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Insulate under floor

  • 13-10-2014 9:09am
    #1
    garlad
    Registered Users, Registered Users 2 Posts: 601 ✭✭✭


    Hi,
    Recently had a new boiler installed in the playroom (old garage). Carpet is up.
    I have taken up most of the subfloor ply.
    I hope to insulate between the joists with something like rockwool, lay new subfloor and laminate over this.
    There is a gap below the bottom of the joists, from about 12 inches at the back of the room, to 4 inches at the front.
    Can I just fill the whole cavity, or do I need to just fill between the joists and somehow do something to hold up the insulate?
    I read somewhere that you should leave a gap below to allow the joists to breathe, but it would be much easier to just pack the whole thing.
    Thanks


Comments

  • #2
    whizbang
    Registered Users, Registered Users 2 Posts: 1,974 ✭✭✭whizbang


    No Issue if you are using rockwool or similar.

    If you were using rigid foam insulation, then you should leave a gap.


  • #3
    garlad
    Registered Users, Registered Users 2 Posts: 601 ✭✭✭garlad


    Really, so no danger of rot or anything?
    All videos I have seen on youtube show them leaving a gap, although in most of the videos I watched on youtube the crawl space is much deeper and would cost a fortune to fill with wool.


  • #4
    Chalkitdowndiy
    Registered Users, Registered Users 2 Posts: 28 ✭Chalkitdowndiy


    Just surprised that you'd have a boiler in a playroom or a garage.

    ChalkItDown :)


  • #5
    garlad
    Registered Users, Registered Users 2 Posts: 601 ✭✭✭garlad


    Chalkitdowndiy wrote: »
    Just surprised that you'd have a boiler in a playroom or a garage.

    ChalkItDown :)

    Why's that?


  • #6
    Chalkitdowndiy
    Registered Users, Registered Users 2 Posts: 28 ✭Chalkitdowndiy


    Well, if it's an oil fired boiler, for example, I thought they were best sited outdoors - that's all. Just from a health and safety perspective.

    ChalkItDown :)


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  • #7
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,146 Mod ✭✭✭✭BryanF


    garlad wrote: »
    Hi,
    Recently had a new boiler installed in the playroom (old garage). Carpet is up.
    I have taken up most of the subfloor ply.
    I hope to insulate between the joists with something like rockwool, lay new subfloor and laminate over this.
    There is a gap below the bottom of the joists, from about 12 inches at the back of the room, to 4 inches at the front.
    Can I just fill the whole cavity, or do I need to just fill between the joists and somehow do something to hold up the insulate?
    I read somewhere that you should leave a gap below to allow the joists to breathe, but it would be much easier to just pack the whole thing.
    Thanks
    Leave a gap. Place mesh or fleece between the joists to hold mineral wool insulation, then place sheet of plastic over top of the joists and tape/seal the joints to stop air-movement / passage of moisture.
    garlad wrote: »
    Really, so no danger of rot or anything?
    All videos I have seen on youtube show them leaving a gap, although in most of the videos I watched on youtube the crawl space is much deeper and would cost a fortune to fill with wool.
    your right to be concerned. There should be some form of vent blocks or similar visible on the outside of your house venting the subfloor. The gap below the joists should be kept clear to allow air circulation


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