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Thread: Re-roofing houses with added insulation

  1. #1
    I'd rather C2E than work!
    Join Date
    Mar 2006
    Edmonton (Norwood)

    Default Re-roofing houses with added insulation

    Many early and mid-20th century houses were built with upper partial stories where a steeply pitched roof became a sloped ceiling on the inside. While this makes for attractive architecture and interesting character, the construction techniques of the day did not leave enough room for insulation as the roof deck was attached to one side of the 2x6 (or sometimes even 2x4) rafters, and the ceiling to the other. Adding insulation to the inside sacrifices already scarce headroom, which makes adding insulation to the outside when re-roofing an attractive possibility. Anyone have any experience with this?

  2. #2


    Two neighbours have done so one 1-1/2 story houses, one as part of a substantial Reno, the other just roof and siding. It looked like a fairly simple process, though.
    No idea on costs though.
    There can only be one.

  3. #3


    I take it you are referring to cathedral ceilings. At one time we owned a home with a cathedral ceiling and I did not find the heat loss to be to great but then again it was a new build. To me it would seem like a big job to blow insulation into each joist space as how could you go about this without either putting holes in the ceiling or removing it altogether. Same as spraying that foam insulation in that hardens. Even if a person needed a new roof how could insulation be applied without taking off the outer layer of the roof. I don't know if there is any type of insulation that can be added on the outside of the roof (under roof tiles) as what could be used that would be 100% weatherproof.
    Gone............................and very quickly forgotten may I add.

  4. #4


    Regarding "A frame" style attics. In Edmonton I would guess 2x4 construction would be the norm from my experience ( (at least 95% likely). The problem with strapping the entire roof with Sm board is the breath ability is still compromised . By code there needs to be cross ventilation from rafter cavities.

    I I did a renovation 2 years ago where I strapped the rafters 2" on the original 2x4 from the inside. Had the entire roof sprayed with closed cell insulation ( no air space needed as it works as a vapour barrier and does not need to breath) the cost was $1 per square foot per inch deep. The company I used was foam force, they did a great job! In one day the attic was sprayed and cleaned up, the next day we were hanging drywall.

    in an a frame application I would spray from below the pony walls to the ridge board. Maintain vapour barrier on walls and keep loose fill or batt in lower sections. I was able to get r6.47 per inch. with the product that was used on my application
    Last edited by Swillv8; 02-03-2017 at 07:32 PM.


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