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Community and Q&A

Insulation over roof shingles?

brow1938 | Posted in General Questions on

I recently moved my family into a home where the original 1924 two-story house was added onto, as near as we can tell, somewhere in the 1980’s. The addition consists of a large living room, bedroom, and bathroom over a tuck under 2 car garage. In looking in the attic of the newer portion, I can see the shingles of a portion of the roof on the original, older part of the home to which the addition was framed directly on to. From outside looking at the rooflines where the old and new meet, there is a valley. From the inside, the portion of the roof I can see from the attic is the angled ceiling and knee wall of my son’s upstairs bedroom. I’m getting ice dams in this valley and I suspect it’s from heat loss through the slanted ceiling of my son’s room. I’m thinking the easiest thing to do to alleviate this is by placing fiberglass batts over the shingles I can see in the attic. What would be the advantages or disadvantages of this? Any ideas or suggestions would be much appreciated. Thank you.

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  1. maine_tyler | | #1

    I'm having a hard time visualizing all this, but as a general statement, I'll say that you should consider looking for air-leaks before adding insulation, as air-leakage can be a larger contributor to heat loss and subsequent Ice-dams.
    You may consider hiring someone with equipment to detect those leaks, or you could try a DIY fan in a window and smoke stick type of deal.

  2. GBA Editor
    Brian Pontolilo | | #2

    Hi brow1938.

    You are right that ice dams are usually the result of heat loss or air leaks. It sounds like you are asking about insulating the newer addition roof, which I assume has a full layer of sheathing. Regardless, simply adding fiberglass batts to the underside of the roof is not a good idea. Insulting a roof line is tricky and the details are important to get right. I suggest you start tart with this article: How to Build an Insulated Cathedral Ceiling.

  3. brow1938 | | #3

    Thank you gentlemen for the responses. As I was typing my question I was afraid it was too lengthy and that one could be easily confused by it. I will get up into the attic to take some pictures that should clarify my original question.

  4. brow1938 | | #4

    Finally, I got up into the attic of the addition to take some pictures. What you’re looking at is the roof of the original, older part of the home. You’ll see that the roof for the addition was framed directly onto the shingles of the original roof. I’m not sure if this is standard practice, but nonetheless the shingles are still exposed. Directly underneath the shingles is my son’s room and I can’t imagine there being much insulation, if any, in the 2x4 cavity. Back to my original question, would it be advisable to place insulation over the shingles or would I be causing problems in any regard? Again, any further help would be much appreciated.

  5. 730d | | #5

    I don't see any ventilation in the pictures ?
    Never hurts to ask.

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