边缘托梁绝缘: No wood sill plate – influence on rigid foam
晚上好，
I have been reading posts on this forum for the last year and greatly appreciate the thoughts offered. I own a 75 year old stone/brick colonial in SE Pennsylvania (region 4a). The basement is unfinished and the sill boxes are not insulated. I would like to utilize rigid foam (foil faced PolyIso) with spray foam to insulate the sill boxes.
However, the joists sit directly on top of the concrete wall, there does not seem to be a wood sill plate (see attached photo illustrating a representative sill box, note the joist (right) sits on the concrete wall). The diagrams for insulating rim joists indicate that the rigid foam should sit on the wood sill plate, which I presume limits a direct water uptake path from concrete to foam insulation.
Given the lack of a sill plate to rest the insulation on top of, what do I need to be aware of? Can I continue to utilize rigid foam directly on top of the concrete, do I need to place a ‘capillary barrier’ under the insulation and if so what would be the most appropriate material?
Thank you in advance,
Scott Fillery
GBA Detail Library
由气候和房屋部分组织的一千个建筑细节的集合
Replies
I don't recognize all of what I'm looking at. Probably someone else who does would give a better answer, but in hopes of jump-starting the process, I'll ask about what I don't understand. First, the joist on the left looks dark for the bottom 40% and light for the top 60%. What's going on there? Second, it looks like there is a white layer of something on top of of the foundation, under the mortar. Is that a plastic layer?
Hi Charlie,
I will hopefully offer a better explanation the second time. The picture in the above post and an improved picture below are of one sill box. The previous picture included a sister joist which I don't believe is critical to the question - so I have taken another picture of a neighboring sill box. The far wall is brick that sits directly on top of the concrete basement wall (no sill plate). The floor joists sit on / are embedded into the top of the concrete basement wall. The concrete ( block maybe) wall looks to have parged and sealed with 'dry-lock', hence the white look. At the back of the box, the bottom of the brick masonry has mortar buildup due to the joist embedding.
I would like to insulate these sill boxes to limit air leakage. My questions are as follows:
1.没有门槛板，在裸露的混凝土脸上静止的刚性泡沫会带来问题。
2.我不能直接休息固定的泡沫，接下来是窗台背面的砖头 - 砂浆可防止这一点。因此，我会向前移动刚性泡沫，从而在砖头和泡沫之间留出一个空间。但是，这可能会达到两个不良物质：（a）我可能有一个可以捕获冷凝的空气口袋（??）。（b）一部分地板托梁将在刚性泡沫层后面，从混凝土或空气泄漏到气口中的任何冷凝物旋转。
What options are best? (i) do nothing and accept the air leakage. (ii) utilize the rigid foam technique but not at the brick face. (iii) utilize spray foam onto the brick face, but realize that there could be a change in moisture in the brick leading to more rapid brick deterioration.
Note the iPhone rotates the picture 90degrees for some unknown reason. The left side is the concrete basement wall, the right side is the subfloor.
Scott - How many inches deep is the space, from concrete foundation to brick? Is the foundation below the joists above grade? Since the space looks so rough you have a big challenge. There are also wires running through there that may need access to in the future. If this were mine and I was committed to insulating it, I would fill the space with mineral wool, then place 3/4" wood strips on the floor joists and subfloor in plane with the concrete foundation. I would then fix water resistant drywall to the wood strips and foundation using construction adhesive or polyurethane caulk, and screws into the wood. After attaching, re-caulk the edges of the drywall.The drywall would allow some degree of drying potential to the inside from any possible condensation on the brick,while preventing warm air into the space. I'm concerned that the foundation wall, especially above grade needs to be insulated as well, probably just as badly, and this might change the approach. Some people would spray- foam this space, and be done, but it's quite unforgiving if repairs/maintenance are required down the road. Others more experienced with this situation will hopefully chime in. Good luck!
Kevin,
谢谢您的建议。
The answer to you're questions are as follows:
1.窗帘盒深度-10英寸（从地下室墙的砖面到边缘）。
2.混凝土基础墙的顶部约为当前等级8-10英寸。因此，窗台盒的顶部位于坡度。
As you mentioned I am very interested in hearing everyone's opinions. I am interested in the right way (after accounting for pros/cons) regardless of effort.
