3.2   Air Sealing Safety

SWS Detail:2.0401.1 Air Sealing Moisture Precautions, 2.0101.1 Air Sealing Worker Safety

Air sealing reduces the exchange of fresh air in the home, and can alter the pressures within the home. Before air sealing, sur­vey the home to identify both air pollutants that may be concen­trated by air sealing efforts and open combustion appliances that may be affected by changes in house pressure.

Don’t do air sealing when there are obvious threats to the occu­pants’ health, the installers’ health, or the building’s durability that are related to air sealing. If any of the following circum­stances are present, either postpone air sealing until they’re cor­rected or correct the problems as part of the air-sealing work.

•       Measured carbon monoxide levels exceed the suggested action level. See "Carbon Monoxide (CO) Testing" on page 256.

•       Combustion zone depressurization exceeds the limits shown in “Maximum CAZ Depressurization” on page 548 during a worst-case test. See "Worst-Case CAZ Depressur­ization Test" on page 258.

•       Occupants will use unvented space heaters as a primary source of heat after weatherization is complete.

•       The air-leakage area has moisture damage, indicated by staining, mold or rot.

3.2.1   Air Sealing and Fire Containment

SWS Detail: 4.1001.5 Dense Pack Preparation, 3.1001.1 Penetrations and Chases, 3.1001.2 Chase Capping, 3.1001.3 Walls open to Attic—Balloon Framing and Double Walls, 3.1403.1 Air Seal Concrete Floor Slab Foundation: Raised, On Grade, and Below-Grade, 3.1001.6 Firewall in Unconditioned Attic, 3.1001.7 Firewall in Conditioned Attic, 3.1001.8 Preparing for and Installing Insulation Around High-Temperature Devices, Systems, and Components

Fire, flame, and smoke spread through the paths of least resis­tance. Many building assemblies harbor concealed voids or cavi­ties within walls, ceilings, and attics. During a fire, these pathways spread fire and make fire-fighting difficult.

In new buildings, the IRC requires builders to seal all shafts and hidden air leaks between living spaces and intermediate zones with fire-blocking materials.

The building codes define a fire-block as a material installed to “resist the free passage of flame through concealed spaces.” Fire-blocking materials need not be non-combustible.

We recommend rigid fire-blocking materials such as the follow­ing ones suggested in the IRC.

•       Plywood, OSB or other wood sheeting (3/4 inch thick)

•       Drywall (1/2 or 5/8 inch thick)

•       Mortar, reinforcing material, and compatible non-combus­tible caulking to air-seal masonry building assemblies.