Final, I hope, chapter on this subject. I asked this question several weeks ago and rec’d some info from Gabe Martel and others.
The time has come when I must make a decision. I am going to do a sealed attic, w/ the insulation applied to the underside of the roof decking.
Apparently, PolyU is better, technically, than Icy. But, it costs more. Also, it appears that the installation of the PolyU is messier – at least for the installer, who must wear a full monkey suit and PBA for respiratory protection. Both seal all the cracks if they are installed correctly.
Given these facts – is the increased cost of the Polyu worth it over the Icy? My conclusion is that both foams are a better value than wet blown cels, which in turn makes FG look like the loser of all times.
Don
Replies
Don,
I too am building a house and plan on foaming the underside of the roof decking. House is in Houston and I intend to use Icynene. I have not heard of the PolyU, but will explore it. Have you ever talked to any one who has had a foam job, such as ours, for an extended amount of time, i.e., someone who has seen if the foam deteriorates or cause other unwanted problems?
Thanks,
Greg
last year there was some discussion and some vendors piped in with this info:
Polyurethane - close cell foam
Icynene - open cell foam
the plus for my mind was that an open cell foam can breathe a little bit and so if any moisture got into the cavity it would be able to get back out again faster than the closed cell would allow. I went with (as have many others living around me that I have talked to lately, in SE Michigan) the Icynene product this last year. I'll let you know in ten years how it holds up.
One side note, Icynene cures and gives off steam and carbon dioxide. Both are relatively save and breathable (although it does smell for a day or a week depending on the air flow thru your structure, which can be a little irritating to residents). On the other hand, I don't know what PolyU is off-gassing when it 'kicks'. If he has to wear a smurf suit and breathing apparatus its probably poisonous, a thing that I usually want to avoid living very close to.
In the '70s, there was a spray foam used that off-gassed urea-aldehydes which caused sickness in some occupants, and was (I think) banned. I wonder what the Poly U is doing? Even if it is non-poisonous is it also ozone-safe?
I think it was a urethane foam that had bad off-gassing problems years ago. The current poly urethane is much better and is stable shortly after spraying. I just learned yesterday from a foamer that BASF will soon introduce a foam with a new blowing agent that reduces or eliminates the off-gassing from spraying the poly. We use a lot of it, so I look forward to that. We use the poly be/c we need the closed cell and the greater density for our particular application. The foamer sprays both and would choose Icynene for his own wall cavities in a frame house.