Icynene vs. polyurethane foam insulation
I’m planning on finally insulating my 150 year old uninsulated home after paying some outrageous gas bills this winter. After reading many of the archived threads on foam insulation, I was sold on polyurethane. I called a family friend who works for a large local foam outfit for a price quote-I trust this guy isn’t trying to give me the runaround. He told me his company won’t do poly under a roof deck, they only do Isocynene there (they handle both products). His reasons were twofold. First, if the house does any settling, he says it could crack the poly and render it less effective, whereas Iso is more flexible and forgiving. Second, they are worried that if you got a roof leak, the open-celled Iso would allow you to localize the leak but the closed-cell poly could allow the water to migrate elsewhere before entering the attic. I’ve not seen either of these issues addressed here before (but I haven’t read every post on the subject). I considered buying the DIY Tigerfoam poly kits, but my materials costs alone would be 1.5 times material and labor for Iso of equivalent r-value. Since this will be sprayed onto an unvented roof deck, I liked the superior vapor barrier and stiffness provided by poly, but will I be just as happy with the Iso? Any advice/thoughts on the subject would be most appreciated.
Conrad
Replies
Don't quote me on this, but I was at a Lstiburek seminar a couple of years ago when he was talking about different types of foam and it seems to me he said basically what your guy told you. Vapor permeable foam is good in some places and not so good in others. In a basement, you want vapor impermeable foam, under a roof deck, vapor permeable foam would be a better choice.
If your guy sells both types, he's got nothing to gain by selling you one type for one part of your house and the other type for a different part of the house. Nothing to gain except fewer callbacks and a happier customer that is. Right?
We should probably do an article about it one of these days.
Associate editor
Yes, please do...preferably before we move on to do our basement....(grin).
We live in earthquake country and used open cell because of the shaking factor...
I suppose closed cell would have added to the overall rigidity of the structure, but that wasn't really a problem.I also really liked the zero outgassing at 7 days of the Icynene and could never get as comfortable with the closed cell product.
NotaClue
Hi Dan, It's been so long since you've left tacks here that I was starting to wonder if the earth had swallowed you up! You been home lately?Those are some good points that I have never considered before
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Over in the JLC forums it has been pointed out that in the colder climates (IIRC 7500 HDD, but that might be wrong) that the open cell foam require a paint coating to additionaly reduce moisture transfer.That over a hard winter that enough moisture will migrate through the open cell to condense.Suposity the Icynene has this written up.
Icynene says you only need the imperm paint for Madison WI and colder.
Hi,
This insulation guide seems (to me) to favor the urethane:
http://www.builditsolar.com/References/InsulationTypesEEM-01454.pdf
R6.2 vs R3.6, and a slightly more suitable rating for roof and catheral ceilings??
Gary