vent height

[Greg Keene, CPI]

First time I have seen power vents for the HVAC and DHW made of PVC vented through the roof as opposed to out a side wall. I am assuming they must follow the same rules as draft vents for 3'/2'/10'. Am I wrong?

[mnahrgang]

I don't know the answer per code or installation instructions, but by inference I wouldn't think they would need to follow the same rules...

1) the vent gas is cool so there is no concern about fire or damage to the roof.
2) there is no need for "proper drafting" of the vents since they are power driven.

Like I said though, I could easily be wrong. That's just my thought on it without knowing the installation instructions.

[Jeffrey R. Jonas]

Greg,
I have not seen them through the roof as in your pic either. Normally they are located in the chimney, or out a side wall. Seems to me you will have issues whenever you have snow accumulation

[James E. Braun, CMI]

Yes, the same rules follow as if they go through the roof. I have installed several of them like that without any problems. Some local codes may require it to be above the peak of the roof though.

[Larry D. Kage]

The three flashing boots on top of the shingles is a poor (leak prone) installation, also.

[Greg Keene, CPI]

I guess my main concern was with snow - these vents don't stick up more than 12 inches and we get larger accumulations than that every winter - and you are right, the boots aren't caulked at all - thanks guys -

[Kenton H. Shepard, CMI]

Greg, I see those roof-installed here in CO fairly often, but I've never seen them terminated that close to the roof. I don't believe that they need to comply with the 2-10 rule, which is mainly for adequate draft, but I'm pretty sure that the AHJ defers to the manufacturer's recommendations. I have never seen them comply with the 2-10 rule when installed on a roof. I generally see them terminate around 18-24" above the roof.

I'd be concerned about snow cover too and I'd call it out as needing confirmation of proper installation by a qualified contractor. The exhaust might blow itself free, but the intake might be a problem. As Mark said, they're power-driven, but you don't want the furnace sucking in moisture from snow.