studies that follow illustrate some examples in more detail where this dysfunction has led to condensation and moisture- related damage. IMPACT OF ARCHITECTURAL SPACE LAYOUT Si gni f i cant levels of mold and deterioration were observed within a vinylclad townhouse complex in Washington State.5 The damage occurred along the base of the walls, both at the exterior sheathing and on the interior surface of the interior gypsum sheathing. The investigation of the cause of the moisture problems identified issues related to exterior water penetration as the cause of deterioration of the sheathing. However, the high levels of mold and deterioration on the interior gypsum board (Figure 12) could not be explained by exterior moisture sources alone. In many cases, all of the visible mold was located on the interior of the polyethylene vapor retarder, while insulation and framing to the exterior of the polyethylene was observed to be in good condition (Figure 13). The investigation revealed the following issues: • Electric cadet heaters and thermostat controls were located at a significant distance from the exterior walls and were often not directed at the exterior walls (Figure 14). • The interior space layout dictated that many of the obvious locations for large furniture, such as beds and couches, were adjacent to exterior walls. The location of large furniture in these areas had the dual effect of adding insulation to the interior of the wall and blocking heat flow from the cadet heaters (Figures 12 and 14). Figure 10 — Exhaust duct terminated in attic space. Figure 11 — Curtains prevent air from circulating at exterior wall and window/wall. Conditioned air is being directed to the outside walls from an interior location almost 7m away. Figure 12 — Mold on interior surface of exterior wall in bedroom. Figure 13 — Insulation and studs in good condition on exterior of vapor barrier. 1 0 6 • HU B B S S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 1 0 • Units were constructed over an unheated parking garage, and the interior floor consisted of a structural concrete slab covered with polystyrene insulation, gypcrete, and carpet. The detail at the base of the exterior walls incorporated a perimeter concrete curb that was attached to the suspended structural slab, creating a thermal bridge through the insulation in the sandwich slab (Figure 15). • Humidity in many of the units was higher than expected, and clothing and other personal effects were found piled up against the exterior walls in a number of units. A simulation of the base-of-wall detail was performed using Therm 5.26 to better understand the contribution of the thermal bridging to the condensation and mold problem. The model used an exterior temperature of 0ºC (32ºF) and an interior temperature of 20ºC (60ºF). At this temperature and interior relative humidity of 50%, the dew point of the air is 9ºC (48ºF). The simulation in Figure 15 models the wall interface without interior furniture. The coldest interior temperature is 12.5ºC (54.5ºF), indicating that the risk of condensation would be quite low under the modeled conditions. When the same detail was modeled with a sofa on the interior of the wall in Figure 16, the results showed surface temperatures of 6.7ºC (44ºF), which is significantly below the dew point of the modeled conditions. The temperature region between 6.7ºC and 9ºC (44ºF and 48ºF), the dew point, (shown on Figure 16) is approximately the same location where interior mold was observed on the walls during the investigation. The results of the investigation indicate that the interior condensation and mold sources on this building were a result of a combination of HVAC design, interior space planning, architectural detailing, and occupant lifestyle. Figure 14 — Location/orientation of cadet heater, furniture, and resultant mold. Figure 15 — Temperature isotherm at base of wall. Figure 16 — Temperature isotherm at base of wall with sofa adjacent to interior surface. S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 1 0 HU B B S • 1 0 7 RECOMMENDATIONS The subsequent sections provide recommendations for architectural design, HVAC design, and instructions that need to be communicated to the building occupants and/or managers to help them better understand the factors that influence condensation control. It is important to note that any one of these items is not likely to be critical by itself. There generally need to be several contributing factors to create a condensation problem. As a result, each of these recommendations must be viewed in the overall building context. Concessions can be made without necessarily compromising condensation control. ARCHITECTURAL DESIGN RECOMMENDATIONS There are a variety of architecturally related items that can influence condensation potential: • The suites should be compartmentalized with an airtight perimeter maintained between the suite and the corridor and between adjacent suites. This recommendation addresses many of the airflow control issues that were identified in the field survey. • Space layout should be designed to encourage locating large pieces of furniture away from exterior walls and windows. • Poorly ventilated spaces such as closets should not be located on outside walls. • Windows should be located toward the interior portion of wall assemblies to encourage “washing” of the window with interior heated air. This maintains warmer temperatures at the surface of the window assembly. This window placement is also better from a water-penetration-control perspective, since the windows are somewhat protected when recessed. • Walls should be designed and constructed with a continuous insulating layer located somewhere within the assembly to minimize thermal bridging and maintain warmer interior surface temperatures. • Details should be designed and constructed to avoid thermal bridging such as continuous metal sill pans or anchors. • Dryers should be closer to exterior walls to provide shorter exhaust length. HVAC DESIGN RECOMMENDATIONS The majority of multiunit residential buildings use heating systems that do not require ducts. Although they have higher initial costs, ducted systems do have some advantages, since they permit a wider variety of fuel sources, easier addition of cooling, and often better delivery of fresh air and conditioned air throughout the suite. We