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    bobfeather's Avatar
    bobfeather Posts: 1, Reputation: 1
    New Member
    		  
    #1

    Apr 25, 2010, 06:16 AM
    wondering about the best way to insulate under a deck
    would like to insulate under a deck 2x8 joists the deck has been converted to a sun room / living space vapour barrier or no ? Batt insulation ? Talked to a guy about spray foam but he wants big $$$ lots of room to get under it thanks
    bob
    hkstroud's Avatar
    hkstroud Posts: 11,929, Reputation: 899
    Home Improvement & Construction Expert
    		  
    #2

    Apr 25, 2010, 08:14 AM

    Install batt insulation supported with wire rods for support, moisture barrier to warm side (floor). Install plywood sheathing to bottom edge of joist.
    KBC's Avatar
    KBC Posts: 2,550, Reputation: 487
    Ultra Member
    		  
    #3

    Apr 25, 2010, 08:32 AM
    I have crawled in crawlspaces you couldn't breath heavy in to insulate under places.. You can do anything you want.

    I used solid insulation for most of my personal projects including this,the house and shop both have upwards of 4 inches of solid polyisocyanurate insulation(R-7 per inch)

    Being a solid board and that you have space to work with,this would be the type I would suggest.

    Installing the boards then applying strips of wood to each edge of the floor joists left exposed would keep them tight to the floor.A vapor barrier would be a good idea as well.

    Hope this helps you.
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    manhattan42's Avatar
    manhattan42 Posts: 143, Reputation: 11
    Junior Member
    		  
    #4

    Apr 26, 2010, 12:21 AM

    Whether you need a vapour retarder and where it should be located depends upon where you live.

    For colder climates, the vapour retarder needs to go on the warm-in-winter side.

    For southern warm and moist climates, no vapour retarder should be installed or it should be installed on the outermost side of the floor assembly.
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