Many people we trust are quickly coming to the conclusion that all use of closed cell spray foam, XPS and other extruded foam insulations in the construction industry needs to stop, right now. Not later and not maybe.
This is especially true when you consider that we have such easily available, less damaging foams stocked in every store. EPS, poly-iso and water blown foams are better by enormous factors if you must use foam. Far better again are mineral wool and cellulose.
Alex Wilson’s report at GBA is crucial reading for everyone in the construction industry:
http://www.greenbuildingadvisor.com/blogs/dept/energy-solutions/avoiding…
It’s really easy to get people upset about possible health hazards in their homes, especially if we glibly reassure them there are no risks to certain products whether we know that to be true or not. In building, as in any other endeavor, it’s easy to convince ourselves something is true if we really want it to be true. I don’t know how safe spray foams are. I do know they’re used a lot, and I also know that the quality and safety control within the industry is (at least in my market area) VERY uneven. I also know that there’s rampant confusion regarding what building codes really require for thermal and ignition protection; that what sales reps say often contradicts what their own literature says with regard to ASTM testing among other things; and that, of all the newly prevalent products we use to make homes perform better, spray foams worry me the most in terms of potential liabilities.
The claim that closed-cell spray urethane foam meets the requirement that you call “reversibility” – the ability of a thermal envelope to be able to dry in either direction – is simply false. Like any vapor barrier, 2 pcf foam prevents drying. If there is a relatively impermeable material on the other side of the assembly (such as self-adhering membranes on walls or roofs) then the sandwiched wood sheathing cannot dry if it ever gets wetted by an imperfection in the weather barrier any time in the life of the building.
Additionally, because it is hydrophobic, any water leakage will be fully absorbed by wood framing and sheathing materials, increasing their saturation and the probability of mold or rot. Making an assembly impermeable to both liquid and vaporous moisture is a valid strategy only in a perfect world in which nothing ever leaks.
In the real world, some vapor permeance is essential to the long-term durability and livability of a house. And in mixed climates (most of the US), where the seasonal moisture drives reverse, it is important for a thermal envelope to be able to dry in both directions.
Closed-cell spray foam fails this requirement.
To sum up the partial list of negatives:
It’s so toxic to install that humans need full skin isolation and protection from the chemical components. Over exposure to isocyanurates can lead to devastating chemical sensitivities, including permanent respiratory damage (Direct from Bayer, a major manufacturer: http://www.greenbuildercollege.com/studyguides/BaySystemsSprayInsulation…).
During installation, if the chemicals are not mixed correctly or at the proper temperature you can get incomplete curing of the two chemical components, either of which is toxic on its own. This is a very rare situation, thankfully, but this rare risk is still one I wouldn’t ever recommend one of our clients take with their house.
And, once applied (correctly or incorrectly) a house is bound up and glued together in a manner that is impossible to reverse, limiting the ease of future renovations drastically, even simple actions like adding wiring or fixing plumbing issues.
It does nothing for thermal bridging at typical supplied depths, wood framed buildings still end up with an ~R-6 insulation gap every 16″ at each wood stud.
Polyurethane is best used in a cool, dry environment. A good design will ensure its protection from extremes in temperature and from becoming wet. It will also keep the foam dry by providing a vapour barrier that
will keep excessive moisture from entering the material and condensing or freezing in the colder parts of the foam. Polyurethane does not have good freeze-thaw resistance. If the material is wet and is subjected to
freeze-thaw cycles it may disintegrate after only a few dozen cycles.
And worst of all, it’s extremely expensive, far worse than other comparable insulation materials…
But, none of these specific technical issues gets at your main point, which is consumer confusion, because every point I have listed will be eagerly refuted by the closed cell spray foam industry, which has more lobbying money available than I have time to type.
And this is where we need to get to work changing these larger systems. It’s why I think we can’t shy away from pushing for policy changes, more than trying for individual behavioral change.
There are viable substitutes for all these blowing agents available, this is a US regulatory problem at heart.
Links FYI
http://www.thomasnet.com/articles/plastics-rubber/foam-insulation-danger
Got Bad Air 