Published: March 3, 2016


A building enclosure, including roof, walls and windows, is designed to protect building occupants from the elements; hot and cold, rain and snow, sunlight and wind. Put another way, the building enclosure keeps the outside out, allowing for comfortable spaces to live and work. Infiltration is the uncontrolled movement of unconditioned air through a building enclosure.

The schematic below illustrates the process of infiltration in a building envelope. Infiltration increases the heating and cooling energy requirements of commercial buildings, and degrades occupant comfort.

Several research studies have measured infiltration rates of both new and old commercial buildings (Emmerich and Persily, 2005), and reported high levels of infiltration in all building vintages, climate zones, and building types. There is significant potential for improving both new and existing commercial buildings by reducing excess infiltration rates.

Infiltration is unconditioned air that enters the building from a variety of paths.

ASTM, 2012, ASTM E2813-12: Standard Practice for Building Enclosure Commissioning,

Emmerich S and Persily A, 2005, Airtightness of Commercial Buildings in the U.S. 26th AIVC Conference, Brussels, Belgium.

Lough, M, December 2012, Building Enclosure Commissioning: An Introduction, AIA Best Practices.
National Institute of Building Sciences, 2012, NIBS Guideline 3-2012: Building Enclosure Commissioning Process BECx,

Persily, A, March 1993, Envelope Design Guidelines for Federal Office Buildings: Thermal Integrity and Airtightness, NISTIR 4821.

Tratt, S, 2014, Air Sealing Existing Buildings for Energy Savings, 2014 ABAA Conference presentation,

Zhivov, A, Bailey, D, and Herron, D, U.S. Army Corps of Engineers – Air Leakage Test Protocol for Building Envelopes, This document outlines the Army Corp’s air leakage test protocol.