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



Steven J. Emmerich, Andrew K. Persily


US. 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 oillce 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 infWration, ventilation and interzone airflows that are used in these programs do not enable the analysis of the energy consumption wsociated with building airflow or the impact of options that may reduce this energy consumption, such as increased envelope 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 inilltration in US. office buildings, based on a simplified analysis approach, is presented.
NIST Interagency/Internal Report (NISTIR) - 5758
Report Number


airflow modeling, building energy simulation, building technology, commercial buildings, computer simulation, HVAC systems, ifilltration, ventilation


Emmerich, S. and Persily, A. (1995), A Workplan to Analyze the Energy Impacts of Envelope Airtightness in Office Buildings, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed May 22, 2024)


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Created December 1, 1995, Updated March 20, 2018