Replies

1. GBA Editor
   Martin Holladay | May 05, 2016 11:43am | #1

   Bill,
   As far as I know, there aren't any performance differences between these brands.

   That said, green builders usually try to avoid using XPS, because XPS is manufactured with a blowing agent that has a very high global warming potential. Either EPS or polyiso are preferable from an environmental perspective.

   For more information, see Choosing Rigid Foam.

2. 
   charlie_sullivan | May 05, 2016 10:35pm | #2

   If you must use XPS, Owens Corning Foamular uses a blowing agent mix with something like 45% lower global warming potential than the one used by Dow and presumably also Kingspan.

   It's a little hard to tell exactly what the numbers are, but the Foamular literature claims their mix has a global warming potential (GWP) 70% lower than the pre-2009 HCFC blowing agent (142b), which had GWP = 2310. 70% lower would be about 700. On the other hand, the XPS industry association says that the GWP of the blowing agents their members use range from 740 to 1340. I suspect that the 740 is for Foamular, and Owens Corning is rounding the 68% improvement that represents up to 70%. 740 is 45% lower than 1340, which is the GWP of the HFC-134a blowing agent used by Dow and presumably also Kingspan.

   But that's all misdirection on the part of Owens Corning, with me playing right into their marketing strategy by giving it more attention than it deserves. So I'll stop now and note that the real solution is to follow Martin's advice and use EPS or polyiso. If you want about the same R-value per inch as XPS, you can also get graphite infused EPS, often under the trademark Neopor. Any of those have about 99% lower GWP than any of the XPS available in North America.

3. 
   Chaubenee | May 05, 2016 11:51pm | #3

   Look for recycled EPS better yet. Often they tear down old warehouses and refrigerated warehouses in places like New York where there is insulation like that on the roof under the rubber roofing. Then a goal guy buys the stuff to sell on the secondary market. Look on Craig's List as a starting point. I bought my 2.5" EPS this way for twelve (delivered) dollars a sheet. I figure I am at about R10 or so (correct me if I am wrong) for my "outsulation." I also intend on using the same stuff in the basement with an R5 or R6 one inch Polyiso foil foam over it, with crisis crossed and taped seams. The same vendor has a multitude of Polyiso foam. So I think I will get to about R16 on my basement walls for about 75-85 cents a SF.

4. 
   Bill_NC | May 14, 2016 09:56am | #4

   Martin, Charlie, and Joe:

   Thank you for your feedback.

   Most of the commercial lumber yards here only stock 1/2" sheets of foam.

   I did find the NGBS Green Certification below for the Kingspan.

   I was able to buy the 3/4 Kingspan XPS for $13.57 a sheet.

   HAVE BEEN CERTIFIED FOR POINTS TOWARD NGBS GREEN CERTIFICATION TO THE ICC 700 NATIONAL GREEN BUILDING STANDARD AS DETAILED IN NGBS GREEN CERTIFIED PRODUCT REPORT #NGBSGCP-00136.

   http://www.trustgreenguard.com/wp-content/uploads/2015/09/KINGSPAN-GreenGuard-Poly-Insulation-Board-2015-2016.pdf