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Air tightness layer & Wind tightness layer: whats the difference ?

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  • 25-04-2015 11:26am
    #1
    Calahonda52
    Registered Users Posts: 12,235 ✭✭✭✭


    I think I know the answer but am having a "discussion" with a builder about it.

    I won't share his ideas here, just wondering can someone pen a few lines on the difference that I can use rather than just tell him what I want and tell him either do it or .....
    Thanks

    “I can’t pay my staff or mortgage with instagram likes”.



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    #2
    Strolling Bones
    Registered Users Posts: 615 ✭✭✭Strolling Bones


    air tightness measures tend to take place on the warm side of the insulation layer.
    wind tightness - to the cold side


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    #3
    Calahonda52
    Registered Users Posts: 12,235 ✭✭✭✭Calahonda52


    Thanks.
    Its a bit unusual as the insulated structure is inside a rain-screen which is ventilated top and bottom.
    There is a walkway between the rain-screen and the insulated structure.

    Makeup of insulated structure, from inside, is 18mm mdf, painted, screwed onto 100 mm deep metal stud partition, which is insulated, between the studs with 100 mm alu covered, on both sides, rigid "poly" insulation.
    All joints taped and taped over the studs from the walkway.

    Builder's view is that the painted mdf and the taped alu covered insulation is good enough for the air-tightness and the rain-screen does for wind-tightness so no need for any "expensive" membranes

    “I can’t pay my staff or mortgage with instagram likes”.



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    #4
    BryanF
    Moderators, Home & Garden Moderators Posts: 10,140 Mod ✭✭✭✭BryanF


    Calahonda52 wrote: »
    Thanks.
    Its a bit unusual as the insulated structure is inside a rain-screen which is ventilated top and bottom.
    There is a walkway between the rain-screen and the insulated structure.

    Makeup of insulated structure, from inside, is 18mm mdf, painted, screwed onto 100 mm deep metal stud partition, which is insulated, between the studs with 100 mm alu covered, on both sides, rigid "poly" insulation.
    All joints taped and taped over the studs from the walkway.

    Builder's view is that the painted mdf and the taped alu covered insulation is good enough for the air-tightness and the rain-screen does for wind-tightness so no need for any "expensive" membranes
    set your required air-tightness level, get a tester of your choosing to test before the builder has closed anything up. What had your arch shown in the detailing? Is mdf on inside? Is it adequate to act as a vapour control layer aswell as AT layer?


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    #5
    Strolling Bones
    Registered Users Posts: 615 ✭✭✭Strolling Bones


    Calahonda52 wrote: »
    Makeup of insulated structure, from inside, is 18mm mdf, painted, screwed onto 100 mm deep metal stud partition,

    No vapour check?

    Calahonda52 wrote: »
    Makeup of insulated structure, 100 mm deep metal stud partition, which is insulated, between the studs

    Straight trough repeating thermal bridge. Really really bad.

    Calahonda52 wrote: »
    with 100 mm alu covered, on both sides, rigid "poly" insulation.
    All joints taped and taped over the studs from the walkway.

    How durable is that ? Tapes and inslaution will degrade with passing traffic.


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    #6
    Calahonda52
    Registered Users Posts: 12,235 ✭✭✭✭Calahonda52


    SB, Thanks
    No vapour check and two out of two for the others!

    “I can’t pay my staff or mortgage with instagram likes”.



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