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Insulating under a flat roof

I have a 1929 row home, end of row, with a flat roof, which I heat with oil. Needless to say, I've been looking at ways to make my home more energy efficient without making drastic changes to it. So far, I've decided to keep the original windows - I also have storm windows - because I don't believe new windows will make enough of a difference. And I love the old wood, double hung windows. And I have 22 windows - need I say more?

I do believe adding insulation - there currently isn't any - in the crawl space between the ceiling and the roof will make a big difference. I've gotten two quotes. One wants to fill the entire crawl space with insulation because if any air space is left, he says there will be condensation leading to mold and wood rot on the roof structure. The other contractor wants to leave air space because if it is packed solid, it will cause my flat roof to "bake off".

I don't know who to believe. Has anyone had experience with this? Thank you!

Rodney H
Re: Insulating under a flat roof

Is there enough room for a contractor to get in the crawl space, to use a good closed cell spray foam between the roof rafters? I saw this done on THO one evening, some time ago, but not with just a small crawl space. Just fill the voids between the rafters with the spray foam, and you will be good to go, plus you will not need a vapor barrier.

Good luck. Hope you save lots of energy bills this winter, as well as summer. No insulation up there will make your air conditioner run way too much, as well.

Good luck.

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