indoor-outdoor air leakage of apartments and commercial buildings

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3.0 Glossary ACH Air Changes per Hour Air Changes Per Hour Airtightness Building Shell Building Envelope Building Footprint Exfiltration Flow Coefficient HVACsystem Infiltration Leakage Leakage Parameter Leakiness Pascal Volume of building, divided by the flow rate (volume per hour) of air leaving the building. Generic term for resistance to indoor-outdoor airflow that a building provides. See Leakiness. Exterior walls and roof of a building. All parts of a building through which air can pass to the outdoors. See Building Shell. The total area enclosed by a building's foundation. Normally equal to the building's roof area. Phenomenon of air leaving a building through pathways other than a ventilation system. The term C in the equation Q = C· A . /..,pn (See Equation 6.1). This equation relates the Air Flow Rate (Q) to the leakiness of the building (parameterized by C), the Area (A) of the building's shell, and the indoor-outdoor pressure difference (AP). Heating, Ventilating, and Air Conditioning System. Mechanical systems that provide air, including air from the outdoors. Phenomenon of air entering a building through pathways other than a ventilation system. Air flow across the building shell. Same as infiltration. Same as Flow Coefficient Generic term for the lack of resistance to indoor-outdoor airflow that a building provides. See Airtightness. Standard unit of pressure. 1 Newton per square meter. I! 8
I, 4.0 Executive Summary Indoor-outdoor air-exchange rates affect energy costs because conditioned (heated or cooled) air that exits a building must be replaced by air from the outdoors. This air must then be brought to the indoor temperature through use of air conditioning or heating. Excess air exchange leads to unnecessary energy costs and a waste of resources. Additionally, air exchange removes pollutants that were generated indoors and admits pollutants that were generated outdoors, so the air exchange rate is a key parameter in controlling indoor air quality. Most pollutant concentrations are much higher indoors than outdoors, so insufficient air exchange leads to inadequate indoor air quality and thus discomfort and detrimental health effects. Indoor-outdoor air exchange takes place in two ways: through intentional ventilation and through undesired infiltration or "leakage." In this report we discuss what is known about leakage into apartment buildings and nonresidential buildings (which we will refer to as "commercial buildings," even though some of them are schools or other non-commercial uses). Much of our analysis concerns the leakage parameter, which quantifies amount of outdoor air that enters a building when there is a given pressure difference between indoors and outdoors. This is essentially a measure of the airtightness or leakiness of a building's shell. In contrast, a measurement of a building's air exchange rate, which is the rate at which air is entering the building at a particular time, depends not just on properties of the building but also on factors such as the wind speed and direction, operation of the mechanical ventilation system (if any), and the indoor-outdoor temperature difference. We consider both air exchange rate data and leakiness data in this report, but the emphasis is on the leakage parameter. We reviewed the published literature to determine the current state of knowledge about air infiltration in commercial buildings and multifamily-residential buildings. Previous work in these areas has generally considered either small subsets of the available building data, or simple univariate summary statistics describing larger datasets. For apartment data these approaches are probably the best that can be done, due to the paucity of data, but for commercial buildings the available data, though sparse, allow more detailed analysis, which we have performed. In contrast to the situation for single-family homes, where there is an available database of more than 70,000 measurements, the published database of leakage parameter measurements for apartments and commercial buildings is very small. We found data on fewer than 300 commercial buildings in the North America and Europe, and approximately 150 apartment buildings in North America, including unpublished data from 75 commercial buildings. Only a few buildings are from California, and it is unknown whether there is a large difference in leakiness between buildings in California and buildings elsewhere. Due to (1) sparseness of data, and (2) the fact that buildings were not chosen to be statistically representative of typical buildings, the available data allow only very crude estimates of the statistical distribution of air exchange rates or building leakage area parameters, and of the relationship between leakage parameters and factors such as building size, construction materials, etc. They are, nevertheless, the best available source of information 9
Page 1: LBNL-60682 INDOOR-OUTDOOR AIR LEAKA
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Page 13 and 14: I I I J Additionally, air exchange
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Page 25 and 26: variables listed here, but there ar
Page 30 and 31: o 5000 10000 15000 20000 Footprint
Page 34 and 35: Lagus and Grot (1995) measured the
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Page 46 and 47: experience with making measurements
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Page 50 and 51: EIA, 2003. "Commercial Buildings En
Page 52 and 53: Reardon, J.T., AK. Kim, and CY. Sha
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surrounding the building. Wind-pres
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BUGS, for Bayes Using Gibbs Samplin
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Coefficient Std. Country Name Mean
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Data Coefficient Country Building T
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STU DY_ID 2 SOURCE CY Shaw, "Air ti
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STUDY_ID 6 SOURCE Leif I. Lundin, "
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STUDYJD SOURCE JB Cummings, CR With
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STUDY_ID 14 SOURCE PJ Jones, G Powe
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APPENDIX IV: APARTMENT BUILDING DAT
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Title Air Leakage and Fan Pressuriz
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Airtightness Survey of Row Houses i
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Valuing Air Bariers Duncan Hill Hom
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Balanced Fan Depressurization Metho
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DISCLAIMER This document was prepar
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indoor-outdoor air leakage of apartments and commercial buildings

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