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Exterior insulation

Kaihomes | Posted in Energy Efficiency and Durability on

The thickness of exterior insulation. Will r3 do anything in for a house built in Connecticut.
interior walls will be cellulose.

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  1. Expert Member
    Dana Dorsett | | #1

    >"Will r3 do anything in for a house built in Connecticut."

    Yes, it will do something. But R3 is not sufficient for dew point control without class-II vapor retarders, and has some potential risks.

    All of Connecticut is in US climate zone 5. For a 2x6 framed house with R20-ish cellulose it takes R7.5 on the exterior to provide sufficient dew point control without interior vapor retarder to keep the sheathing and insulation dry over a full winter. For a 2x4 / R13 cellulose wall it takes at least R5 for dew point control (and to even meet IRC code minimum thermal performance.)

  2. Jon_R | | #2

    Warmer wood sheathing is helpful and give the distribution of temperatures, more than you would think. On the other hand, low exterior perms (eg, foil faced as compared to unfaced EPS) is a negative.

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