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Exterior Insulation R-Value in Mixed-Humid Climate

Brad17 | Posted in General Questions on

Hi,
We are designing a wall assembly for a new home in Suffolk County, NY, which is a mixed humid climate (4A). One option we are considering is:
2×6 wall with R23 Rockwool batt cavity insulation
zip sheathing
rain screen or cedar-breather
cedar shingles

Two questions:
1) to avoid a wet wall, what R value should our continuous exterior insulation be for this zone (4A)?
2) Would something like Intello Plus on the interior be wise here?

thanks!
B

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Replies

  1. PAUL KUENN | | #1

    All you need per code is R3.75 in zone 4. check out:
    https://www.greenbuildingadvisor.com/article/calculating-the-minimum-thickness-of-rigid-foam-sheathing
    You get R4 with 1" of EPS which has more permiability than other board insulations for some exterior drying.

  2. Brad17 | | #2

    Thanks, Paul! Very helpful.

  3. PAUL KUENN | | #3

    You can get used EPS pretty cheaply but many are using the more expensive mineral wool which does add good fire protection.

  4. Brad17 | | #4

    Thanks. And the "A" aspect of Zone 4A doesn't impact the way we think about exterior insulation at all?

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