First let me say there's a lot of competing information on which is better, fiberglass or cellulose insulation. Both can be blown into existing walls and attics without significant demolition. The people who mainly sell and install cellulose insulation think it's worlds better than fiberglass and those that manufacture and install fiberglass insulation think that's the best choice. I'm still trying to make up my mind what to believe but both options can be DIY projects and both choices offer a free blower rental with a minimum purchase from Home Depot.
Insulation recommendations changed a few years ago. If your home was built before 1990 there's a good chance you don't have enough attic insulation. If the level of insulation in your attic is at or below the floor joists, you don't have enough. If you can't see your floor joists in the attic because they're covered with insulation you're probably good.
If your home was built before 1980 you may not have any insulation in your walls. If your home was built before 1960 you more than likely don't have insulation in your walls. There's really no way to tell without making a small inspection hole in an exterior wall and visually checking.
To add insulation to existing walls without having to tear down all the drywall the only two affordable choices are blown-in fiberglass or cellulose insulation. Foam is way too expensive for me right now.
Here's what cellulose and fiberglass insulation is currently selling for at Home Depot in my area:
$11.48 for GreenFiber Blown-In Cellulose Insulation
$29.68 for Owens Corning AttiCat Fiberglass Expanding Blown-In Insulation System
When I first saw those numbers I got excited and thought I could blow in cellulose for a lot cheaper than I previously priced fiberglass. Unfortunately you need a lot more cellulose packages than you do fiberglass because the fiberglass is compressed. When it comes to walls it gets even worse which I'll explain after we look at the numbers for attics. Let's say we have a 1,000 sq ft attic we want to insulate by adding an additional R-30 worth of insulation. Here's what the numbers look like.
Attic Insulation Cost Comparison
|AttiCat R-30||16||$29.68||$474.88||$30.24 (5.99%)|
|OC Fiberglass R-30 Batts||29||$15.98||$463.42||$41.70 (8.26%)|
|AttiCat R-38||20||$29.68||$593.60||$83.72 (12.36%)|
|AttiCat R-49||26||$29.68||$771.68||$158.20 (17.01%)|
The costs above only reflect the cost of the insulation. You get a free 24 hour blower rental if you buy 20 bags of GreenFiber or 10 bags of AttiCat and we're above both of those and I assumed you'd need to rent a truck for either if you don't already have one. Although you're getting a lot more packages of GreenFiber so for some people, that may mean having to rent the HD truck instead of using their own truck.
R-30If you're only adding an additional R-30's worth of insulation the cheapest option is to use Unfaced R-30 Batts that you just roll over your existing installation (perpendicular to your joists.) if you don't mind crawling around cutting insulation.
If you'd rather blow insulation, AttiCat is slightly less than GreenFiber and not much more than R-30 rolls. Not a big enough difference to choose one over the other if you have a certain preference for either fiberglass or cellulose in my opinion.
R-38 and R-49
At R-30 you need about 2.75 times as many GreenFiber bags as you need AttiCat. At R-38 it's 2.95 times more and at R-49 it's over 3.1 times as many packages.
I think the labor will become an issue as well with cellulose. You have to load, unload, carry and feed about 3 times as many bags of GreenFiber as you do AttiCat.
Wall Insulation Cost Comparison
|AttiCat R-13||27||$29.68||$801.68||$323.68 (28.77%)|
|AttiCat R-15||31||$29.68||$920.08||$204.96 (25.58%)|
Cellulose insulation settles a little bit compared to fiberglass so you really have to pack it in. When you do that, the settling is minimal. I'm guessing that's why it takes much more cellulose insulation compared to fiberglass.
Either GreenFiber or AttiCat is going to be better than not having enough attic insulation or any insulation in your walls if you live in a colder climate. Both can be installed by DIY'ers who spend time reading the instructions and preparing beforehand.