I need to replace a 7 x 12′ ceiling over a stairwell. Rafters here are full dimension 2 x 4s. In order to get some insulation here–where there was none–I thought of reframing the ceiling about a foot below the rafters. Then after hanging the DW, blowing cellulose into that space.
I’ve blown cellulose into an attice but never tried anything like this. Presumably I’ll just need to cut a few holes in the DW to blow the stuff? What I found in the archives makes me think this should work. Any tips? Hole spacing?
(I am familiar with the cathedral ceiling venting debate, and plan to NOT vent this.)
Thanks.
Replies
Why not just put some fiberglass ins. before the drywall? It's better than blown in, doesn't settle over time and you don't have to punch holes then patch them.
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Why not just put some fiberglass ins. before the drywall? It's better than blown in, doesn't settle over time
Whoa daddy -here we go - hold on. It's gonna be a bumpy ride.View Image
Why not just put some fiberglass ins. before the drywall? It's better than blown in, doesn't settle over time
Whoa daddy -here we go - hold on. It's gonna be a bumpy ride.
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Seat belt buckled, helmet on... I'm ready for it. :)
but now that we know there is a blow-in machine already on site, it's a whole different story. I still say fiberglass is better, but if the machine is already there then blown-in does seem the easier way to go. And with such a small area I think the difference in performance is pretty much moot. Blow it in, be done with it.
Then again, if there is some fiberglass already on site...
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Edited 9/11/2008 3:15 pm by Ted W.
"I still say fiberglass is better,"What is you basis for that? Air infiltration, usage of recycled materials, ease of tight installation, or something else?
Jon Blakemore RappahannockINC.com Fredericksburg, VA
ted... why would you say fiberglass is better ?Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
It doesn't condense over time.
I've seen too many attics with blown-in which used to be the full depth of the joist, now only half that. Wall cavities between the studs where the blown-in is only 2/3 of the way up, where I have to assume it used to be full. And this isn't turn of the century stuff. I'm talking housed built in the 50s. And when you lift up some of the blown-in you can tell it's dense and compact.
This doesn't happen with fiberglass, at least not that I've ever seen. That's my only reasoning. Other than that, I'd like to know why some might thing blown-in is better. Of course, it's better at filling every cavity. But if properly installed, fiberglass will do that just as well. See my work at TedsCarpentry.comBuy Cheap Tools! BuildersTools.net
"But if properly installed, fiberglass will do that just as well."I think that's the problem right there.Very often, fiberglass is not properly installed in wall cavities. Not the fault of fiberglass, but is endemic to the system that relies on perfect cuts.Secondly, fiberglass does not do a good job at cutting down air infiltration. Granted, cellulose is not as good as properly installed foam, but I do believe it's better than FG.I think the settling problems you've seen in cellulose are just like the installation problems that fiberglass has. You can work around them, but some don't. In my opinion, I believe it's easier to adapt to the needs of cellulose than fiberglass.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
Very often, fiberglass is not properly installed in wall cavities. Not the fault of fiberglass, but is endemic to the system that relies on perfect cuts.
You mean like this?
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You say'n that ain't purefeckt??!! Can't believe it. go figure (no I don't think you are an abacus). ;) nyuk
ted....if you study the literature you will find that cells has a settled density of about 2 lb/cf
a good installer will do a bag count (lb's of material printed on each (bag ) bale
total lb / area will tell you what the settled density / r-value will be
nowadays we blow about 24 inches in attics...and we always do a bag count so we can verify that our settled density ( and depth ) is going to wind up at about 20"
(r 60 )
there are no gaps.... it's pretty much fireproof.....no vermin ( borates )
no air infiltration
in open attics...there is nothing better.....nothingMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
cellulose doesn't condense at all ... as it is not a liquid. Am I missing something?
"I'll just need to cut a few holes in the DW"
and
"Then after hanging the DW"
Just thinking how funny this must sound to the guy who recently asked what does DW mean?
Pertaining to your post though, in a 7' x 12' area, it is not worth the time and aggravation to blow in insulation. Just frame it down like you said then stuff in the most fiberglass as you can properly fit. In such a small space, if you are really wanting to seal in the heat, maybe use rigid insulation and seal it with spray foam. Remember the "weakest link" theory though. What is the R-value of the rest of the house? If it's low then better to spread out the time and money to bring everything up to par than to super-insulate just one spot.
gk
I've got more attic insulation to do, so this bit of ceiling is kind of a 'as long as I've got the machine........'. I really just want to make sure that it is possible to do it this way.Thanks.
Yes, it's possible. Use 5/8 board if you're going to dense pack it.
Joe H
I would suggest instead of hanging the ceiling, you use a plastic vapor barrier instead. I have used reinforced poly. You can staple or even use plasticap nails to fasten it a bit up the side of the joists so that it is stretched quite taut. Then cut one hole in each joist space, and fish the hose to the end. Blow until the cellulose quits coming out of the hose, pull it back, and keep repeating until you have the cavity nice and packed. Then you can go back and tyveck tape the holes you made. Another way to go would be to install the poly, and then nail 1x2's to the bottom of the joists.
Seems like a very small area ... one hole per bay should do it ... in the center ... run the hose in fully one side and draw back and then put it on the other side, ditto. Pretty straight forward.
Option: glue rigid to the ceiling and install DW ... up w/ e.g. 3" screws ... can you get longer? I've done that before.
You got it going on and your reasoning is fine ... do what works ... I don't think you can go wrong; plenty of easy options.