NIST Time|NIST Home|About NIST|Contact NIST

HomeAll Years:AuthorKeywordTitle2005-2010:AuthorKeywordTitle

Workplan to Analyze the Energy Impacts of Envelope Airtightness in Office Buildings.

pdf icon Workplan to Analyze the Energy Impacts of Envelope Airtightness in Office Buildings. (2292 K)
Emmerich, S. J.; Persily, A. K.; VanBronkhorst, D. A.

NISTIR 5758; 31 p. December 1995.


Department of Energy, Washington, DC

Available from:

National Technical Information Service
Order number: PB96-154463


office buildings; air flow modeling; building energy simulation; building technology; commercial buildings; computer simulation; heating; ventilation; air conditioning; infiltration


U.S. office buildings consume approximately 1.2 EJ (1.1 Quadrillion BTUs or Quads) of energy, 0.72 EJ (0.68 Quads) of which is associated with space heating, cooling, and ventilation. These estimates, and other analyses of energy consumption in office buildings, are based on building energy analysis programs such as DOE-2. These analyses have been helpful in identifying opportunities for energy efficiency, developing building energy efficiency standards and predicting future energy consumption levels. Although these programs contain sophisticated models of heat transfer and HVAC system performance in buildings, they are acknowledged to have shortcomings in accounting for the energy associated with building airflows, particularly infiltration of outdoor air through leaks in the building envelope. These airflows, and their dependence on weather and ventilation system operation, are more complex than the models used in these programs. The simple models of infiltration, ventilation and interzone airflows that are used in these programs do not enable the analysis of the energy consumption associated with building airflow or the impact of options that may reduce this energy consumption, such as increased envelop airtightness or better control of ventilation system airflow rates. This report describes the impact of building airflows on energy consumption in multi-zone buildings and the analysis approaches that can be used to account for the energy associated with these airflows. Plans to link a multi-zone network airflow analysis program with a building energy analysis program are discussed. An initial estimate of the energy associated with infiltration in U.S. office buildings, based on a simplified analysis approach, is presented. This estimate reveals that infiltration in U.S. office buildings accounts for 0.074 EJ (0.07 Quads) of space heating energy use, which is 18% of the total heating energy use, and 0.0025 EJ (0.0024 Quads) for cooling, which is 2% of the total.