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CharlieR 03-25-2012 03:14 PM

Attic Insulation

Sooo... my attic rafters are only 2x4's. I'm re-doing a bathroom, and removed the insulation from above (had to take the ceiling down). So about to put it back and my question is... is there any point in putting thicker than 2x4? I believe that if the insulation isn't compressed between the 2x's that it doesn't get the proper R value?

At the big orange, I only managed to find 2x4 with 24" spacing that was R-12...they didn't even have R-14. Is there any benefit in getting the 2x6 at 24" which is R20 or will I not really get that anyhow? NOt to mention it will be sitting above the joists... I will likely blow in some insulation anyhow... so should I just use the R-12 and blow in more, or use the R-20 and blow in less? Am I overthinking this? (I do that a lot :huh:)

Gary in WA 03-25-2012 07:51 PM

I'd use the cellulose and fill as location requires per code. Are there ceiling joists and rafters?

A picture would help!


jklingel 03-25-2012 09:48 PM

But remember that codes are minimums. Go with as much insulation as you can afford as per the period over which you will be calculating your ROI. Mega-insulation gives good karma.

Windows on Wash 03-26-2012 08:29 AM


In Canada, the least I would put up there would be R-50.

creeper 03-26-2012 09:47 AM

Minimum code in Ontario is r-40, but you don't specify where in Ont. It will make a huge difference if you are in Windsor or Wawa. Lots of people don't realize that most Ontarians live considerably south of the States northern mid-western borders.

M3 Pete 03-26-2012 01:43 PM

the size of your rafters have NOTHING to do with how much insulation you should have. Unless you have something pressing down on the insulation, it will stay uncompressed, and give you insulating value.

I have R-19 batts (6.5 inches) between 2x4 trusses, and it works very well.

But if you are going to blow insulation in there, why bother with using batts? Why not just use the blown in?

And like the others said, R-40 to R-50 would be my goal if I lived where you do.

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