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heat loss

the interstitial (void) space is as well insulated around the perimeter as it is above and below, but does not have heat added to it specifically, I would calculate it as about half-way between your indoor and outdoor temperatures. Say your design is 0 outside and 70 inside, I would calculate it as being 35F.

In actual practice it may well be a higher temperature but the old roof insulation blocks the first source of heat (the floor below).

My initial point remains though, insulate the perimeter and if at all possible, use a spray foam such as Tiger Foam for air sealing. Insulation aside, a good air leak will ruin your day.


  • joseph annon
    joseph annon Member Posts: 53
    heat loss on second floor addition

    I have a question about heat loss on second floor addition on a "flat roof" home.
    The home has an existing insulated roof with an addition over the entire roof. There will be a space between the first and second floors that starts at about 12" high to 30" high this is due to the slope of the original roof.
    Is the second floor considered to be over non heated crawl space or over heated space. I can think of reasons for both designations. There will be air vents for air circulation and there will be an access panel.
    Have not run across this before and would like others opinions.
    The addition will have a gypecrete overpour with radiant tubing in the gypecrete.

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