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Community and Q&A

Protecting Building Shell From Condensation

potton | Posted in General Questions on

Our house in zone 6 has its shell closed and is insulated but the wall’s interior vapor retarder (Intello Plus) will not be installed before spring, and will remain unoccupied…
What are our options to reduce/control the amount of condensation inside the cavity during the next months?  Constantly run one (or two) dehumidifier and lower the temperature (say to 50F/10C)?

[Its current state of is Typar /1,5 in of low density fiberboard/ R20 of hemp batts between 2×6 studs. 
The floor is concrete pourred Oct 26, hydronic heating in function; the ceiling is a cathedral with R60 cellulose and foil-faced fiberboard; triple-pane windows]

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  1. Expert Member
    NICK KEENAN | | #1

    I'm going to say you're probably OK if you keep the interior at 50F. Air that cold can't hold a whole lot of moisture, and the general consensus is that mold isn't a problem until temperatures get above 60F. It sounds like your walls are pretty vapor-open to the outside and any moisture that gets into the walls will be able to escape. The one part I'd worry about is the roof, which doesn't sound vapor-open to the exterior. However, even in winter if the sun beats down the roof will easily heat up warmer than the interior and you'll get vapor drive toward the interior, which should dry things out.

    1. potton | | #3

      Well the roof is a ventilated single slope, with a 12in air channel above R60; the foil facing vapor barrier is on the ceiling side all taped at this point.

  2. seabornman | | #2

    I had a house in zone 5 that had exposed wall insulation through a winter. I could stick my hand through the insulation and feel heavy frost on the back of the sheathing at the end of winter. It all evaporated and was dry by the time the vapor retarder and drywall was installed the next summer.

    1. potton | | #4

      Thanks for the feedback!

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