Insulation installation: what to know

What the job involves, what changes the price, and what to ask a pro.

What insulation installation is

Insulation installation adds batts, blown-in or rigid insulation in attics, walls or crawl spaces to slow heat loss. The work usually includes air sealing, because gaps let heated air escape even when the insulation is thick, and it keeps vents and recessed fixtures clear so the house stays safe.

Signs you need it

  • The attic floor has little or no insulation, or the insulation is flattened, wet or missing in places.
  • Rooms over the garage, above the porch or next to an unheated space are much colder than the rest of the house.
  • The heating and cooling run constantly, or the house feels drafty near outlets, windows and the attic hatch.
  • The crawl space or basement floor is cold and damp, and the floor above feels cold.
  • You are finishing a basement or converting a space, and the walls need insulation before the drywall goes up.
  • Ice dams or frost form on the roof edge in winter, which can point to heat escaping into the attic.

What the pro does

  • Inspect the attic, wall cavities or crawl space, and check for air leaks at the top plates, the can lights, the chimney and the attic hatch.
  • Seal the air leaks with caulk, foam or sheet material before insulation goes in, and block the gaps around pipes and wires.
  • Keep the soffit vents clear with baffles at the eaves, so the insulation does not block the air path to the roof vents.
  • Install batts, blown-in material or rigid board to the depth the house needs, keeping a gap around any recessed fixture that is not rated to be covered.
  • Add insulation at the attic hatch and the knee walls, and insulate the rim joists or the crawl space walls if they are part of the job.
  • Check the finished work for coverage and depth, and confirm the vents and the fixtures are clear.

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Area to be insulated, measured by attic floor, wall cavity or crawl space square footage.
  • Insulation type, such as fiberglass batts, blown-in cellulose, blown-in fiberglass or rigid board, each with different labor.
  • Target depth, which depends on the climate and the R-value the home needs.
  • Amount of air sealing needed before insulation goes in.
  • Access to the space, such as a tight crawl space, a steeply pitched attic or a finished wall.
  • Whether the home has older loose-fill material that must be tested or removed before new insulation goes in.
  • Whether the attic has baffles, vents or wiring that must be cleared or rerouted first.

What a written quote should spell out

  • The area covered and the insulation type for each space.
  • The target depth or R-value for each area.
  • Air sealing materials and the locations sealed.
  • Baffles, vent clearing and any fixture protection, listed separately.
  • Removal or testing of any older loose-fill insulation, if needed.
  • Warranty terms for the materials and the workmanship.

Questions to ask before you hire

  • What R-value are you installing, and how did you choose it for my climate?
  • Will you air seal before the insulation goes in, and where will the sealing be?
  • Will you install baffles at the eaves so the soffit vents stay clear?
  • How will you handle the recessed lights and the chimney clearance?
  • If there is older loose-fill insulation, will you test it before disturbing it?
  • Will you show me the depth of the insulation after the install?
  • Who pulls a permit if one is needed, and what warranty comes with the work?

Red flags

  • The pro covers recessed light fixtures that are not rated for insulation contact.
  • The pro blocks the soffit vents with insulation and leaves no air path to the roof vents.
  • The pro skips the air sealing and fills the attic with insulation over open gaps.
  • The pro says the old attic insulation has to go without checking it for asbestos.

What you can do yourself

You can clear the attic floor, add weatherstripping and a cover to the attic hatch, and note any wet or damaged insulation for the pro to see. Do not pull out or disturb older loose-fill insulation until it has been tested, and do not bury recessed fixtures, the chimney or the flue. Air sealing at penetrations, the insulation install and any work near wiring belong to a licensed contractor.

Licenses and permits

Insulation installation is often done by licensed contractors, and some areas require a license or certification for insulation work. Check with your state or local licensing agency for the requirements that apply to your project.

Insulation installation questions

Can I put insulation over old knob-and-tube wiring?

Not without an electrician checking it first. Insulation can trap heat around old wiring and cause it to overheat. An electrician should evaluate the wiring before insulation goes over it.

Why do I need air sealing before insulation?

Gaps at the top plates, the attic hatch and the pipe penetrations let warm air move through the insulation. Sealing them first lets the insulation do its job.

How do I know how much insulation I need?

The right depth depends on the climate and the material. A technician measures the existing insulation and recommends a target R-value for the space.

Could my attic insulation contain asbestos?

Some older loose-fill insulation can contain asbestos. Have it tested before disturbing it, and use a licensed abatement contractor if the test is positive.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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