Residential Ventilation and Energy Characteristics

The role of ventilation in the housing stock is to provide fresh air and to dilute internally-generated pollutants in order to assure adequate indoor air quality. Energy is required to provide this ventilation service, either directly for moving the air or indirectly for conditioning the outdoor air for thermal comfort. Different kinds of ventilation systems have different energy requirements. Existing dwellings in the United States are ventilated primarily through leaks in the building shell (i.e., infiltration) rather than by mechanical ventilation systems. The purpose of this report is to ascertain, from best available data, the energy liability associated with providing the current levels of ventilation and to estimate the energy savings or penalties associated with tightening or loosening the building envelope while still providing ventilation for adequate indoor air quality. Various ASHRAE Standards (e.g., 62, 119, and 136) are used to determine acceptable ventilation levels and energy requirements. Building characteristics, energy use, and building tightness data are combined to estimate both the energy liabilities of ventilation and its dependence on building stock characteristics. The average annual ventilation energy use for a typical dwelling is about 61 GJ (roughly 50% of total space conditioning energy usage); the cost-effective savings potential is about 38 GJ. The national cost savings potential, by tightening the houses to the ASHRAE Standard 119 levels while still providing adequate ventilation through infiltration or mechanical ventilation, is $2.4 Billion. The associated total annual ventilation energy use for the residential stock is about 4.5 EJ (ExaJoules).