条件阁楼“通风”
I’m building a house in Climate Zone 2A (Hot/Humid) and it will have open cell spray foam on the walls and roof deck. In order to control the humidity levels in the attic, it is suggested that a supply duct from the HVAC be installed in the attic. Alternatively, air can be supplied to the attic by a fan blowing air from the occupiable space into the attic. The physical installation of the fan blowing air into the attic seems straightforward, but my question is about the location the air intake in the “occupiable” space and the location of the exhaust into the attic. Where would the best place to pull air from (closet, living room, etc.)? Does it matter where the air is exhausted into the attic (near the highest point on the roof, opposite side of the house from the HVAC return, etc.).
答复
E247，
First of all, can you tell us your name? (I'm Martin.)
未经辩护的条件仪器中的高湿度的问题复杂化。关于如何处理这种湿度问题的许多问题没有简单的答案。一般而言，我建议建筑商和房主避免使用这种类型的阁楼闭孔喷雾泡沫使用开放式电池喷雾泡沫更安全。
For a thorough discussion of the issue, see"High Humidity in Unvented Conditioned Attics."
我读过那篇文章（以及许多人）和我的问题更多关于向阁楼向阁楼提供空气。是否有首选的地方可以从HVAC系统中汲取空气并供应空气，或者是来自HVAC系统的供应寄存器最佳选择？
我的HVAC安装程序在系统运行时安装提供约40 CFM的电源。（但我的阁楼相当小。您的设计师推荐了什么。）他还想从第三层生活空间安装回归到阁楼。但我延迟了这一步，直到我在阁楼里的条件下有更多数据。
To collect that data, I installed a SensorPush sensor near the attic peak. Long-term I may install a vapor diffusion port or mechanical dehumidification if humidity levels in the attic become worrisome.
The HVAC design called for a 50 cfm supply vent in the attic, but it was missed during the installation of the ducts. I can have them come back and install the supply vent, but I think it would be easier to use a fan to supply air from the house to the attic. My main question was where is the best place to draw the air from and if it makes sense to exhaust this air near the peak of the roof since that's where the humid air tends to collect.
It is my understanding that what you are doing is returning air to the attic. A builder I know always puts in a return to allow air from the main living space to mix with the air in the conditioned attic. He does not install a fan. Instead, I believe he is relying on the stack effect. I'm not sure it really matters where you install the return as long as its not in a bathroom, kitchen or high-moisture environment.
That said, I would suggest monitoring the temperature and humidity levels in your attic.
排气高达possible and sufficient face velocity for good mixing makes sense to me. I wouldn't put the intake right at the ceiling (the air there has more moisture).
虽然代码提供了多种选择，但我确信它们并不完全等同于有效性或能量损失。我希望HVAC空气最有效。
我喜欢史蒂夫的优化理念，基于测量（优选在木材护套）。
E247，
Don't forget the fire safety issue -- building codes forbid exposed spray foam in an attic if there is communication between the attic air and the air in the conditioned space below. For more information, see"High Humidity in Unvented Conditioned Attics."
在那篇文章中，我写道：
"Because spray foam is a fire hazard, this approach [leaving spray foam exposed in an attic] only works if you don’t have any HVAC ducts capable of bringing smoke from the attic into the conditioned space below. Lstiburek wrote, 'The assumption behind the approval of the use of intumescent coatings is that air from the attic does not communicate with the rest of the building. … None of the International Code Council Evaluation Service (ICC-ES) Evaluation Reports for spray foam insulations allow this type of application if there is "real" air change or communication with the "occupied space." Unless, the spray foam is covered with gypsum board. Cover the spray foam with gypsum board? Not going to happen.'
“在这种类型的阁楼中返回空气管道在技术上是违规的代码，而供应空气管道处于一种合法的灰色区域。”
In the comment section of the article "High Humidity in Unvented Conditioned Attics", Joe Lstiburek says (see comment #18):
“显然没有烟雾问题或火灾问题，当管道泄漏时，天花板泄漏到差的工艺。但是当我们有少量供应空气的管道而不是存在漏水管道时存在问题？欢迎来到代码世界。现在，在代码世界中向阁楼提供空气是可以的 - 返回它不行。从阁楼到外面的空气排出，导致阁楼的负压导致空气从房子拉入阁楼也可以。所以我的代码更改在代码世界中都可以。在真实世界中，他们导致更安全的建筑物和一个没有水分问题的建筑物。“
因此，根据代码向阁楼提供空气。如果空气由HVAC供应通风口提供空气，或者风扇将空气吹入阁楼空间，它会产生什么差异？在任何一种情况下，都有阁楼供应，但不是回报。
a）HVAC可能不会一直运行 - 所以它会在不使用时提供更少的CF /日（零）
b）夏季与AC，HVAC空气的绝对湿度较低 - 如此少湿度/ CF
IMO, the most reliable warm weather solution is a dehumidifier (with moisture monitoring to set the humidistat and to alert you when the dehumidifier fails).
我确实有一个独立的除湿器，没有连接到HVAC管道。将一些空气从Dehumidifier排气转移到阁楼空间中是否是更好的选择？
在相同的CFM，它将提供比室内空气更多的干燥。但这可能比需要更干燥。