刚性与喷雾泡沫为屋顶
I am finalizing the construction spec on our planned home in Houston (intended to be a ‘pretty good house’) and although this has been talked about here in many forms it’s rarely linked to actual cost numbers.
I originally looked at using 2″ recycled rigid foam above the roof and blown-in insulation below it to achieve the required code values and create an enclosed attic with an unvented roof (as per GBA Cathedral Ceiling Article). The tales of spray foam gone wrong were a strong push in this direction.
However after costing, my contractor has come back and said that there’s a lot of extra work and material in the rigid foam solution (with sheathing both above and below it) and that a closed cell spray foam approach would be approx. $1000 less overall and significantly simpler for him in terms of execution as well as air sealing benefits etc.
The spray foam contractor would be a well established one with a long track record of doing custom and production homes in the Houston area who our contractor has worked with before.
If it were your house and your money, what approach would you take to give you peace of mind in terms of long term performance and reliability (a LOT of roofs in Houston leaked during Harvey…).
Thanks!
GBA详细资料库
由气候和房屋部件组织的一千个建筑细节的集合
答复
用户-68ETC。，
First of all, can you tell us your name?
当你建造一所房子时，1,000美元的上涨并不多 - 但我明白一些预算很紧张。
Clearly, the option with exterior rigid foam is more effective at addressing thermal bridging through the rafters.
知道两个选项的R值是否相同，这将是有趣的。（换句话说，这是一个苹果到苹果比较，或者一个选项具有更高的r-value？）
It would also be interesting to know if your contractor will use closed-cell spray foam or open-cell spray foam. (I would never use open-cell spray foam on the underside of roof sheathing unless the roof assembly also had rigid foam above the roof sheathing. If the insulation is all being installed on the interior, use closed-cell spray foam.)
有关更多信息，请参阅这两个文章：
High Humidity in Unvented Conditioned Attics
Open-Cell Spray Foam and Damp Roof Sheathing
I'm a homeowner not a contractor but I'm perplexed at some of your numbers. What is your roof R requirement? Around here recycled polyiso is $16/sheet for 2" thickness . Closed cell spray foam for that same R value would cost twice the price per square ft. Unless cost was substantial (IMHO $1,000 is not) I would stick with the polyiso and even try to do all of the roof in polyiso. I'd imagine the extra polyiso material and screw length would not cost more than the blown in material (assuming you don't need more than 4" above the deck). Also the total R requirement is slightly lower if all of the insulation is above the deck.
正如上面提到的马丁一样，聚四多屋顶会更好。也许你的承包商应该联系商业屋顶。坡度屋顶经验低的人应该多次处理您的情况。或者你可以为屋顶购买钉子板，看看他是否减少了他的劳动力。
Good luck!
Brandon
Ok, profile should now be fixed to show my name. So Martin, spray foam would be closed cell, based off previous articles here.
假定为目的的这种比较v Ralue is roughly equivalent (unlikely to differ by more than 5). So your really comparing air sealing vs thermal bridging qualities and practical issues like observing and repairing leaks in the long term.
布兰登 - 关于成本，差异是泡沫顶部所需的额外OSB层和安装它的额外劳动力。这是一个有趣的想法，只能在顶部僵硬，但我认为我们将在6英寸以获得最低限度的R-30。这也是一个公平的额外劳动力，做3层泡沫和劳动力在休斯顿的优质在Harvey之后。我可以询问这个选项是如何比较的，因为它删除了吹吹绝缘体。但是我提醒了来自另一个GBA文章的报价：
“当Alex Cheimets在马萨诸塞州阿灵顿的房子的深度电气改造时，他指定了6英寸的刚性泡沫，应安装在屋顶护套上方。由于GBA报道，“一盒破碎的10英寸螺丝，一套新的冲击驱动因素，以及一周的挫败感以后，[承包商]想知道它是否值得。到底，屋顶齐全，但[一些团队成员认为，额外的努力和成本很难证明。“
您可能仅在屋顶上的外部绝缘层看到的任何其他问题？这个屋顶上也会有太阳能电池板。
我明白了大约1000美元，但现实是在房屋项目上有十几个决定，并且在房子上只有一点点变成了10,000美元的影响，所以我必须严格了解每个设计决定。然而，与化学污染相比，它也很便宜......
Thanks!
也许不是 - 它是马克斯。
马克，
您要检查的另一件事是您的喷雾泡沫安装器是否包括喷雾泡沫的内侧上的热屏障或点火屏障。在一些司法管辖区，地方代码当局不执行热障碍和点火障碍的要求 - 但房主应记住暴露的喷雾泡沫是火灾危险。
有关更多信息，请参阅本文：Thermal Barriers and Ignition Barriers for Spray Foam。
谢谢马丁 - 看着你的文章看起来像泡沫下的吹绝缘会符合点火屏障的作用。这将是所提出的方法（3-4英寸的封闭电池，另外4英寸的绝缘材料或贝尔）
Markus