Exterior insulation vs. rainscreen
We are building a single family home in zone 2 in Marin County and trying to decide whether to have a rain screen or exterior insulation. For some reason our building department will not allow us to do both, they say since we are in a high fire zone (WUI) we can not have insulation between the furring of a rain screen and wall sheathing.
In any case, we have 2×6 walls with blown in Fiberglass that should have R value of R23.
If we were to choose between either rain screen or R6 of exterior insulation which would be recommended?
From what I can find reading online both can be omitted in our climate zone 2 in Marin County CA, but not sure if there is a economic/building science case to install them anyway.
To me it seems that a rain screen might be the better choice given it would be less expensive and possibly extend the life of our siding, less maintenance, increased drying, less chance of water issues migration into wall assembly. These are general benefits but don’t know how to evaluate to my particular climate.
The exterior insulation may not be as crucial as we don’t need to worry as much about condensation in our wall assembly in our climate, and we have R23 already in our wall, with thermal bridging might have a real R value close to R20 which seems good enough in our climate. And our contractor who hasn’t done it before thinks it will be expensive to install.
Am I thinking about this correctly?
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