How Much Attic Insulation Do You Need?
By: Danny Lipford
Having enough insulation in your attic is one of the best ways to save energy on both heating and cooling your home.
How well a particular insulation works is expressed by the R-value, which ranges from 2.0 to 8.0 per inch of insulation.
The higher the R-value, the better job the insulation does at preventing the transfer of heat. Fiberglass and cellulose insulation have R-values of 2.9 to 3.8 per inch while sprayed foam insulation can go as high as 8.0 per inch.
According to the U.S. Department of Energy, it’s recommended that attics have an R-38 to R-49, or about 12” to 15” of fiberglass or cellulose insulation.
Use unfaced insulation when adding more insulation to an attic that already has some insulation, laying the rolls or batts at right angles to the floor joists.
If your attic doesn’t have any insulation, used faced insulation, placing it in the space between the joists with the paper side facing down toward the heated livings space.
When installing insulation, wear:
- Dust mask or respirator
- Long pants
- Long sleeved shirt
- Protective gloves
When installing fiberglass insulation, it’s also a good idea to sprinkle baby powder on any exposed skin to reduce irritation from the glass fibers.
Watch this video to find out more.
- Insulation R-Value (article)
- Getting Adequate Attic Insulation (article)
- How to Install Fiberglass Insulation in Your Attic (video)
Danny Lipford: Before you go out and buy any insulation for your attic, get an idea of how much you have in the attic now. First of all if you go into the attic, and you can see your ceiling joists, I can already tell you, you don’t have enough. Just measure what you have. Here I have about four inches, which is probably only going to relate to around an R-5, not enough by any means. And I want to shoot for about an R-35. So, I have some R-30 which is about nine inches of insulation. And I’m going to roll this out over the existing.
Now, a few things you need to know when you’re buying insulation to add to an existing attic. Make sure you don’t have the paper backing on it – that can create a moisture trap – so this is what we call unfaced. Then you need all the right equipment. You know, the goggles like this, kind of goofy looking, but they are pretty good to keep the fibers out of your eyes. And, of course, the dust mask, your gloves, you need a good sharp knife.
And what’s the baby powder doing here? Well, you need to wear long-sleeved shirt, long pants and everything, but you still may have a little bit of skin that’s still exposed. Put a little of this on your wrist maybe on the back of your neck and around a little bit. You know, you’re gonna smell kind of nice, but also it’ll keep the fiberglass from irritating your skin.
After that, all you do is cut it out, roll it out perpendicular to your joist, and you start saving money on your energy bill.
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