What this covers
Air sealing closes the gaps that let air move between the house and the attic, the crawlspace and the outdoors. The biggest leaks are usually hidden: open wall tops, plumbing and wiring holes, flue chases, recessed lights, the attic hatch and the rim joist. The installer pulls back insulation, seals small gaps with caulk or foam, covers large openings with rigid board, uses fire-rated materials and metal flashing around flues and chimneys, and weatherstrips doors and hatches. A blower door test before and after shows how much the leakage changed. Air sealing is usually done before new attic insulation goes down.
When to call
- Drafts around outlets, baseboards, doors or the attic hatch.
- Dust streaks on carpet edges or insulation where air has been moving.
- Ice dams or frost on the underside of the roof deck in winter.
- An energy audit that showed high air leakage.
What to expect
- TestA blower door test measures leakage and helps locate the main gaps.
- FindThe installer works through the attic, basement and rim joists marking each bypass.
- SealGaps are sealed with caulk, foam, board or fire-rated material as each one needs.
- RetestA second test shows the change, and combustion appliances are checked for safe venting.
Get a certified company
Look up a certified company by ZIP code. Every company's license, insurance and trades are verified before it is listed, and placement is never paid.
Questions people ask
Can a house be sealed too tight?
A house still needs fresh air, and tighter houses may need mechanical ventilation. The installer checks that fuel-burning appliances vent properly after sealing and tells you if ventilation should be added.
Why seal before insulating?
Insulation slows heat but does not stop air. Sealing first closes the leaks, and once new insulation is on top, the gaps are much harder to reach.
What is a top plate?
The horizontal framing at the top of a wall. In the attic, the gaps where wires and pipes pass through it are common leak points.
Related: Home energy audits · Attic insulation · Ductwork installation and repair · All insulation and energy
This page describes what the service involves. The company you hire sets the scope, the schedule and the price, and your contract is with that company. We verify credentials and collect reviews from real jobs. We do not guarantee any company's workmanship. Safety steps are general guidance. When in doubt, leave the home and call 911.