Cold Access Room – Gaps in Air Barrier
Re-posting to the proper Q&A category
你好 -
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 feet long) is an exterior wall of our wood frame / metal sided house. The roof slopes down through this room and continuously 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.
随着芝加哥的寒冷温度，我注意到房间远远低于它（即使没有直接加热源）。在围绕略带撕裂的牛皮纸面对玻璃纤维壁（r-19），它填充了顶板和外墙螺柱之间的空腔，我意识到冷空气吹入房间，在屋顶线相交的外墙上。拉回其中一个击球件揭示了屋顶线和外墙之间的10“高间隙（我可以俯视廊道天花板区域的内部）。在16IN O.C中的每一个之间存在这10“间隙。外墙面向这个房间的铆钉，据推测，由于门廊几乎整个前面，所以房子前面的其余部分也是如此。牛皮纸面对的蝙蝠有（有种）插上差距并隐藏在现在的问题。卧室靠近这个房间（也在房子的前侧）也很冷 - 我怀疑，因为下面的托梁不是绝缘。
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 further 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.
– The access room just has plywood in some areas. If I can open up the floor and then see what I suspect (i.e. not much insulation around the rim joists), should I try to get polyiso down there too?
– 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 reduce 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 appreciate any feedback provided. Thanks in advance. This is a great site.
Joe
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Replies
Joe,
Q. "Is there any legitimate reason for having these gaps in the air barrier?"
A. No.
问：“我已经开始用1英寸的Polyiso和Caulk插上差距，似乎有所帮助。我的想法是用Polyiso堵塞剩下的差距，在腔内添加一点更透露的绝缘（如我正确的罐头）然后将另一英寸的多自在螺柱的内侧钉在螺柱的内侧，相应地进一步空气密封（如果需要，我会添加粗束带和干墙）。对这种方法的想法？“
A. Your approach is fine.
Q.“任何两层多球分开的任何担心都会被几英寸的玻璃纤维分开（例如，墙壁上的腔体中的水分和屋顶螺柱）？”
A. No.
Q. "The access room just has plywood in some areas. If I can open up the floor and then see what I suspect (i.e. not much insulation around the rim joists), should I try to get polyiso down there too?"
A.您所有的家用的热封（地板，墙壁和天花板或屋顶）需要一个很好的空气障碍 - 这意味着没有孔，间隙或泄漏 - 以及与空气直接接触的相邻绝缘层屏障。
Q. "Any other ideas why the nearby bedroom floor would be colder than other parts of the floor on the same story?"
A. This sounds like a classic example of air leakage. The solution is simple: Plug the air leaks. Once the air sealing work is done, improve the R-value of your thermal envelope.
Thanks Martin. I appreciate the feedback.
Martin, All,
I am nearing completion of my access room insulation project (described above), but self-doubt and continuous reading of GBA Q&A (including the many vaulted ceiling questions) have caused me to fear that I may have unwittingly made a rookie mistake by creating an unvented vaulted ceiling which may experience future problems. Specifically, I tacked 1 inch foil-faced polyiso on the interior vertical wall of the room and then also tacked 1 inch of continuous polyiso directly onto the sloped ceiling studs (which are 2x10 roof rafters with unfaced fiberglass within the cavities). I air-sealed the continuous polyiso on the underside of the roof rafters with a combination of spray foam, caulk and Nashua foil-faced tape at each seam and everywhere the polyiso meets wood. I now realize that polyiso and fiberglass batts are not listed under the unvented ceiling options...
See attached photo better illustration.
Facts:
- Climate Zone 5A (near Chicago)
- Sloped Ceiling stack-up from inside to out: 1in continuous polyiso, 9.5in of low density fiberglass batts between 2x10s, plywood and standard shingles on the roof. I doubt we have any "fancy" stuff / Ice & Water shield on the exterior side of the roof given other construction techniques used when the second story was added on, but I cannot (yet) be sure. I can find out.
- This room (and the sloped ceiling) faces the west and represents the "mid-section" of our roof (between porch roof and uppermost attic roof) and does not span the entire length of the roof.
- Adding baffles / venting channel would be possible in certain places, but may be somewhat ineffective because I don't have a completely clear path to the main attic / ridge vent in all cases.
- No direct HVAC in the room
- Room held temperature reasonably well once polyiso was up. (We still had cold temps in March)
- We don't heat above 66 degrees in the winter and therefore this room (even with the polyiso) will likely never be above 60 degrees in the coldest days of winter. (We also don't blast AC in the couple weeks that it is needed)
- A dryer exhaust ducting goes through this room, adding some heat occasionally. The ducting is air sealed where it means the polyiso. There are also PVC and black iron penetrations which are air sealed
- No apparent moisture issues before during or after the project
- I don't want to use spray foam
Questions
- How risky do you judge this setup (i.e. how bad did I screw up)?
- If risky, does wintertime condensation present the biggest risk?
- Can I mitigate / monitor the risk (without removing the continuous polyiso)?
I appreciate your thoughts.
问候，
Joe
Joe,
You screwed up.
这种情况有多糟糕？这很难评估。通常，由于空气泄漏，用玻璃纤维贝蒂（如您的）绝缘的未经辩护的大教堂天花板。室内空气（冬季潮湿）通过天花板裂缝进入椽子湾，导致屋顶护套的冷凝。
By creating a tight ceiling, you have lowered the risk. That's good. However, we can't assess whether you missed some cracks. For example, interior air can enter rafter bays by devious paths -- for example, through partition walls that rise up to the sloped ceiling. If your roof assembly has some of these hidden air leaks, and if you have cracks near the ridge of your roof -- most roofs do -- your roof assembly is at risk.
-- Martin Holladay
Thanks Martin. I appreciate the feedback.
Would your assessment change if there was a 1.5in venting channel (made of 1/2in EPS or XPS) moving cold air (in winter) from my porch roof cavity to the main attic (which is vented)?
Absent the venting channel option (and nixing the foam option), I guess my only other choice is to remove the polyiso and put up drywall (creating an air barrier that can dry to the interior)? Any other solutions come to mind?
问候，
Joe
Joe,
Q. "Would your assessment change if there was a 1.5 inch venting channel (made of 1/2 inch EPS or XPS) moving cold air (in winter) from my porch roof cavity to the main attic (which is vented)?"
A.添加通风通道肯定会降低您对“不需要担心”的水平的风险 - 只要通风通道位于玻璃纤维绝缘的顶部和屋顶护套的下侧之间。
-- Martin Holladay