Roof Air Barrier

An air barrier is part of the building envelope that limits uncontrolled air movement through the roof assembly. In practice this means sealing gaps at penetrations, top plates, and transitions so warm, moist indoor air does not flow into the attic. It works together with insulation and ventilation—not as a replacement for them.

When warm air leaks into a cold attic, it can melt snow on the roof. The meltwater refreezes at the eaves and forms ice dams, which can back water under shingles. Reducing air leakage keeps the attic colder so snow stays frozen and reduces the conditions that cause ice dams. Proper ventilation is still essential.

The best time to address air sealing is often during a roof replacement or major repair, when we have access to the deck and penetrations. We can seal around pipes, vents, and gaps before the new underlayment and roofing go on. For existing roofs, targeted sealing at accessible points still helps.

No. Insulation resists heat flow; an air barrier limits air movement. You need both. In Utah, we also focus on ventilation so the attic can dry and stay at a consistent temperature. The combination of insulation, air sealing, and ventilation gives the best performance and helps avoid moisture and ice dam issues.