American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

Infiltration in ’s Residential Ventilation Standards
 N LO-09-085

Annotation

INTRODUCTION

Infiltration, adventitious or incidental air leakage through building envelopes, is a common phenomenon that affects both indoor air quality and building energy consumption. Infiltration can contribute significantly to the overall heating or cooling load of a building, but the magnitude of the effect depends on a host of factors, including environmental conditions, building design and operation, and construction quality. Typically infiltration accounts for one-third to one-half of the space conditioning load of a home.

In addition to increasing the conditioning load of a building, infiltration can bring unwanted constituents into the building or into the building envelope and cause building failures. For example, infiltration of hot, humid air in an air conditioned building in the summer (or exfiltration of indoor air in a heated building in the winter) can cause condensation in the building envelope leading to potential structural failure and mold growth. For these reasons reducing infiltration is desirable.

Infiltration, however, serves a vital purpose in most existing homes: it is the dominant mechanism for providing ventilation. The purpose of ventilation is to provide fresh (or at least outdoor) air for comfort and to ensure healthy indoor air quality by diluting contaminants. Historically, people ventilate buildings to provide source control for both combustion products and objectionable odors (Sherman 2004). Currently, a wide range of ventilation technologies is available to provide ventilation in dwellings including both mechanical systems and more sustainable technologies. Most of the existing housing stock in the U.S. uses infiltration combined with window opening to provide ventilation. Sometimes this results in overventilation with subsequent energy loss or under-ventilation and poor indoor air quality.