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    light house's Avatar
    light house Posts: 4, Reputation: 1
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    #1

    May 9, 2009, 12:28 PM
    cathedral ceilings
    What is the correct way to insulate and vent a new cathedral ceiling? The ceiling/roof is made up of 2x10, 16" o.c.

    Sincerely,
    light house
    21boat's Avatar
    21boat Posts: 2,441, Reputation: 212
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    #2

    May 9, 2009, 02:53 PM

    The best way to insulate it is with spray Foam

    Note: If fiberglass insulation gets 5% of moisture in it it looses 95% of its insul properties.

    Two major things go wrong with a cathedral ceiling is 1. not enough rafter thickness to obtain the proper (R) value for its Geo. 2. Is the venting from the soffit to full ridge vent is not addressed well to keep the min 2" air space in each rafter bay to stop moisture build. 3. Moisture barrier is so crucial in close applications on cathedral and if that was not used then again moisture.

    Hear is a Geo map for (R) values. If you need (R) 30 then the rafter solidi be a 2x12 for 91/4" insulation and the air space full rafter width in each joist bay.

    http://www1.eere.energy.gov/consumer...nsulation.html

    http://insulationinfo.org/insulation...ation-r-value/
    creahands's Avatar
    creahands Posts: 2,854, Reputation: 195
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    #3

    May 10, 2009, 07:12 PM

    Install air baffles between rafters to allow air flow from soffit to ridge vent.the baffles will not let insulation to touch roof sheathing.

    Good luck

    Chuck
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