How much insulation is enough?

By adding insulation to your attic you can lower your annual home heating and cooling expenses by about $600. If you hire a contractor, be prepared to pay about $1,500 to lay down insulation in a typical 800-square-foot attic. In three years’ time, you will see a return on your investment. If you do the job yourself, it will cost you about half that much. Attic insulation pays for itself.

How much insulation is enough?

If you already have home insulation and want to determine if you need more in your attic, inspect the floor. If the existing attic insulation reaches just to the tops of the supporting joists, you may need added insulation. You are probably in good shape if the attic insulation goes well above the joists.

How to Insulate an Attic

There are three ways to insulate an attic:

You can use a blanket or roll-on home insulation that is sold in either 15 or 23-inch-wide rolls of batts.  This type is designed to fit within the average width of typical framing. If you already have insulation, roll out the fiberglass batts in the direction of right angles to cover the framing members.

The blanket attic insulation is the simplest to work with if this is a DIY project. Remember not to compress the material. This will render it ineffective.

Loose-fill or blown-in insulation requires a machine that shoots a stream of loose-fill cellulose over the existing attic floor framing. This is typically a job for an insulation contractor. The advantage is that loose-fill insulation does a great job of filling in small crevices and other hard-to-reach areas.

Sprayed foam polyurethane is a good choice if you plan to turn your attic into a finished room. In that case, you’ll want to insulate the roof—not the floor. Sprayed foam polyurethane molds to rafters, blocks water vapor, and has a high R-rating per inch. Expect to pay about double the per-square-foot cost of roll-on and loose-fill insulation.

Related: Attic Air Leaks: How to Find and Seal Them

How Much Attic Insulation Is Enough?

To determine how much to add, look up the recommended amount for your area, then subtract the value of your existing insulation. If you don’t know, you can figure it out using the Home Energy Saver online energy audit tool.