Saving Energy: Insulating Your Home

Insulation is rated by its R-value, which measures its thermal resistance or how well it holds back heat. The higher the R-value, the better.

Bare concrete walls are about R-1, while attic insulation in newly-built Midwestern homes usually measures about R-44.

R-value is proportional to the insulation's thickness, but it also depends on the type of material and its density. The more air pockets an insulating product has, the higher the R-value.

For example, R-38 attic insulation may be 12 inches of fiberglass batts, 10 inches of rock wool loose-fill or seven inches of expanding foam.

Don’t miss:

Types of
Insulation

Type of insulation:

Cellulose

Fiberglass

Rock wool

R-value per inch:

3.2-3.8

2.2-2.7

3.0-3.3

Inches needed for R-38:

10-12

14-17

11.5-3

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Are you an Alliant Energy customer?

If you’re an Alliant Energy heating customer in Iowa or Minnesota, you can earn cash back when you upgrade your attic insulation.

Looking for an energy-smart insulation contractor or retailer?

Try Alliant Energy’s online Dealer Locator to find experts in your area.

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Brochures and fact sheets:

PowerHouse: Insulating Your Home
By Alliant Energy [PDF format]

Attic Insulation Fact Sheet
By the U.S. Department of Energy [PDF format]

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Learn more:

Insulation
Fact sheet from the U.S. Department of Energy

Simply Insulate
Advice from the North American Insulation Manufacturers Association

Insulation FAQs
Expert answers from the National Insulation Association