Exterior Peel and Stick Membrane on ABOVE grade ICF Walls
I’m building an all ICF home in Climate Zone 5. We’re planning to use the manufacturer recommended peel and stick waterproofing membrane before grade. For the above grade walls, we’re also planning to install a weather resistive barrier to prevent bulk water intrusion – I’m aware of the debate about whether or not this is necessary and have decided that since there’s any debate about it, I’m just going to install one for peace of mind. The ICF block manufacturer doesn’t require an above grade wrb, however, they say that if you want to use one or if it’s required by code, they recommend using tyvek or similar. We’re using horizontal strapping with vertical vinyl siding as our cladding.
I’m thinking about using a non-breathable steep roof underlayment peel and stick membrane instead and I’m just wondering if there are any durability risks to installing something non breathable like that on the above grade exterior walls. I’m not looking to get into a debate about whether this is a waste of money, the extra cost is worth it to me for ease of installation, skipping hundreds of penetrations to hold building paper up, etc. I’m just concerned about any problems with the walls not being able to breathe out dry to the exterior (we will have latex painted drywall on the interior). I asked the ICF manufacturer rep and he said “it should be fine”, but I was hoping for a little more reassurance. Obviously this would be bad for a wood framed wall, but I would think that the EPS foam and concrete shouldn’t be harmed by whatever water vapor might enter the walls from the interior – I don’t think it would be good for them to be soaked, but if they somehow got a little moisture and had to dry to the interior through the foam and drywall I wouldn’t expect any issues.
Am I missing anything? Can anybody think of any problems with waterproofing it this way (other than it possibly being unnecessary or overkill)?
Thanks in advance.
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