Cellulose and weight = problem? - Contractor Talk - Professional Construction and Remodeling Forum

tgeb · 01-09-2009, 07:06 PM

I am having some additional insulation blown into my attic.

I got 2 quotes and both contractors quoted fiberglass instead of cellulose, from my research here and other places I understand that cellulose is better.

When I brought this up the contractor who I intend to use said he did not like to put cellulose in the attic due to the weight of the material. (he will be adding R-19 on top of what is there, to a total of R-38. But some places actually have none at this time, so those areas will be R-38 cellulose)

My attic framing is "stick built" 2X6 for ceiling joist and 2X8 rafters, 16" centers, but only 3/8" sheet rock above the living spaces.

Do you think this will present an issue some where down the road? I don't want my ceiling looking like a wash board in a few years.

Price is the same with this so the only issue is....Is cellulose the right thing in this application.

And no I'm not going over to DIYChatroom.

WXdan · 01-10-2009, 12:49 AM

Hi tgeb,

I'm gonna guess that your contractor doesn't usually stock cellulose, and that's why he's pushing the fibo. Blown cellulose goes at (conservatively) R 3 per inch. If you are looking for R 38, you are going to have at the most 13 inches of cellulose at a density of less than 2 pounds per cubic foot. Some simple math...tells me that that will end up being a little over 2 pounds per square foot of ceiling area (1'x1'x13"). No worries on the sheet rock. The place I work for has been blowing cellulose since the 1980's and the only ceiling weight issues we have is when one of our techs puts his foot through the ceiling.

A side note, whatever you blow in an attic will get into the home occupant's lungs (uncomfortable for us insulators to say, but true). I would rather breath cellulose (recycled newspaper with borax) than fiberglass.

DavidC · 01-10-2009, 08:07 AM

We choose cellulose over FG at every opportunity. IMHO it's simply a better product that has fewer install problems. I agree with WXDan's assessment.

Good Luck
Dave

TimelessQuality · 01-10-2009, 09:05 AM

3/8" rock may sag over time... Especially if you have a high humidity area (bath) or event (water leak).

tgeb · 01-13-2009, 07:53 PM

Thanks for the feed back guys. How ever I made a mistake in the R value I quoted in the original post, and we actually should have R-49 total in this attic.

Does this change your opinions at all?

WXdan · 01-14-2009, 12:11 AM

No opinion change from me.

DavidC · 01-14-2009, 06:42 AM

Same here. I have more than that over my own kitchen.

Good Luck
Dave

bighammer · 01-14-2009, 08:13 AM

intake, exhaust, proper vents, make sure you have adequate ventilation...you could ruin everything if this is not done properly.

I wonder why they used 3/8" SR on the ceiling areas? Good luck and keep us posted on what you do...

parts · 01-27-2009, 07:55 PM

Weight should not be a problem with 3/8 Sheetrock when it's 16 OC. The 3/8 is existing? Or to used just to match whats there already?