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A while ago, there was a post where someone detailed what his wall construction consisted of. A component of it was the rigid foam insulation on the outside of the sheathing. Mike Smith replied with the construction he uses; which is to have the rigid foam insulation on the inside on top of which is furring for the drywall. I’m in the Richmond area of Virginia, where (as a Limey) it doesn’t get awfully cold neither is it unsufferably hot, but both heat & a/c are needed. I’m about to start drawing my plans and would like to know what would be the best construction, particularly with respect to vapour barrier placement. I’ll use blown cellulose if I can afford it, fibreglass otherwise. Do I need the barrier if I use cellulose? Believe me, I have read all the posts but it still isn’t clear to me, especially in a heating & cooling environment. For the rigid insulation on the inside, again if I can afford it, what’s the best type to use, the best or most economical thickness, the best way to hold it to the studs and what size should the furring be and should it be horiz. or vert.? Is any special detailing needed at openings or is the rigid foam & furring stopped at the R.O. and it’s all covered up by jambs?
As always, I appreciate you guys taking the time to read the post, think about it & reply.
David
Replies
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david.... i've used foil-faced polyiso in the past...
but since comming here i've done a lot more research on EPS...
from here forward.. when i get a job that calls for an energy wall i'll be using EPS with a density of 1.5 lb/cf..
in this job ....
http://webx.taunton.com/WebX?233@@.eed77d3/126!enclosure=.eef6f7e
we used 1.0 lb./cf
because it was the cheapest... but it is harder to handle because it isn't as strong as the 1.5..
my thinking is that an energy wall... cost efective... will be 2x4 @16" oc..
with densepak cellulose...
and a thermal break of 1 inch foam on the inside....
some apply the drywall right over the foam.. with long screws...
...i like the furring so i can apply trim and other interior details without trying to find the framing 1.5 inches away..
the furring definetly adds to the cost....
but i like it better than a 2x6 wall
there are lots of different techniques for energy walls... this is our latest evolution ...the first one we built was in 1974 with 2x6 @ 24" oc...and fiberglass insulation....
in a competitive market... cellulose should be cheaper than fiberglass... and ....always better..
b but hey, whadda i no ?
*Mike, thanks for the reply. Just what I needed to know. What do you think about a vapour barrier if I used cellulose? Is it needed & where; or is the EPS a barrier? Thanks Mike & I don't mean to bug you with these run of the mill questions.David
*david.. with fiberglass we always use a continuous vapor barrier of 6 mil poly..with cellulose.. we don't use one unless the building inspector wont accept it...the eps is a vapor barrier.. but you have to tape the joints if you want it to act like that....i don't worry about taping the joints because with the dense pak cellulose there is not going to be any air moving.. so not enough moisture will penetrate the wall that the cellulose can't handle....instead we concentrate on controlling moisture sources.. like bath fans... cooking exhaust.. and of course.. basement and crawl space vpaor barriers and control of ground water and rain run0-off...
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A while ago, there was a post where someone detailed what his wall construction consisted of. A component of it was the rigid foam insulation on the outside of the sheathing. Mike Smith replied with the construction he uses; which is to have the rigid foam insulation on the inside on top of which is furring for the drywall. I'm in the Richmond area of Virginia, where (as a Limey) it doesn't get awfully cold neither is it unsufferably hot, but both heat & a/c are needed. I'm about to start drawing my plans and would like to know what would be the best construction, particularly with respect to vapour barrier placement. I'll use blown cellulose if I can afford it, fibreglass otherwise. Do I need the barrier if I use cellulose? Believe me, I have read all the posts but it still isn't clear to me, especially in a heating & cooling environment. For the rigid insulation on the inside, again if I can afford it, what's the best type to use, the best or most economical thickness, the best way to hold it to the studs and what size should the furring be and should it be horiz. or vert.? Is any special detailing needed at openings or is the rigid foam & furring stopped at the R.O. and it's all covered up by jambs?
As always, I appreciate you guys taking the time to read the post, think about it & reply.
David