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I posted this question over at JLC as well, but we seem to get more traffic here.
A couple of questions relating to cellulose insulation.
In the February edition of JLC is an article about energy sealing houses. The author (Paul Bourke) uses a reinforced poly air barrier and dense packs dry cellulose into stud bays.
In the April/May 2000 Fine Homebuilding, Fred Lugano claims no poly is needed — that the dense packed cellulose is the air seal. He uses the drywall to hold the cellulose in the stud bays. I can understand using the reinforced plastic to hold the cellulose in place, but Mr Bourke goes to great lengths to seal every little edge and penetration. I admire his meticulosity (is that a word?) but is it necessary? Does dense packed cellulose act as an effective air barrier or is the poly needed?
What about wet blown cellulose? How does it compare to dry blown? Does it achieve the same density of 2-1/2 – 3 lbs per cubic foot? How long does it take to dry and how does it affect things like hardwood flooring? Does it settle over time?
Thanks,
Dan
Replies
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Dan,
I have pondered the same thing, and the conclusion I have come to is not to use a poly barrier with DP cells, for a couple of reasons, first because I don't think it is needed if the cellulose is blown in to a high enough density, and second because I believe it hinders the ability of the Cellulose to dry to the inside when condition so permit.
Certainly the poly barrier will make for a more airtight assembly than the Cellulose alone, but I believe that is outweighed by the potential for the poly to trap moisture that may get into the assembly in any number of ways other than on gross air movement.
I have no data to back this up. It's just my gut reaction to everthing I've read and seen and the discussions that have transpired on this board.
Steve
*Dan, I agree with Steve 100%. I have used wet spray cells in the walls of my homes for 16 years. It is extremely inportant that no poly barrier be placed over it. It needs to dry to the inside and can take weeks to do so (my locale is a heating climate). I have used lots of hardwood floors with no ill effects from the cells. Monitoring the moisture content in the subfloor is very important.Last summer I put a room addition on a home I built 9 years ago. We took out about 14' of an outside wall to make the opening into the new room. Even after removing the drywall, the cellulose was all perfectly in place and set up very firmly. If applied correctly it cannot settle. We had to dig it out of the cavities. There were no signs of any moisture penetration, or dirt tracts like you see with fiberglass. The studs and sheathing looked brand new. We tighten the homes until an ALR is "1" or under calculated using a blower door test. Cellulose and air sealing are the keys.
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I posted this question over at JLC as well, but we seem to get more traffic here.
A couple of questions relating to cellulose insulation.
In the February edition of JLC is an article about energy sealing houses. The author (Paul Bourke) uses a reinforced poly air barrier and dense packs dry cellulose into stud bays.
In the April/May 2000 Fine Homebuilding, Fred Lugano claims no poly is needed -- that the dense packed cellulose is the air seal. He uses the drywall to hold the cellulose in the stud bays. I can understand using the reinforced plastic to hold the cellulose in place, but Mr Bourke goes to great lengths to seal every little edge and penetration. I admire his meticulosity (is that a word?) but is it necessary? Does dense packed cellulose act as an effective air barrier or is the poly needed?
What about wet blown cellulose? How does it compare to dry blown? Does it achieve the same density of 2-1/2 - 3 lbs per cubic foot? How long does it take to dry and how does it affect things like hardwood flooring? Does it settle over time?
Thanks,
Dan