Replies

1. GBA Editor
   Martin Holladay | May 31, 2013 11:00am | #1

   Mike,
   There are at least three issues here:

   1. Is there a legal definition of offgassing?

   2. How much pentane (the blowing agent used for polyiso) is released per day per square foot of polyiso?

   3. Are the blowing agents in the insulations you are worried about -- pentane in the case of polyiso -- dangerous to humans in the concentrations at which they are likely to be encountered?

   I don't know if there is a legal definition of offgassing. Almost everything offgasses, including a fresh loaf of bread, an apple pie, and a new pair of sneakers.

2. Expert Member
   Dana Dorsett | May 31, 2013 11:56am | #2

   Foam insulations offgas things other than the blowing agents, and at different rates. Polystyrene (EPS and XPS) has significant amounts of styrene offgassing early in life.

   Polyurethane and polyisocyanate both release polyols and isocyanates during blowing, but the rates diminish rapidly over time as the product cures, provided they dialed in the temps & chemical mix correctly. But the amount & rate of release are affected heavily by the mix and chemical temperature(s) during installation. An improper mix can lead to very long term outgassing. The HFC blowing agents used for closed cell polyurethane are released at a much slower rate (give it a half-century or more) than the pentane used for polyiso (weeks, months/years/decades, depending on the thickness & density of the foam, and the type of facers used.) The initial R-values of pentane blown polyiso are well above the labeled values, but most will hit the labeled value in well under a decade, which means most of the pentane has already found it's way out. With EPS it pretty much hits it's labeled value in mere months, if that.

   Pentane has a sugary sort of smell that you can sometimes detect when cutting freshly blown iso or EPS, but it's pretty faint (if you can smell it at all) when cutting foam that's even a year old. I've read (but not seen formal data) that the half-life of pentane in EPS sheet goods is measured in days, but with foil facers it goes up dramatically. I assume that's also true for polyiso, which has a less-well defined closed cell structure than mid or high density EPS.

   There's reason to be skeptical of polyurethane kit vendors's claims about outgassing since the foam kits and throwaway kit blowing guns do not have the temperature & mixture controls of professional foam blowing equipment. Somewhere there is probably some fine print about the exact temperatures and mixtures where the outgassing rates fall below some industry or safety agency max level, but there's no guarantee a kit user would always (or ever?) be able to meet those specs.

   (Almost) full disclosure: About fifteen years ago I designed the control & power electronics for temperature controls on a professional polyurethane blowing system. (I was operating as a contractor and I'm not at liberty to divulge the name of the client, due to contractual non-disclosure clauses. As part of the prototype testing I got to see some pretty sticky messes when the temps were intentionally set way off for test purposes, and many months later the samples still smelled. It's possible to really screw it up if you try hard enough, and I'm betting the lingering stink wasn't the blowing agent, but a primary chemical.

3. 
   user-1091831 | May 31, 2013 12:04pm | #3

   Hi Martin,

   You make good points there. With that in mind, I would venture to guess that the company advertises as "no offgassing" from the perspective of item number 3. If the rate of offgassing hasn't been proven to be concentrated enough to pose any noticeable health effects, and if people's main concern with offgassing is health, then why not advertise it as free from offgassing so they can add another bullet point advantage to the product?

4. 
   user-1091831 | May 31, 2013 12:09pm | #4

   Dana,

   Thanks for that detailed insight, much appreciated!