Suprathane Brand Rigid Foam Insulation
I’m mostly just curious if anyone has heard of or encountered this brand of rigid insulation before and what the true R-value is?
https://journals.sagepub.com/doi/pdf/10.1177/0021955X7501100402
While crawling around the attic to install insulation baffles, I was able to pull a sticker off the backside of my homes rigid insulation sheathing and found the name Suprathane. There’s very little info on the web other then the attached article. I have a very difficult time believing the claimed R- value of 13.2 and suspect I should be considering it probably closer to typical polyiso at 6.5/inch. My house was built in 1978. 2×4 construction with r-13 batts, 1 1/4″ (suprathane) and all brick exterior.
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Back in the day, polyiso claimed inflated R values. Later, during the '80s if I remember correctly, the NRCA (a roofing trade association) pushed for the use of LTTR (long term aged) R values to be used instead of initial values right after manufacture (which tend to be higher for polyiso compared to aged values). Ultimately, the manufacturers started using a standardized LTTR testing methodology to come up with more realistic R values, which are what you see today.
I wouldn't be at all surprised to see 70s vintage materials with higher than expected labeled R values. I have on my own home some 1978 vintage 1/2" polyiso that is labeled as R5, for example. Modern 1/2" polyiso is labeled as R2.7. The only real difference (besides the older stuff being a bit yellowed on the edges), is that the older material has a thicker foil facing compared to modern stuff. If I were to measure the R value of the old stuff, it would probably measure very close to the newer stuff's rated R value.
BTW, "R13" worth of polyiso is 2" with modern ratings. 1.25" polyiso would likely be rated R7.5, maybe R8. One advantage with the old stuff is that it didn't have an issue with cold weather derating due to the different blowing agents that were used back then.
Bill
This is an interesting tidbit of history- I wonder if this type of testing is what garage door manufacturers do to bolster their ratings.
There was a big "fight" between manufacturers and some groups that wanted more realistic R value numbers. Tha NRCA was probably most responsible for pushing the polyiso manufacturers to be more realistic with their R values. NRCA still thinks the numbers are a bit optimistic, but they're much better than they used to be.
Bill
LTTR is better than nothing in terms of estimating the long-term R-value but it's still not perfect; it's an 18-month test simulating 5 years of use/exposure. The foil facing slows air from replacing the blowing agents in the tiny foam bubbles that create the higher R-values, so eventually the R-value will be even lower than the LTTR. But the LTTR is much more accurate than conventional testing, which is completed six months after manufacturing but with carefully protected foam that likely still has almost all of its initial blowing agent filling the cells.
Thanks so much Bill. That’s exactly in line with what I expected just wanted to verify.