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Adding Insulation to an Existing Home

May 23, 2013 - 1:44pm

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Adding insulation in an existing home saves money and improves comfort. | Photo courtesy of Dennis Schroeder, NREL.

Adding insulation in an existing home saves money and improves comfort. | Photo courtesy of Dennis Schroeder, NREL.

Unless your home was specially constructed for energy efficiency, you can probably reduce your energy bills by adding more insulation. Many older homes have less insulation than homes built today, but even adding insulation to a newer home can pay for itself within a few years.

To determine whether you should add insulation, you first need to find out how much insulation you already have in your home and where it is. A qualified home energy auditor will include an insulation check as a routine part of a whole-house energy assessment. An energy assessment, also known as a home energy audit, will also help identify areas of your home that are in need of air sealing. (Before you insulate, you should make sure that your home is properly air sealed.)

If you don't want an energy assessment, you need to find out the following for yourself:

  • Where your home is, isn't, and/or should be insulated.
  • What type of insulation you have.
  • The R-value and the thickness or depth (inches) of the insulation you have.

If you live in a newer house, you can probably get this information from the builder. If you live in an older house, you'll have to inspect the insulation.

Inspecting and Evaluating Your Insulation

Check the attic, walls, and floors adjacent to an unheated space, like a garage or basement. The structural elements are usually exposed in these areas, which makes it easy to see what type of insulation you have and to measure its depth or thickness (inches).

Inspect the exterior walls by using an electrical outlet:

1. Turn off the power to the outlet.

2. Remove the outlet cover and shine a flashlight into the crack around the outlet box. You should be able to see if there is insulation in the wall and possibly how thick it is.

3. Pull out a small amount of insulation if needed to help determine the type of insulation.

4. Check outlets on all floors as well as old and new parts of your house. Just because you find insulation in one wall doesn't mean that it's everywhere in the house.

  • Inspect and measure the thickness (inches) of any insulation in unfinished basement ceilings and walls, or above crawlspaces. If the crawlspace isn't ventilated, it may have insulation in the perimeter wall. If your house is relatively new, it may have insulation outside the basement or foundation walls. If so, the insulation in these spaces won't be visible. The builder or the original homeowner might be able to tell you if exterior insulation was used.
  • Once you've determined the type of insulation you have in these areas and its thickness (inches), see the U.S. Department of Energy's online Insulation fact sheet to determine the R-values of insulation previously installed in your home.

Determining Recommended R-Values

When you find out the R-values of your insulation either from an energy assessment, the home builder, or your own inspection, you can then use the U.S. Department of Energy's Zip Code Insulation Calculator to determine how much insulation you should add and where you should add it for maximum energy efficiency.

Estimating Costs and Payback

The Zip Code Insulation Calculator provides insulation cost estimates and a rate of return on your investment. Also see our information on estimating the payback period of additional insulation.

Deciding What Type of Insulation to Add

If you decide to add insulation to your home, review our information on the types of insulation available to help you decide what type to use and where to insulate.

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