Revisit of 2016 discussion of rodents, insects & rigid foam
These alerts/discussions in 2016 left me rather discouraged:
https://www.greenbuildingadvisor.com/article/if-ants-like-rigid-foam-should-we-stop-using-it
https://www.greenbuildingadvisor.com/article/foamglas-exits-u-s-residential-market#0
I checked and Foamglas has not returned to the US residential marketplace. My takeaway from the other article was that Rockwool Comfortboard provided the best solution for insect/rodent protection in load-bearing insulation in particular, and external perimeter insulation in general. Has anything new, like the Halo Subterra Plus, displaced Comfortboard as our best option to prevent serious structural damage from pests tunneling through insulation?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Gshps4all,
Unfortunately I have no good answers. For that it's worth, here's where I'm at now.
On my own house, and those of my clients living in vulnerable environments, I suggest setting up a perimeter of impervious materials around the foundation, and not having any points at which the soft landscaping comes within several feet of the house. That coupled with periodic spraying should ensure colonies aren't able to get established in the foam, walls or roof cavities.
That's not a great strategy as it relies on constant diligence, which isn't something we can expect most people to maintain over extended periods of time.
Would I use exterior foam, or foam under load-bearing portions of the house here? No chance.
Our inability to access Foamglas in the US for residential applications is driving me nuts as it sounds like an ideal product for green construction. The same product is sold here for the commercial building industry. Because Owens Corning is no longer marketing it to the residential marketplace, does that mean that a building inspector will not allow one to use the commercial building version on a residential building even though it is perfectly appropriate, or is it a matter of having difficulty finding a contractor or architect with an Owens Corning industrial account who could order a small enough quantity for a single residential house?
For perimeter insulation, I’ve been reading up on the FoundationPRO system. It has a hard shell surrounding GPS foam to serve both as a protective layer and a decent aesthetic if parts of the insulation will be left exposed above grade.
https://www.progressivefoam.com/product/foundation-pro/amp/
The FoundationPRO product looks interesting. Do you know how the price compares against Foamglas? The GPS would be cheaper, but the finished assembly might be comparable in cost, and the Foamglas has better intrinsic properties with respect to animal, moisture, and fire resistance, as well as greener source materials.
that looks cool, if you continue with some other kind of foam below grade isn't that part also susceptible to insects tho, or do they only operate a certain level down?
One component of a solution might be foamed glass gravel substitute such as "glavel". https://www.greenbuildingadvisor.com/article/foam-glass-plant-to-open-in-vermont
It's not great insulation, but below grade you are not restricted in how much thickness you can use, so you can get whatever R-value you want. The challenge is then above grade. According to a comment in the link above, the pictured installation uses "glapor" boards which are the equivalent of foamglas, but from recycled glass, make in Germany, and imported by Glavel. But I can't find anything on the Glavel site. Here's the Glapor site:
https://www.glapor.de/en/produkte/cellular-glass-boards/
Here's a Canadian importer/distributor that carries Glapor Boards:
https://onlinestore.performancehaus.ca/Product/Details/Mp232/Glapor-Foam-Glass-Boards
Charlie, great to see the Glapor products moving into the US, although frustrating that the boards are not available, and the glavel is cost-optimized only for delivery within a 300-mile radius of the Vermont factory. The R values for the highest strength Glapor and Foamglas sheets are the same. The R value of the Foamglas increases as the compression strength decreases. The Glapor doesn't claim an increase, but I assume the physics are the same for the two products.
So the boards would be placed on the outside of the foundation and the glavel under the slab.
I am going to walk out on a limb here. At least in the case of floating slabs, I am wondering what function a concrete slab performs that a Foamglas or Glapor panel slab could not do better? Despite being constructed from tiles, Foamglas claims that a two-layer Foamglas slab using waterproof adhesive would be moisture proof, fireproof, insulating, and critter proof. The glass slab would not be as strong as concrete, but it would be strong enough to support the load requirements of the subfloor above it. I understand that the CO2 produced during the Foamglas production is about a dozen times lower than that of the cement in concrete. A concrete slab has to be at least 4" thick to isolate its embedded steel from the atmosphere. A glass slab could be thinner and would not require a moisture barrier, so the costs might be comparable. The glass slab would not get stained or absorb oil and its properties would not change over time. The glass tiles could be installed at any temperature and would not require the week-long curing process during which concrete must be kept moist and warm for optimal strength and long-term durability. The only potential gotcha I can think of for the glass tiles might be their reliance on an adhesive to maintain the continuous moisture/critter barrier, but it sounds like, for Foamglas at least, they can point to decades of experience in using such adhesives with their product.