How to Insulate Your Attic and Save Money Year-round

Adding attic insulation is one of the easiest ways to reduce your energy bills. Here’s how to know whether you need more.

| July 17, 2007

As summer winds down, probably the last thing on your mind is climbing into your attic and putting up more insulation.

But consider this: A well-insulated attic could slash your air conditioning bills throughout these warmer months in addition to reducing heating costs once winter rolls around.

“Adding additional cellulose insulation to an attic is often one of the most cost-effective strategies for improving the energy performance of a home,” says Alex Wilson, author of Your Green Home and president of BuildingGreen, a company that helps businesses improve the environmental performance of their buildings. “Not only will the added insulation reduce heating and air conditioning bills, but it will also improve comfort by helping to seal air leaks.”

Here are steps to get started on this money-saving project that’s relatively easy to do yourself.

1: Grab a yardstick or tape measure and make the ascent into your attic. Determine the R-value (the resistance to heat flow) of your current insulation by measuring its thickness in inches and multiplying that number by the R-value per inch for your type of insulation:

Fiberglass blanket or batt 3.2
High-density fiberglass blanket or batts 3.8
Loose-fill fiberglass 2.5
Loose-fill rock wool 2.8
Loose-fill cellulose 3.5
Perlite or vermiculite 2.7
Expanded polystyrene board 3.8
Extruded polystyrene board 4.8
Polyisocyanurate board, unfaced 5.9
Polyisocyanurate board, foil-faced 7.0
Spray polyurethane foam 5.9

For example, if you have loose-fill cellulose attic insulation that measures 10 inches thick, you have an R-value of about 35.

5/17/2014 3:48:15 PM

A few years ago I found that my blanket insulation was sliding off the attic hatch (scuttle hole) as I lowered it into place. I set up a video camera in my attic and found that every time I tried to lower the attic hatch the insulation got stuck up in attic - leaving my hatch uninsulated. This was because insulation is wider than the opening so there is no way for it to fall into place without help. If you try to glue or staple the attic insulation to the hatch it won't work because the insulation just pulls apart when it catches on the surrounding insulation, framing or joist webs. I came up with a product that solves this problem and it's now available. Please go to and look at the video. It's an easy, inexpensive and effective way to insulate your attic hatch.

7/24/2009 9:46:26 AM

Is there a conspiracy to misstate the R-value of cellulose insulation? Almost all cellulose has a rating of R-3.8 per inch. It's R-3.8 per inch whether it is "loose fill" in attics or packed tightly in walls. If painting your roof actually cools your living area down then you clearly are in need of cellulose insulation in your attic and probably walls too.

9/24/2008 9:33:53 AM

I have recently had insulation blown into the floor joists in my attic. I am wondering ig it would be a good idea to put batting the between the joists in the roof as well, or would this trap too much heat and moisture? I only have two end gables for vents, not raised roof venting like in the newer homes. Thanks!

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