Exterior Wood-Fiber Insulation Cons
I was pretty set on using unfaced EPS for exterior insulation given the price, cold temp r value, and permeability but I just learned a local insulation contractor is importing wood fiber insulation from Europe. He gets entire shopping containers at once and handles all the importation so apparently the price is significantly more competitive than you see at 475 supply or otherwise. It looks like an all around awesome product with no negatives. What am I missing?
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I'll be interested to hear the discussion around this. It sure seems like the only downsides are price and availability. If you have those solved...
What is wood fiber insulation's resilience to water that might make it past the WRB? Will it drain water and dry or hold it and rot/expand, thereby requiring a near flawless WRB installation? Another similarly carbon-negative external insulation option is cork, which is pretty resilient to water - although it still probably needs an air gap so it can dry.
It has paraffin wax added to make it hydrophobic. I think that along with a rain screen will make it a long lasting material.
There are many advantages to rigid wood fiber insulation but a few downsides: not insect-resistant (but neither is most foam), not fire-resistant (but neither is some foam), not rot-proof. It typically has paraffin added for moisture resistance so as long as you have good water management details including a rain screen that allows for drainage you shouldn't have to worry about water. It's usually tongue-and-groove and can be used as a WRB, though it's safer to use a separate WRB to resist wind-blown water. It's vapor-open and allows drying. There are ways to address the downsides if they are important to you.
There’s some YouTube videos showing significantly better fire resistance than foam which is good. Obviously not as good as mineral wool. Luckily I’m located where termites are not an issue, I could see that being a major issue for most of the country.
Most homes in the US are made of wood, the same material with the same lack of resistance to termites. Termite shields can help identify an infestation and you can add things like a rock course around the house and keep plantings away from the house to deter them, but unfortunately poison is usually part of the solution when it comes to termites.