Second time I’ve seen the now in new construction. What’s the purpose of this mech fan in this attic? It’s switch controlled.
I like that it’s there for selfish reasons - seems like a good chance there’s still toxic VOCs up there from the foam off-gassing, so I’ll let that run or a minute or two…
But are there any concerns regarding the spray foam sealed attic space? My understanding is that the attic should be unventilated with foam.
It should be treated as a conditioned part of the home. That said, it may not be a bad idea to have the vent fan that you can control with a switch. I kinda like that.
My first thought was that it might be tied to a CO detector, but that is an electric furnace. Then I found this:
Wow, love that. The guy’s an HVAC pioneer.
I don’t have the same smart tech here though, and the roof vent doesn’t look like it has a damper.
Would you guys recommend the builder put a vent with a pressure actuated damper on there? The fan might be counterproductive, unless it’s constantly running or the home owner frequently goes up there to use it, right?
If it is a typical bathroom fan, it likely has a built-in damper. They are not the greatest, but should suffice in this application.
Any guess what proper humidity levels look like in a spray foamed attic? I’d like to give my client a number to shoot for, in case he wants to monitor the humidity levels and make use of that fan.
I would say keeping it on the dry side would be best. 30-45% should be ok. Not a huge deal if it gets to 50-60% short term during the most humid months though.
Encapsulated attics, just like crawlspaces should be conditioned. Was there a supply duct?
I didn’t notice a register in the attic, although the pull down attic ladder doesn’t seal tightly.
I call out spray foam attic that is not conditioned. The vent fan is a poor substitute in my opinion. This attic will perform poorly is my bet.
With the HVAC in the attic, it would be fairly straightforward to add if needed.
I just noticed in your 2nd picture, there appears to be static turtle vents on the roof. What are those all about? Are they open into the attic?
What are those all about? Are they open into the attic?
The one on the right is the termination of the exhaust fan, presumably. The one on the left is ventilation from another portion of attic space that was not foamed.
Was the other portion (not foamed)
isolated from the foamed portion with an insulated wall?
What is this? I don’t believe I’ve ever seen one.
AC zone control?
That was what I was thinking, but wasn’t sure.
Yes, seemed to be. insulation and vapor barrier.
It looks to me that this roof was insulated after the HVAC was already in place. Initially it could have been an attic exhaust fan and then they sprayfoamed everything and the fan just stayed there.