斯科特（Scott） - 由于我们现在知道地板托梁低于级别，因此我的上述建议必须被撤回，因为零可能会使外部干燥，并且这些内部地板托梁将更容易受到水分积累的影响。我不确定如果没有将结构置于风险的情况下，您是否可以安全地完成任何操作。您的努力可能会更好地花在其他地方，绝缘和空气密封高于等级。我很难想象一个适合您的情况的系统，可以使这种结构持续75年。我希望其他人会为您提供一些更好的建议。
Scott - Read Martin's blog at this site, "Insulating Old Brick Buildings". While talking about above grade walls, the concepts covered have similar bearing to your situation.
Scott,
这是凯文（Kevin）谈论的文章的链接：绝缘旧砖建筑.
I have to agree with Kevin that your situation is difficult to resolve. There are several problems here:
1. It's never a good idea for a foundation to be backfilled above the top of the foundation wall.
2. It's never a good idea for floor joists to be below grade.
3. It's never a good idea to embed floor joists in masonry.
4. Insulating this area will definitely make the bricks colder (and therefore wetter). This could cause the ends of your joists to rot.
没有简单的修复。我可以想象一个修复程序 - 但这并不便宜。它可能涉及将您的等级降低到基础墙顶部的8英寸 - 这可能是不可能的。充其量，它可能会引起美学问题，并需要您的门廊或条目的新步骤。最糟糕的是，您的美化环境可能使这种方法变得不可能。
我还可以想象“电锯解决方案”：切断嵌入式托梁的末端，并用新的轴承墙支撑切割末端。也不便宜。
The easiest solutions are either (a) Do nothing, and keep an eye on everything, or (b) Sell the house.
How about exterior insulation for that region, perhaps mineral wool boards? Dig down 1.5 feet by hand to install?
Charlie,
Your suggestion is a good one. That approach would solve some, but not all, of this home's problems.
Of course, the above-grade portion of exterior mineral wool would need to be protected from physical abuse on the exterior with some type of material like metal flashing or pressure-treated plywood, and the insulation would also need horizontal Z-flashing at the top of the insulation -- flashed into a horizontal mortar joint in the exterior brick.
查理——除了,而背后的exterior mineral wool the bricks would stay warmer, the bricks above the insulation would stay cold and conduct the heat from the warm bricks, a super thermal break that seems like it would negate a lot of the benefit.
马丁，Kevin and Charlie
Thank you for help. I was aware of this potential after I cleaned away the debri. The cost benefit does not outweigh the potential impact. Regarding re-grading, I have the ability to regrade half of the sill boxes, down to a couple inches below the foundation wall, but not 8". Is 8" a hard number?
另一个问题是，与托梁结构平行的基础墙在墙壁顶部带有一个小窗帘板。这些区域保持在坡度以下大约3英寸。我可以填补木材的接缝吗？我读到这些区域不是高空泄漏区域，所以我再次想知道成本收益。
非常感谢，斯科特
Scott,
如果您可以降低外部等级，以使坡度在基础墙的顶部下方2英寸处，那对当前情况是一个很大的改进。如果这是我的房子，我会那样做。
I would also make sure that the roof has functioning gutters, and that conductor pipes convey the roof water to a location far from the house.
填补任何明显的空气泄漏总是一个好主意。填缝空气泄漏不会引起任何水分问题。
马丁，
得益于一些合理的天气,大多数(2/3)的e foundation below grade has been re- graded so that the soil is 2-3 in. below the top of the foundation wall (current grade features a min. 6" drop over 10ft). I will wait and observe the sill boxes, but I would like to seal at a later date. Given this change in grade, as well as gutter extensions I fixed last year, can I take up Kevin's suggestion?
Many thanks for you're advice, I feel better having acted on the grading issue before a major landscape planting.
Scott
Scott,
Q. "Can I take up Kevin's suggestion?"
A. You didn't specify which of Kevin's suggestions you're thinking about, but I'm guessing that you are talking about the idea of insulating the rim joist on the interior with mineral wool.
To me, that's a risky approach (because air-permeable insulation allows humid indoor air to contact the cold rim joist.) Carefully installing airtight rectangles of drywall on the interior side of the mineral wool may help, but it's not a foolproof solution.
Only you can decide whether to try that approach. The level of risk depends in part on how humid your basement is. The colder the climate, the riskier it is to use mineral wool in this location -- and this fact argues in your favor, because Climate Zone 4 is relatively warm.