喷雾泡沫绝缘热桥接
GBA编辑器|Posted inEnergy Efficiency and Durabilityon
If you have 2×12 rafters and are installing approximately 5 inches of foam do you need to encase the rafters in foam to prevent heat loss through the top of the 1 1/2″ of rafter? Or is the heat loss so insignificant that totally encasing the rafter in foam would prove to be unnecessary?
加里
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答复
The higher the R-value of cavity insulation, the more significant become the thermal bridges. It is imperative on a well-insulated house to reduce thermal bridging.
加里,
这是另一种方法：
1.安装5英寸的闭孔喷雾泡沫。
2.在椽子下安装连续的刚性多异氰泡沫塑料泡沫。用1x3或1x4捆扎捆绑聚异构。
3.在泡沫中戳孔并安装密集的纤维素以填充椽子湾。
4.用罐装泡沫密封孔。
Thermal bridging problem solved. And your ceiling has a higher R-value.
加里,
更好地纠正热桥接的方法是安装CZ所需的全部量R值。如果R38> 5“闭孔或10”开通电池+ 1“-2”或屋顶装饰顶部的刚性绝缘。
遗憾的是，随着“性能”代码的引入，人们正在使用较少的屋顶绝缘，其中凝结是非常可能的，并且在以后可能发生许多问题。我确实在大多数家庭上指定泡沫绝缘，但必须右转，特别是在较冷的气候中完成。
所有天花板都应该在椽子下有一个聚异构层（或用于该物质的天花板），以减少热桥接？
JR,
If you want to address thermal bridging through framing members, you have three choices:
1.连续外部泡沫。
2.连续内部泡沫。
3. Redundant staggered framing, with the space between the staggered framing members filled with insulation.
Thermal bridging is very important to address. For attics, the best way is a fire rated polyisocyanate foil faced insulation with cellulose as mentioned before. The idea of insulation on the outside is not a good idea except when membrane roofing is used.
马丁，在你的＃2反应中你是否关心双蒸汽屏障？我意识到，用5英寸的闭孔泡沫，蒸汽驱动器或空气通过多元组泄漏不应该很多，但它看起来并不是一种非常宽容的隔离方式。为什么不跳过5英寸的闭合细胞？
Michael,
I agree with your recommendation. If I were writing the specs, I'd skip the spray foam.
这是加里谁提出了喷雾泡沫，我正在响应他的建议。
马丁,
Gotcha。
加里,
从您所说的案例开始，“如果您有2x12椽子，并且安装大约5英寸的泡沫”
你的问题是，“你需要加入泡沫中的椽子，以防止通过椽子的1 1/2”的顶部进行热量损失？“
我假设你的意思是椽子的底部，而不是顶部，因为泡沫通常施加到屋顶护套的下侧。
There is significant heat loss through that thermal bridge, and there is also the risk of condensation somewhere near the mid-point of the rafter depth eventually causing structural failure. The "picture-framed" system of foam installation helps reduce that risk. Encasing the entire rafter in foam is possible but not usually done because it would interfere with interior finishes.
马丁,
I'll take choice number four: create a parallel-chord truss (a reversed Riversong Truss), by dropping a 2x3 or 2x4 below each rafter gusseted 24" oc with 1/2" plywood strips on alternating sides.
这与选择＃3 - 冗余交错框架不同 - 并且使用较少的木材并提供出色的热断裂，并且可以用厚度且湿热的出现问题喷雾泡沫的充分增加的绝缘空间可以用致密包纤维素和通风通道代替更耐用的屋顶系统。（或者，用平行和弦桁架框架框架）。
Option #5 is to insulate at the ceiling level with sufficient depth of blown cellulose to bury the framing and eliminate thermal bridging. This is the least expensive option and offers almost unlimited R-value.
加里,
If you want a quantified answer: assuming your 5" of spray foam is closed cell at R-5.9/inch and your 2x12 rafters are 16" oc, you will have at least a 26% R-value degradation because of thermal bridging through the rafters, and probably more because of 3D heat loss effects. The assembly will have an effective R-value of 21.9, which is woefully insufficient in all US climate zones.
亚历克斯，
我会选择第5期
罗伯特，
我认为你的选择＃5是来自此线程的实习架构应该考虑的内容：
//m.etiketa4.com/community/forum/energy-efficiency-and-durability/16857/whats-best-thickness-polyiso-roof-insulation
Avoid Dormers and vaulted ceilings (Keep It Simple,eh)
你是加拿大人吗？
我来自北德克萨斯州北德克萨斯州
我仍然认为,人从所有气候可以learn much from Canadians, Germans, and youz guys from Vermont
我觉得你的优势是你有一个非常大的度数
As the price of Energy rises.... the rest of us will be in your boat.
You have been in the boat much longer.
We'd be glad to share some with you ;-)
马丁
基于您之前的回复（下面），似乎将泡沫放在内墙上，不必处理将其放在外观上并不得不处理窗户周围的闪光，但是......
JR,
If you want to address thermal bridging through framing members, you have three choices:
1.连续外部泡沫。
2.连续内部泡沫。
3. Redundant staggered framing, with the space between the staggered framing members filled with insulation.
JR
JR,
是否更容易将刚性泡沫放在墙壁的内侧或外部取决于许多因素：
1.它是新的建设还是改造？
2. How thick is the foam?
3. What's the siding?
不同的建筑商将对任何一种方法的挑战不同。
Here's the bottom line: Exterior foam ALWAYS performs better than interior foam, because exterior foam covers the rim joists.
马丁
New construction..1/2" polyiso..vg red cedar clapboard...2x6 walls..blown celluose insulation between the studs..
IIF在地下室中使用开放电池泡沫的一个在哪里绝缘阻挡者将是一种可接受的方法，代替外部泡沫在边缘托辋上？
JR
我们已经建造了多个房屋，方法罗伯特在第10篇文章中描述 - 选项4.它并不是难以建造和摆脱喷雾泡沫挽救了一堆钱（更不用说喷雾泡沫的温室气体）我们撕裂长2x6的一半并从左边涂抹胶囊，所有切割到相同的长度，所以你可以将它们附着在2x3的位置，然后将它们推到位，露出屋顶护套。壁板订书机适用于附件。