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Roof Insulation

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  • 16-04-2012 12:28pm
    #1
    Pat2
    Registered Users Posts: 11 ✭


    Hi

    First time poster so hopefully I make sense in what Im saying. Im building a new house at present & Im looking into different types of roof insulation. Its a dormer/story & half house. Im trying to get it as airtight as possible. I want to insulate from the wall plate to the ridge as I have only a small attic area. I am considering the following 2 options
    1. Putting spray foam between the rafters from the wall plate to the ridge & putting an insulated plaster board on top of it. The crowd that supply this said I can apply the foam direct to the breathable felt & there is no need for any plastic between the plasterboard & the sprayfoam. I do not have my roof counter battened.
    2. The other option I was considering is putting insulated boards between the rafters myself & covering all the rafters with an airtight membrane & then putting an insulated plasterboard on top.

      Which way do ye think is best or is there any better way?
    What do ye think of the installer stating that the foam can be applied direct to the breathable felt?

    Thanks in Advance


Comments

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    #2
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    read the cert on the foam, it wont suggest this approach..
    And is it a good idea to try to fit a rigid unbreathable insulate between timber joists?

    My prefered spec (with some varition depending on roof shape) : slate, Double battens, Breathable felt, I-joists, cellulose between, taped osb board, service cavity / plaster board finish. Maybe timber insulate board instead of felt and membrane instead of osb


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    #3
    barfold
    Registered Users Posts: 28 ✭barfold


    I am a carpenter and would not agree with applying foam directly to felt either.Personally I would use rigid board between rafters with 50mm air gap to felt flush to inside of rafter, then 50mm rigid board on underside of rafters, tape all joints then batten over for services and plasterboard.


  • Options
    #4
    derealbadger
    Registered Users Posts: 1,101 ✭✭✭derealbadger


    Pat2 wrote: »
    Hi

    First time poster so hopefully I make sense in what Im saying. Im building a new house at present & Im looking into different types of roof insulation. Its a dormer/story & half house. Im trying to get it as airtight as possible. I want to insulate from the wall plate to the ridge as I have only a small attic area. I am considering the following 2 options
    1. Putting spray foam between the rafters from the wall plate to the ridge & putting an insulated plaster board on top of it. The crowd that supply this said I can apply the foam direct to the breathable felt & there is no need for any plastic between the plasterboard & the sprayfoam. I do not have my roof counter battened.
    2. The other option I was considering is putting insulated boards between the rafters myself & covering all the rafters with an airtight membrane & then putting an insulated plasterboard on top.

      Which way do ye think is best or is there any better way?
    What do ye think of the installer stating that the foam can be applied direct to the breathable felt?

    Thanks in Advance

    there are 3 foams certified for use in Ireland by N.S.A.I all of them must be fitted with a spacer card if you spray onto the felt the job is not certifiable regardless of weather the foam used is certified or not


  • Options
    #5
    1865
    Registered Users Posts: 101 ✭✭1865


    Have you considered a warm roof? you put the insulation on top of the rafters and the tiles on top of the insulation. That way there is no thermal bridge with the wood.

    Just a thought.


  • Options
    #6
    Pat2
    Registered Users Posts: 11 ✭Pat2


    Thanks for all the replies.

    My roof is already constructed so I cannot put any insulation on top of the rafters. My felt, battens slates are all on.


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    #7
    nutandbolt
    Registered Users Posts: 8 ✭nutandbolt


    Hi all,
    We are almost ready to insulate our roof. We have narrowed it down to two types of insulation. Just wondering if anyone has any opinions on Metac or MetStud??
    Thanks


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    #8
    Curious Geroge
    Registered Users Posts: 1,013 ✭✭✭Curious Geroge


    nutandbolt wrote: »
    Hi all,
    We are almost ready to insulate our roof. We have narrowed it down to two types of insulation. Just wondering if anyone has any opinions on Metac or MetStud??
    Thanks
    Metac


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