Polyisocyanurate IKO Enerfoil vs IKO Ener-Air?
kipstiggak
| Posted in General Questions on
I live in Quebec northwest of Montreal where it’s next to impossible to buy Polyisocyanurate but a local store ordered it from IKO. After several weeks it finally arrived but it turns out to be IKO Ener-Air. The store owner said I could return the Ener-Air but he can’t get me the Enerfoil for some complicated reason. I’ve already installed 2″ EPS foil-faced rigid foam on my concrete block walls and was ready to add 1″ Polyiso. So the question is can I use it as is or can I add foil to the IKO Ener-air to make this work ?
Thanks,
Dom
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Replies
Which side of the walls are you installing this? Inside or outside? Probably no need for the foil, but I want to be sure I understand what you are doing.
Inside.
Good. It will work well there. And you don't need the foil.
While advertised as "breathable", the specs only guarantee that it'll be above about 1 US perm, which is fine, but not super-breathable. The actual permeance will vary with thickness.
In this application since you already have 2" (R8-ish) foil-faced EPS against the foundation, the vapor permeance of the next layer is moot- it doesn't really matter. The ground moisture will be blocked by the foil facers, and with only 1" of polyiso (R6) on the interior there is no chance of the "cold" side of the polyiso loading up with wintertime moisture from interior moisture drives, even on the above-grade part of the foundation. More than half the total-R is on the exterior of where EPS & polyiso meet, and it's average temperature in winter will be well above the dew point of the conditioned space air.
I should have mentioned that that walls in question are completely above grade. It's a bungalow with a crawlspace. and the walls from top to bottom are made of cinder blocks. The crawlspace walls have been spray-foamed 4" thick. If this doesn't change things then it's great news!
Thanks guys,
Dom
I should have mentioned that that walls in question are completely above grade. It's a bungalow with a crawlspace. and the walls from top to bottom are made of cinder blocks. The crawlspace walls have been spray-foamed 4" thick. If this doesn't change things then it's great news!
Thanks guys,
Dom
You still have more than half of the total R on the exterior of the foil facer, so adding R6-ish polyiso isn't a problem.
Tape all the seams and seal the edges to discourage air convection into any gaps that open up over time.
Thanks for all your help, really appreciate it.