Termites vs underslab insulation
Hey GBA. I’m working on a project in CZ 5A in a moderate to heavy termite area and looking at solutions for insulating a raft slab.
1. I’m planning on using Stego Pango Wrap 15 mil vapor barrier for its termite protection under the slab. It’s quite expensive. Does anyone know a lower cost alternative?
2. How much do we need to worry about termites eating the sub slab insulation? I’ve been getting the impression it’s difficult to get hold of treated EPS /XPS.
3. Since Pango Wrap is a termite barrier, could it work to just lay that over the crushed stone base, lay the foam insulation over that with seams taped, then pour the slab? Choosing an optimal tape for the seams would be wise. T&G XPS would provide strongest insulation seams and least permeability of any options I can think of to keep bleed water out.
I considered Rockwool Comfortboard 110 below the slab, but availability doesn’t look good recently, and being a structural raft slab I don’t think the compressive strength is high enough.
Any better ideas here?
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Replies
I wonder? Would a foot or so of small diameter washed
gravel (under the insulation) prove to be an effective
termite barrier - does anybody know??
If the rocks provide a dry area, it will help to limit termite activity. Termites need the moisture, so if you can do something to keep an area dry, that will help to keep the termites from crossing. The same thing works for ticks outdoors on the surface -- they don't like to cross dry areas (usually crushed stone), because it causes them to dry out and die.
Termites won't "eat" foam, but they can burrow in it. Termites actually eat the wood, the wood is their food source. You might be able to find a paint-on borate product that would work as termite protection underground, but I've never tried that. The idea would be to coat the foam with a borate treatment to essentially create your own "treated" foam product to use. I can't say how effective that would be over time though -- the borate coating might degrade over time and wash away or otherwise lose effectiveness.
Bill
Maybe foil faced R-Tech EPS would be a good choice for the insulation:
"R-TECH is manufactured with an inert additive that deters termites and carpenter ants. R-TECH does not sustain mold and mildew growth."
The commonly stocked "I" variant is only 13 PSI compressive strength, which I don't love with a raft slab, but it's only a single storey building with wood frame walls.