House Airtightness Testing And When Not To Air Seal

House Airtightness Testing And When Not To Air Seal

House airtightness testing was made possible by the development of the blower door. The blower door measures a home’s leakage rate at the standard pressure of 50 pascals.

This leakage measurement is used to compare homes with one another and set air-leakage standards. The blower door also allows the technician to test parts of the home’s air barrier to locate air leaks. Testing air barriers with a blower door isn’t always necessary. Sometimes air leaks are obvious. Other times the leaks are hidden, and the technician wants to obtain clues about their location without crawling needlessly into dark and dirty places. This article outlines the basics of blower door testing along with some techniques for gathering clues about the location of air leaks.

Air Sealing
Air Sealing and House Envelope


When not to air seal:

Perform no air sealing when there is an obvious threat to the occupants health, the installers health, the building’s durability, or to the effectiveness of the air sealing materials.

The following circumstances must be corrected before or during air-sealing work, or else air-sealing shouldn’t be performed:
1. The building is scheduled for demolition or major rehabilitation and the materials would likely be removed.
2. Moisture has caused structural damage, rot, mold or mildew growth.
3. Fire hazards place building’s life and occupant safety in jeopardy.
4. Carbon monoxide levels exceed suggested action levels.
5. Combustion zones pressure exceed -5 pascals when the air handler is running.
6. Chimney drafts of combustion appliances do not meet minimum standards.
7. An unvented space heater is used after air-sealing work.
8. Infestations, vermin, or sanitary issues are present.
9. The building is already at or below the Building Tightness Limit and no mechanical ventilation exists or is planned.


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