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Community and Q&A

Cold access room – Air barrier gaps between roofline and exterior wall

JDuchek24 | Posted in General Questions on

Hi Everyone,

I recently bought a house outside of Chicago (climate zone 5) which has been added on to several times (including “popping the top”). On the second story, there is a crawlspace / dryer vent access “room” which is on the front side of the house. The front wall to this room (approximately 12 – 15 feet long) is an exterior wall of our wood frame / metal sided house. The roof slopes down through this room and extends onward to our front porch. The room is unfinished (studs all around the interior) and is only accessible via a scuttle door from a bedroom, but is part of the thermal envelope, with conditioned space on the three other sides of this room.

With the cold temperatures in Chicago, I noticed that the room was far colder than it should be (even for having no direct heating source). After feeling around the slightly torn kraft faced fiberglass batts (approx. R-19) which fill the cavities between the roof studs and the exterior wall studs, I realized that cold air was blowing into the room around where the roof line intersected the exterior wall. Pulling back one of the batts revealed a 10” high gap between the roof line and the exterior wall (through which I can look down into the interior of the porch ceiling area). These 10” gaps are present between each of the 16in o.c. exterior facing studs in this room and presumably also on most of the rest of the front of the house since the porch spans nearly the entire front of the house. The kraft faced batts have (sort of) plugged the gap and hidden the issue until now. The floor of the bedroom near this room (also on the front side of the house) is also cold.

Questions / comments:
– Is there any legitimate reason for having these gaps in the air barrier? I assume no, but wanted to check before I plug all of them

– I have started to plug the gaps with 1in polyiso and caulk, which seems to help. My thoughts are to plug the rest of the gaps with the polyiso, add a bit more unfaced insulation in the cavity (as properly as I can) and then tack another inch of polyiso onto the interior side of the studs and air seal accordingly (I would add furring strips and drywall if needed). Thoughts on this approach? Any concern with having two layers of polyiso separated by a couple inches of fiberglass (e.g. moisture in the cavity around the wall studs and roofline studs)? I don’t have any observable moisture problems currently in the house.

– Any other ideas why the nearby bedroom floor would be colder than other parts of the floor on the same story?

Given that we don’t actively use the access room, I am fine for it to be a bit colder, but want to stem the energy loss and hopefully bring some improvement to the nearby bedroom (as I’m pretty sure the air barrier gap / cold air is impacting the wood under that room). I guess longer term I need to get into the porch roof area and assess all of the air barrier gaps across the front of the house, but that’s a summer project. (I also have a cold kneewall over the garage and ducts in the attic, but those are posts for another day…)

I appreciate any feedback provided. Thanks in advance.


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  1. GBA Editor
    Martin Holladay | | #1

    You accidentally posted your question twice. Your question has already been answered on the other page. Here is a link to the page with the answer: Joe Duchek's post with answer.

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