have assumed that nonducted systems are used. The recommendations for both heating and ventilation reflect this assumption. A primary goal of ventilation is to provide good indoor air quality, which includes comfortable interior humidity levels. However, what constitutes good indoor air quality is not well defined, nor do we customarily measure it. It is assumed that by providing sufficient ventilation, good indoor air quality will be maintained. The recommendations for ventilation also reflect ASHRAE Standard 62.2, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings,7 which requires whole-house ventilation, local exhaust, and source control. Note that some of the recommendations are directly related to factors that may affect the intended function and thus condensation potential, while other recommendations are directed at managing owner/ occupant impact or intervention. HEATING • Locate heating at the exterior walls or so that heat is directed to and reaches the exterior walls. For this purpose, baseboard heating is preferable to cadet heaters. This is particularly important when designing small living spaces, since wall space for shelving and storage is at a premium. Heaters that are located on opaque wall areas will reduce this space and will likely be modified or covered over by some occupants in order to meet their space needs. • Locate thermal controls on a zoned basis usually in each room and located away from the exterior walls and heaters. • Use quiet systems to discourage occupants from disabling them. Baseboards may be preferable to cadets for this reason. • Use systems that require minimal maintenance since occupants are likely neither to do the maintenance nor to notify the owner or manager that it is required. • Provide the owner or manager with comprehensive maintenance and renewal recommendations for the heating components. VENTILATION • Meet ventilation requirements on an individual suite basis. This effectively means that each suite is treated as an independent dwelling unit from an HVAC perspective. • Use low-noise source exhaust fans (<1.5 sonnes) to encourage proper use and discourage occupant tampering. • Use constant, low-volume, wholehouse fans to provide basic air exchange for suites. • Provide fresh air to each suite. Locate/detail inlets so that they are not readily blocked by occupants. Provide adequate makeup air to run all exhaust fans and dryers effectively. • Provide the owner/manager with comprehensive maintenance and renewal recommendations for the heating components. • Take steps to minimize occupant control over source fans. (Use humidistat controls, connect to light switch so that fan is operational whenever light is on, or set to run automatically for periods of time each day.) Figure 17 provides a conceptual illustration of the recommendations for an arbitrary suite in a multiunit residential building. OCCUPANTS / BUILDING MANAGER Given the limited understanding that occupants can be expected to have regarding the interaction of factors to create condensation problems, there is a need to reinforce good operational procedures on an annual basis through educational initiatives (flyers delivered to each suite, short presentations at owner meetings). In addition, there is a need for building managers to follow the maintenance and renewals recommendations provided by the design team and to visit each suite, particularly during the winter months, to confirm acceptable condensation performance. The following is a checklist of operational items that owners and building managers will need to address from time to time: 1 0 8 • HU B B S S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 1 0 • Locate furniture so heating sources are not blocked. • Open drapes/blinds daily to allow warmer air to reach perimeter walls and windows. • Clean exhaust grilles on source fans (kitchen and bathroom) and dryers. • Use kitchen exhaust fans when cooking. • Use bathroom exhaust fans when using the bathroom – especially during a shower. • Notify the manager of problems with fans, controls, or condensation. REFERENCES 1. ASTM, (1993), E783-93, Standard Test Method for Field Measurement of Air Leakage Through Installed Exterior Windows and Doors, American Society for Testing and Materials, Volume: 04.11. 2. ASHRAE, (2001), ASHRAE Handbook – Fundamentals, Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 3. “Multi-Unit Residential HVAC System Guidelines,” 2005, Report prepared by RDH Building Sciences S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 1 0 HU B B S • 1 0 9 Figure 17 — Conceptual HVAC strategy for multiunit residential building that facilitates effective control of interior environmental conditions as well as temperatures at exterior walls. Inc. for Walsh Construction Co. 4. Investigative study performed by RDH Building Science Inc., 2004 5. THERM 5.2, Lawrence Berkeley National Laboratory (LBNL). 6. ASHRAE Standard 62.2, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings, Atlanta: American Society of Heating, Refrigerating and Air- Conditioning Engineers, Inc. 7. B. Hubbs and M. Hircock, “Building Envelope Performance Monitoring,” Proceedings Ninth Canadian Conference on Building Science and Technology, 2003, and Ongoing monitoring and data analysis for the 5-year monitoring project performed by RDH Building engineering for the Homeowner Protection Office, BC Housing, and the Canadian Mortgage and Housing Corporation. 8. National Building Code of Canada, 1995. FOOTNOTES 1. ASTM E783-93, Standard Test Method for Field Measurement of Air Leakage Through Installed Exterior Windows and Doors, American Society for Testing and Materials, Volume: 04.11, 1993. 2. National Building Code of Canada, 1995. 3. ASHRAE Handbook Fundamentals, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta, GA, 2001. 4. Multi-Unit Residential HVAC System Guidelines, report prepared by RDH Building Sciences Inc. for Walsh Construction Co., 2005. 5. Investigative study performed by RDH Building Science Inc., 2004. 6. THERM 5.2, Lawrence Berkeley National Laboratory (LBNL). 7. ASHRAE Standard 62.2, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings, Atlanta: American Society of Heating, Refrigerating and Air- Conditioning Engineers, Inc. 1 1 0 • HU B B S S Y M P O S I U M O N B U I L D I N G E N V E L O P E T E C H N O L O G Y • NO V E M B E R 2 0 1 0
