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Is it very beneficial to insulate attic more in this case?

Is it very beneficial to insulate attic more in this case?


Old 02-27-10, 06:01 AM
Thread Starter
Join Date: May 2009
Posts: 3
Question Is it very beneficial to insulate attic more in this case?

There is blown fiberglass insulation to a depth of about 12" in my attic. The roof joists are about 5 feet above the blown insulation. There is no insulation between the 2x4's supporting the roof. They're 24" apart. Would it be a good idea to insulate between these joists?
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Old 02-27-10, 07:20 AM
Join Date: Oct 2008
Location: New England
Posts: 9,991
Hi Chris, generally, the outer perimeter of your attic, along the soffits is one of the more difficult areas to insulate and one of the most important. Exterior wall/ceiling junctions always show excess heat loss. The problem is, the wood framing limits the amount of insulation and the air venting in through the soffits can go right through the insulation, especially the fiberglass. It's a difficult area to get to, but what is ideal is a baffle up against the bottom of the roof to protect the air flow and another over the exposed end of the insulation to keep the incoming air out of the insulation. The effect is called wind washing.

Fixing the above area and locating and sealing all air leaks would be the most important. As for the amount of insulation needed, your location will tell us the current recommendation, but IMO, there can't be too much. It's a numbers game. If adding another foot will cost $1,000 but only save $50 per year, you have a simple payback of 20 years. Some might go for that. But the next foot, another $1,000 might only save $20 per year and most would say that is not worth it. Of course the cost of energy could double and suddenly the Savings to Investment Ratio changes, so I say, do as much as you can while you are there. I'll add a link that will illustrate the diminishing returns for adding and adding.

Here is another link on air sealing. Slow to open, but lots of good information.


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