The white board is crumbly, especially the cheap foil coated stuff that HD sells right now. It's hateful to work with.
Blue and pink boards do have some of the disadvantages Vinay mentioned. But, they are far superior at rejecting moisture. Dow themselves has a paper on it. I need to find it again. Now, there is a 2" thick pink board I saw locally at Albuquerque HD locations. It was the only one available. I believe it was Owens Corning Foamular 150. Comes in many different densities. But, inside ferrocement? Doug Lacy uses plain blue board. See his pics. I believe every other concrete application would use them too. Superior waterproof performance (no reduction in R value over the long term). Outgassing? I dunno. Read this page that lists all types: http://bit.ly/rmNjxN "Polyurethane and polyisocyanurate are both closed-cell foams. They contain low-conductivity gases in the cells (usually one of the HCFC or CFC gases.) The higher R-Values (R 7.0 to 8.0) are the result of thermal resistance of the gases in the cells. This can lead to a couple of disadvantages including: off gassing of HCFC or CFC gases, and reduced R Value over time as the gas escapes." They say foil foam board (Thermax etc) are the ones that outgas. And the gas escapes, leading to the R Value loss. Here is the MSDS for *all* pink boards from OwensCorning: http://bit.ly/qg1qDl MSDS for Super Tuff-R: http://bit.ly/ny2oHQ The hydrocarbon blowing agent for Dow Super Tuff-R is a "trade secret" (read MSDS). So we don't know *what* it is or *what* is in it at all. I'd like to see actual outgas hard data for the pink and blue boards. As in, a document on it. On Aug 2, 7:07 pm, "ken winston caine" <k...@mindbodyspiritjournal.com> wrote: > Couple questions: > > 1. Please remind me of why (other than environmental toxicity and > flammability) early on you rejected using the 2" thick white (EPS) > polystyrene foam boards in favor of the polyiso foamboards? > > 2. If your only choices -- as are mine locally -- are between EPS and XPS, > which would you choose and why? (As > inhttp://www.homedepot.com/h_d1/N-5yc1v/R-202090328/h_d2/ProductDisplay... > vs.http://www.homedepot.com/h_d1/N-5yc1v/R-100320352/h_d2/ProductDisplay..., > for instance. > > 3. Was an argument against EPS its lack of rigidity? > > 3. Was it water permeability? I understand that the EPS styro sops it up > (and loses insulating ability in the process) and that XPS doesn't. > > 4. If you were going to throw up a quickie small building and would be > encasing the foam boards in fidobe papercrete and a fibrous-cement-like > shell in and out, would you still rule out the less expensive white styro > boards for the initial building? Or would you forgo foam altogether? > > Thanks, > ken winston caine -- You received this message because you are subscribed to the Google Groups "hexayurt" group. To post to this group, send email to hexayurt@googlegroups.com. To unsubscribe from this group, send email to hexayurt+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/hexayurt?hl=en.
