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  1. #1
    Join Date
    Apr 2014
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    2

    Default Q's about insulation settling and insulating over a porch

    Trying to make use of some fiberglass insulation that is on hand and have some questions.

    1) How much settling in old loose insulation is acceptable and can you simply lay fiberglass insulation over the loose insulation? The old insulation is settled roughly an inch below the rafters - if I lay in the fiberglass it would set 2-3 inches above the rafters with a rafter-width gap between each one. Doesn't seem like that would do much good.

    2) After laying fiberglass insulation into some empty bays I realized those bays are over the porch. What's the effect, if any, of insulating over the porch. Does the insulation need to be removed or is it just wasted effort, but no harm done?

    Thanks.

  2. #2
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,940

    Default Re: Q's about insulation settling and insulating over a porch

    If you are talking about old style loose insulation that has packed itself down, I'd lay the batt insulation across the top of the joists, perpendicular to them with the batts sug against each other.

  3. #3
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    6,376

    Default Re: Q's about insulation settling and insulating over a porch

    The only trouble with Houston's suggestion is: what if you go in your attic a lot - how will you find the joists once they are hidden under a ton of insulation?

    If the old loose insulation in compacted, you can set the batts in between the joists and still see the joist when you are in the attic.

  4. #4
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,940

    Default Re: Q's about insulation settling and insulating over a porch

    how will you find the joists once they are hidden under a ton of insulation?
    Simple; When you step between them and fall through to the room below, the joist will be right under your......

  5. #5
    Join Date
    Jan 2008
    Posts
    1,977

    Default Re: Q's about insulation settling and insulating over a porch

    Or do enough framing- after walking on joists long enough you can pace exactly 16" and 32" exactly without even looking!

    Back on topic, the R-value of insulation is related to it's thickness (depth in this case) so if it's settled, it has lost some effectiveness. You can "fluff" it back up but it will eventually settle again. Just lay the fiberglass batts over it in the joist bays and don't worry about it, the added insulation will be quite a lot better than what you've got now.

    Phil

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