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adding attic insulation with hip roof

Post in 'DIY and General non-hearth advice' started by bsa0021, Jan 29, 2012.

  1. bsa0021

    bsa0021 Feeling the Heat

    Joined:
    Oct 1, 2008
    Messages:
    405
    Loc:
    Ohio
    I have a 1950s ranch with a hip roof that I am adding roll insulation over the blown insulation. The rolls are running across the joists. With the hip roof design the roof joists run close to the floor joists for about 30" to the eves. I know I have to keep an air space up from the eves but how far back do I put the rolls? I put a roll back until it started to touch the roof joists with plenty of air space but its still about 30" away from the wall below. If I install baffles, I could push the insulation back further but the r30 insulation would be crushed against the roof joists.

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  2. FGZ

    FGZ Member

    Joined:
    Nov 19, 2010
    Messages:
    78
    Loc:
    N.Shore MA
    I have a similar design, interested to hear opinions. Bump for ya!
  3. Lumber-Jack

    Lumber-Jack Minister of Fire

    Joined:
    Dec 29, 2008
    Messages:
    1,735
    Loc:
    Beautiful British Columbia
    In a lot of modern blown-in insulation jobs I have seen, the guys install the air vent "baffles" and then stuff a piece of rigid batt insulation between the baffle and the top wall plate to plug the holes before blowing the insulation in. The rigid piece of insulation acts as a plug to stop the loose blown in insulation from leaking out, and it also stops strong winds from blowing in past the baffle and causing the loose blown in insulation from drifting inside the attic. I have seen areas inside attics where the wind managed to get in under the eaves and blow the loose insulation around causing it to form sort of snow drifts, so there ended up being piles of insulation in some areas and bare areas where there was no insulation.
    So, a little compressed insulatin around the baffles is a good thing.
  4. DAKSY

    DAKSY Patriot Guard Rider Staff Member

    Joined:
    Dec 2, 2008
    Messages:
    4,893
    Loc:
    Averill Park, NY, on Burden Lake II...
    Use the Prop-R-Vents, or whatever brand of styrofoam is
    sold in your area, to keep the air passage open &"notch"
    the batts where they will meet the rafters so that the entire
    surface doesn't get compressed. You want to get those batts
    over the top of your walls & tight against the styofoam...
    As an aside to that, make sure you wear a Hardhat when you
    do the job. Roofing nails leave nasty scars on your noggin.
    Don't ask me how I found THAT out... :-S
  5. bsa0021

    bsa0021 Feeling the Heat

    Joined:
    Oct 1, 2008
    Messages:
    405
    Loc:
    Ohio
    Thanks for the info Dasky. I wasn't sure if I would have to cut a small piece for each joist. Your way will be more airtight.
  6. gitmo234

    gitmo234 Member

    Joined:
    Dec 1, 2010
    Messages:
    80
    Loc:
    Oxford, PA
    Youre going to feel a HUGE difference. I laid down R30 over my blown in (ranged from R12 depth to R20) insulation. I have four heat registers in the bedroom and with the new insulation I closed two (four is ridiculous anyways) because it was WAY too hot and my thermostat was in there. The other rooms are too open for the thermostat, so with those two shut and the insulation Ive managed to balance the heat in the whole house to registering roughly the same..within two degrees max

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