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Floor plan of case study residence with existing ducts. Upper level on top.

Floor plan of case study residence with existing ducts. Upper level on top.

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Article
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This case study focusing on a residence in northern California was undertaken as a demonstration of the potential of a systems approach to HVAC retrofits. The systems approach means that other retrofits that can affect the HVAC system are also considered. For example, added building envelope insulation reduces building loads so that smaller capacit...

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... roof was constructed with colored ceramic tiles on a sloped plywood deck, over a naturally ventilated and unconditioned attic, with fiberglass insulation (R-26) between the 2 by 8 joists on 16" centers. A floor plan of the test residence with existing ducts is shown in Figure 1 and exterior views are displayed in Figure 2. ...
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... "Smart Vent" (fresh air ventilation controller model SV10) temperature- controlled economizer in attic (through the roof -the economizer roof-vent is shown in Figure 10). The economizer monitors indoor and outdoor temperatures. ...
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... retrofit duct schematic for the supply side of the systems is shown in Figure 11. 8. Closed existing return because it was leaky and no possible way to seal it. Installed a larger upstairs return in new location (upstairs hallway ceiling) to assist in reducing temperature stratification. ...
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... metal ducts in the attic with new R-4 flexible ducts because the contractor thought they were undersized. Initially the contractor hung the flex-ducts from the attic ceiling with smooth bends as shown in Figure 12. However, we planned to add insulation over the ducts and wanted them installed directly on the attic floor plane. ...
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... we planned to add insulation over the ducts and wanted them installed directly on the attic floor plane. The contractor then placed the new ducts on the floor per our request in Figure 13, but unfortunately did not take the time to lay the ducts with smooth bends as shown in Figure 14. ...
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... we planned to add insulation over the ducts and wanted them installed directly on the attic floor plane. The contractor then placed the new ducts on the floor per our request in Figure 13, but unfortunately did not take the time to lay the ducts with smooth bends as shown in Figure 14. ...
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... Added R-8 fiberglass wrap to R-4 insulated attic flex ducts for a total insulating value of about R-12 as shown in the right hand photo in Figure 15. 11. Added at least 4" (R-12) of blown-in fiberglass insulation to R-4 attic flex ducts for a total insulating value of R-16 as in Figure 15. ...
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... Added at least 4" (R-12) of blown-in fiberglass insulation to R-4 attic flex ducts for a total insulating value of R-16 as in Figure 15. ...
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... we did not meet this specification (14% return leakage, 9% supply leakage) due to excessive leakage at the economizer outdoor air damper. Figure 16 shows the duct sealing using foam of the downstairs return. The aerosol method internally seals leaky ducts by injecting an aerosol sealant into the duct system as shown in Figure 17. ...
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... 16 shows the duct sealing using foam of the downstairs return. The aerosol method internally seals leaky ducts by injecting an aerosol sealant into the duct system as shown in Figure 17. ...
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... Added 5" (R-17 R3.4/inch) of blown-in fiberglass insulation to R-37 attic floor plane for a total insulating value of R-54 as shown in Figure 15. ...
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... supply and return air data that were monitored include plenum takeoffs for upstairs and downstairs drybulb temperature and downstairs relative humidity (Figure 16). These data are shown in Figure B.3. ...
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... zonal and attic air data that were monitored include downstairs thermostat temperature, attic temperature and attic relative humidity (Photo B.7). These data are shown in Figure B.1(e). The downstairs thermostat temperature was set at 25.5°C (78°F) and normally was between 23 and 26°C. ...

Citations

... Requires knowledge of duct areas, high uncertainty [96,105,160] Pressure matching with powered, calibrated fan operating as flow hood Typically greater accuracy than capture hood [97,105,106,183,184] Continuous flow measurements Flow meters installed directly into HVAC system (e.g. venturi meters, flow nozzles, orifice meters, rotameters) Invasive, requires HVAC access, data logger, and power [96,190] Duct pressure correlations with spot flow measurements Simple and cost-effective, requires data logger and power [102,[107][108][109] Outdoor air (OA) fraction in mechanical HVAC systems Tracer (e.g., temperature, CO 2 , or SF 6 ) in RA, SA, and OA Accuracy issues at low concentration changes, high costs for accurate sensors, requires injection, data logger, and power [110,191] Zone tracer testing (e.g., CO 2 , SF 6 ) coupled with room volume Costly, labor intensive, requires assumptions for mixing [111][112][113][114][115]192] Building automation system (BAS) readings, including economizer settings Often low accuracy, sensor reliability, requires access to facility data, typically only present in large buildings [193] Air change rates (ACH) Active tracer gas (e.g., CO 2 or SF 6 ) ...
Article
Full-text available
Recent studies have greatly increased our knowledge of microbial ecology of the indoor environments in which we live and work. However, the number of studies collecting robust, long-term data using standardized methods to characterize important building characteristics, indoor environmental conditions, and human occupancy – collectively referred to as “built environment data” – remain limited. Insufficiently described built environment data can limit our ability to compare microbial ecology results from one indoor environment to another or to use the results to assess how best to control indoor microbial communities. This work first reviews recent literature on microbial community characterization in indoor environments (primarily those that utilized molecular methods), paying particular attention to the level of assessment of influential built environment characteristics and the specific methods and procedures that were used to collect those data. Based on those observations, we then describe a large suite of indoor environmental and building design and operational parameters that can be measured using standardized methods to inform experimental design in future studies of the microbial ecology of the built environment. This work builds upon the recently developed MIxS-BE package that identifies high-level minimal built environment metadata to collect in microbial ecology studies, primarily by providing more justification, detail, and context for these important parameters and others from the perspective of engineers and building scientists. It is our intent to provide microbial ecologists with knowledge of many of the tools available for built environment data collection, as well as some of the constraints and considerations for these tools, which may improve our ability to design indoor microbial ecology studies that can better inform building design and operation.