What this covers
Wall insulation fills the stud bays of exterior walls. When the walls are open during a remodel or a rebuild, the installer fits batts, spray foam or blown-in material between the studs and adds a vapor retarder where the code calls for one. When the walls are closed, the installer removes a row of siding or works from inside, drills small holes into each bay, and dense-packs cellulose or another loose fill until the cavity is full. Blocking, wiring and window headers are found first so no bay is missed. The holes are plugged and the siding or wall is patched.
When to call
- Exterior walls that feel cold to the touch in winter.
- An older house with little or no insulation in the walls.
- Walls opened after a water loss that need insulation before drywall.
What to expect
- AssessThe installer checks what is in the walls, often with a small inspection hole or an infrared camera.
- AccessOpen walls are prepared, or a row of siding is removed and holes drilled into each bay.
- InsulateEach bay is filled with batts, foam or dense-packed loose fill.
- PatchHoles are plugged and the siding or interior wall is put back for finishing.
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 walls be insulated without tearing them open?
Yes. Dense-pack insulation is blown into each stud bay through small holes drilled from outside or inside, and the holes are plugged afterward.
Does wall insulation need a vapor retarder?
It depends on the climate and the wall assembly. The installer follows the local code, which sets where a vapor retarder goes and which kind.
What about old knob-and-tube wiring?
Insulation should not be packed around knob-and-tube wiring that is still live. An electrician evaluates it first, and the wiring is usually replaced before the walls are insulated.
Related: Blown-in insulation · Batt insulation · Water damage restoration · 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.