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  1. #1
    Join Date
    Jul 2010
    Posts
    6

    Default Adding Insulation with trussed roof?

    I already purchased enough insulation to insulate my garage ceiling in two layers. My roof is constructed with 2x4 trusses
    16" on center.

    I am starting to install 3 1/2" rolled insulation between the bottom truss cords which will get me level with the tops of the truss cords. Vapor barrior facing the inside of the garage.

    My next step is to add the additional insulation without a vapor barrior on top of that. Normally I would place the second layer of insulation at right angles to the first layer. If I install the second insulation layer at right angles I will be bumping up against the truss webbing a lot of times and would end up cutting my insulation in quite a number of pieces.

    Any suggestions would be appreciated

  2. #2
    Join Date
    Mar 2008
    Location
    nova scotia, canada
    Posts
    1,522

    Default Re: Adding Insulation with trussed roof?

    blown in insulation it will fill all the nooks and crannys. its like $7.50 a bag and if you buy something like 30 bags in one shot the blower rental is free
    fire up the saw and make some dust

  3. #3
    Join Date
    Jul 2010
    Posts
    6

    Default Re: Adding Insulation with trussed roof?

    Jkirk thanks, but I already have the rolls of insulation at the ready!

  4. #4
    Join Date
    Mar 2008
    Location
    nova scotia, canada
    Posts
    1,522

    Default Re: Adding Insulation with trussed roof?

    in that case your stuck cutting the blankets
    fire up the saw and make some dust

  5. #5
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,779

    Default Re: Adding Insulation with trussed roof?

    You can roll the second layer in the same direction as the first, but offset by a half a lap. It will still take a lot of cutting, first cut the bat to length from joint to joint, then notch out the ends to fit around the joints.

    can you return the second bats/rolls for the blow in?

  6. #6
    Join Date
    Jul 2010
    Posts
    6

    Default Re: Adding Insulation with trussed roof?

    keith3267 thanks that's an interesting idea. I guess what you saying is cut each roll in half lengthwise and trim to fit up against the truss webbing.

    Too late to return the insulation now so it looks like whatever I choose it will entail a lot of cutting.

    Thanks.

  7. #7
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,779

    Default Re: Adding Insulation with trussed roof?

    No, thats not what I meant. I meant for the rolls to cover the bottom 2x4 of the truss. You would not cut them in half lengthwise.

    When you put down the first layer, you have a seam on each side of the bottom 2x4 (the joist so to speak). If you put the next layer crosswise, it will have seams going in the other direction. at the intersection of the seams, you will have little holes.

    By running the insulation over the seams lengthwise, you cover the seams below completely, except where the verticals are attached to the bottom piece. For that reason, the rolls have to be cut to the length, center to center of each of the vertical supports, then notched around them.

    One little problem with this is that the rolls on the second layer will not touch each other on the edges if they are centered over the bottom of the truss. They are reduced in width to compensate for the 2x element, so there will be a gap down the center between each truss. You can of course, center the first roll of the second layer on the center truss, then butt the adjoining rolls together until the seam gets with in about 4" of one truss, then split one roll in half lengthwise and start over with full width rolls again.

    Pack any leftover fiberglass around those vertical elements of the truss.

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