Pressure pan readings on can lights and exhaust fans
I was testing a house yesterday and took pressure pan readings at some of the can lights and bath fans, while the blower door was running with the house at -50. One story house, flat ceilings, vented attic. The can lights are older style, had a good deal of air coming in through them, and tested at about 45 pa wrt indoors. The bath fans are newer Panasonic models vented to a gable wall with well-installed flex, and tested at about 10 pa. They didn’t have much air coming in, according to my trusty biometric airflow sensor.
Questions: any of you blower door geeks check stuff like this, and if so, what do you normally find? If a fan is +10, is that a fairly low level of leakage, or is there room for significant improvement, perhaps by installing a better wall cap or maybe an inline damper? No doubt a can light at +45 is a major hole to the outdoors, so if I change it for an IC/AT version with an “air tight” trim, what kind of numbers would I be getting? Any other comments?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
We've not been testing cans or fans during the blower door test but have been confirming exhaust rates for a while and the bath fans, even with 6" hard steel duct and exterior damper hoods are often quite under-performing. Strangely, the ones that we use to exhaust air from the crawls through a 4" galv by 20-30' vertical stack up the chimney do surprisingly well. go figure.
Michael, I usually test all the fans and only a few perform near the rated CFM. Those are the ones that are not more than a few feet of straight duct from the wall cap. Anything with more than that is likely to be 75% or less of the rating. Curious to know why you are venting crawl spaces with fans...?
I believe 45pa translates to 90% connected to the outside. 10pa = 20%. Can lights are notorious. You are supposed to box them from uptop. IC rated of course.
我们通常用ICAT外壳代替轻型外壳。与普遍的看法相反，制造商允许您将几乎所有与他们直接接触的东西都放置，因此，没有太多理由在气密性方面不出色。当我们密封阁楼时，我们用CAN泡沫击中了布线穿透和外壳/干墙间隙。
10PA在风扇上并不可怕。粉丝的收获是，他们通过管道和外壳/干墙连接泄漏。再次，作为空气密封的一部分，我们将密封住房和管道。我喜欢Broan的屋顶帽，但是背景阻尼器有点平庸。我已经使用了EFI出售的布背带阻尼器， @50PA效果很好。但是，我的直觉是，在高压力下，布抑制剂可能是有效的，但在大多数房屋中通常看到的低压。例如。获取一块布尼木，并在上面吹。
我们正在完成一个ICF房屋，最近在打击阁楼绝缘之前，用鼓风机门进行了测试。我们将鼓风机的门设置为-50 pa，并使用压力盘记录所有天花板的读数，以及厨房中的四个IC级罐子灯。这些盒子的电线穿透在板岩岩石前密封，但没有一个被填充到板岩上。最初的读数在-18-25 pa范围内，房屋为-50 pa。当我们使用压力盘时，我们还注意到，当每个盒子时，Mantomer上的CFM @ 50的变化通过了泄漏的减少关系。或可以掩盖。我们注意到，根据覆盖位置的不同，CFM读取与压力盘的PA更改相对变化，每个位置约为50 @ 50 cfm @左右。我们正在执行此实验，以便在无需进入阁楼的情况下拥有另一个有用的质量检查空气密封工具，以及一定的压力盘读数的重要性。
Additional information you will want to be aware of is that this 3780 sq ft home was only leaking 850 CFM when we started, which is pretty tight by normal standards. The other thing that was going on was that our insulator was in the attic with Knauf Eco Seal. After the initial readings we turned him loose to seal along both sides of each of the interior walls to the sheet rock and also to fan spray over all of the electrical boxes in the attic. The final result was a 3800 sq ft home that leaked just a little over 500 CFM @ 50 Pa. All in All it was a pretty informative day. By the way, the Eco Seal application would have been around $650 to $800 for the insulator to make a reasonable profit. The product is in the neighborhood of $225 per five gallons and they got well into a second bucket before they were done.