Insulation in attic


Old 03-09-06, 06:13 AM
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Join Date: Mar 2006
Posts: 34
Insulation in attic

I am having a home built in the far west burbs of Chicago and the builder uses batt insulation in the attic with more insulation blown over the top. These two combined make-up a R-38 value. I have read that R-49 is recommended in our area. Should I inquire into upgrading or maybe possibly blow in more myself? Will the extra insulation make that dramatic of a difference? Thanks!
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Old 03-13-06, 02:22 PM
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Join Date: Mar 2006
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Is there a significant difference between R38 and R49?
Old 03-13-06, 06:55 PM
Join Date: Sep 2005
Location: ohio
Posts: 195
Whats the R value of the current insulation? Usually its way cheaper to just have more blown in when you are actually doing it as its just adding a few more bags to get the height necessary. If you didnt have anything up there for instance R38 would require you to blow in 11.4 inches (before settling) and R49 is 15 inches. Find out the total square footage your installer is using to base his estimate for R38 also ask how much more money its going to be to get R49.
Now the sq ft is important cause it will tell you how many bags it will take to blow in R11 yourself (no less than 3.3 inches more). At R11 one bag of coccon cellulose insulation will cover 69 sq ft so the calculation is Sq Ft(area of attic)/ 69sq ft per bag= number of bags required.
Say you have 500 sq ft attic : 500/69sq ft bag= approx 7.3 bags.
Find out the cost of the cellulose insulation from your local store; around here it is $7 per bag and you have 56 bucks (~8 bags)for getting R11 more to give you R49 by blowing it in yourself. Dont forget that you also have to probably pay to rent the blowing machine usually around $20 for such a low amount of insulation ( 20 bags here gets me a free day use of a machine)
So all in all you are looking at a little over 80 bucks with tax to do it diy for a 500sq ft attic space. Now all you need to do is figure out what the guy is going to charge YOU to do it. Again find out the sq footage of your attic and do this calculation on your own.
Now in terms of if its worth it? I dont know but with the cost of heating so high id rather have the recommended R49 than R38. Also Make sure you ask him about air sealing that attic correctly with caulk and foaming before to enure your insulation will actually work as drafts flying thru any kind of insulation wont be much good.
Old 03-14-06, 05:23 AM
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Join Date: Oct 2004
Location: USA
Posts: 322
You can't go wrong with more.

If it was going to cost me $100 to DIY, I'd pay up to $300 to have the builder do it.
(I would, don't know if you would)
Does not sound like a fun job to me. considering the setup costs are already accounted for,
it should not be significantly more to blow up to R49 at the same time.

Make sure they don't block the eaves. They should install air vents along the roofline to allow air to circulate above the insulation.

enjoy your new home!

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