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Wrapping up the Cape cod attic insulation.

davemax21 | Posted in General Questions on

Martin,
I wanted to thank you for all your time spent responding to my insulation questions. I have read all the literature provided to better equip myself in knowing more about my home.
One final piece of advice from you if I may.
I do have a reputable GC/home builder, who has done very nice work at my home, “you get what you pay for here”.. he has over 30 years in the business, has lots of “letters” after his name, lol. And even has a radio show on the weekends, for what it’s worth. So, basically, I trust his expertise, he speaks of the bld. envelope quite a bit, etc..

Wanted to know if you would concur; regarding the one and half story cape style home I have. In insulating the attic and sloped ceilings, knee walls, been told that instead of putting in soffit vents, baffles, or even foam board under roof shingles, etc.., that I will have , or he will have, the luxury of having all ceilings and knee walls gutted. All insulation removed first, the gutted.
All air leaks sealed in attic floor, and others, then , because the rafters are not very deep, old home, and because cost is not too much of an issue, that he would spray foam knee walls, sloped part of ceilings to where they meet the flat attic floor, then drywall up, then blown in cellulose in attic.
Said this would be preferred , namely because of having good access being that it will be exposed/gutted.
Any final thoughts?
Dave

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Dave,
    It's fine to pursue a gut rehab job that involves all new insulation. My only comment is that it makes more sense to install the insulation along the roofline in the area behind the kneewall, and to leave the kneewall uninsulated. Otherwise, you have to get involved with tricky air sealing details in the joist spaces under the kneewall bottom plate, and in the rafter spaces above the kneewall top plate.

    For more information on why I don't think you should insulaye the kneewall, see this article: “Two Ways to Insulate Attic Kneewalls.”

    -- Martin Holladay

  2. GBA Editor
    Martin Holladay | | #2

    Dave,
    If you don't have any attics behind the kneewalls, then your plan is fine.

    -- Martin Holladay

  3. davemax21 | | #3

    Thank you. Again I was not clear/confused as to what I call the knee wall.
    I don't think my home has knee walls. As I showed in the picture previously, mine is more of the raised cape .
    My ceiling doesn't slope all the way down to what would be the bedroom floors, where they would have the small knee wall of course in front of it.
    My ceilings slope to about 3 feet up the sides up the house. On one side of the bedroom, there is no closet, just where the roof line slopes , then hits the exterior wall about 3 feet up. The other sides there is actually a closet you can walk in, standard doorway height, then you can see the continuance of the slope above to again, about 3 feet up from the exterior walls. Unless the outer closet wall that goes up to the sloped ceiling is considered a 6' tall knee wall? So looking at new diagrams of knee walls, I would have a 6 foot knee wall, that supports the sloped ceiling that bottoms out at 3 feet up from the "closet floor". And these are closets we use.
    So , the "shorter" exterior wall is what I was referring to as the knee wall.
    So I guess , that will be gutted, and the ceilings, and the spray foam would just be on the shorter exterior wall, and then up the slope.
    Does that make more sense to you Martin, and does that sound like a plan. This way nothing would be dense packed in , etc...

  4. davemax21 | | #4

    hoping this pic comes thru

  5. davemax21 | | #5

    the pic is very similar to mine. the back of that closet wall is the exterior of the house, nothing more behind it.
    That's why we thought with the drywall removed to just spray foam that exterior wall and the sloped ceiling, then blow in to cover the attic deck floor.

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