Spray Foam vs. Fiberglass, anyone done the math?
OK, read the entire thread, and while I don't have much to add a lot of what has been said in here isn't terribly accurate.
One thing I can tell you from experience is this. Many years ago our trusty Canadian Government partially sponsored the installation of UFFI (Urea Formaldehyde Foam Insulation). It was intended to go in to older homes which had either no insulation at all, or possibly the aluminum foil that used to be popular back in the day.
When installed correctly, it only did a so-so job - and I will say why in a second. When installed poorly it was totally useless.
Not only that, but it became dangerous in the event that any moisture got into a UFFI'd cavity.
Subsequent to getting many complaints about UFFI, our trusty Canadian Government (federal) did an about face and then had to sponsor part of the cost for removal of this self same product. I was one of a relatively small handful of people who got a license to remove UFFI. Let me tell you, it was NOT a fun job.
A homeowner could take the UFFI course and be granted a license to remove the UFFI from his own home and thus take advantage of the $5,000 grant for removal. But he could do no others. The course was intended for trades people, typically carpenters.
What I found was borderline disgraceful. It was always easy to tell when the installer knew what he was doing, because the cavities would be correctly filled. When they had no clue, well, some of the messes we uncovered were downright criminal. It was one of those times in our past construction history that every crook wanted to get in on the act and make a quick buck. OK, maybe that's stretching it a bit, but there were more lousy installs than good ones.
Here's what happens with the UFFI installs, and remember this is from personal experience.
I do not ever remember opening any cavity and seeing the whole thing 100% filled. The foam would invariably pull away from one or both sides of the studs, or it would be cracked into large pieces. Please be sure to understand that this had nothing at all to do with any stud shrinkage, as these houses were likely 30-40-50 years old before the UFFI install. The cavities would have been as dry as a bone. A very old bone at that!
So, from observation, I can say that this particular foam definitely shrank once it dried out.
It also caused some serious health problems if a cavity ever got damp or wet. I did find one such case in Trail, where the husband's bedroom was right next to a UFFI'd wall and the stucco outside had a massive crack down the entire wall. He got sick shortly after the install, and neither he nor his nurse wife could figure out what was wrong. His first night in that same room after we pulled the foam out eliminated the trouble, just like that. That was the only case of illness that I encountered, but many others were reported to CMHC as the removals took place.
Whether or not the current batch of foams act any better, I really do not know. But there has been a lot of chat in this thread about lumber shrinkage. If you use KD lumber, surely that shrinkage must be very small. Why could a foam not adhere to the studs in such a case? Is there no flexibility in the newer foams?
I'm in the process of designing a net zero energy home and I came here looking for help with insulation, particularly cellulose. I will post a new question about that.
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