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Community and Q&A

No ceiling/roof penetrations, can I vent out side walls?

rkymtnoffgrd | Posted in GBA Pro Help on

Zone 7, 10k in Colorado Rockies, 150sqf snow load.  Standing seam roof.  Due to problems air sealing and snow/ice pressure, I would like to eliminate all ceiling and roof penetrations on my new build.  All electric appliances + heat pump.  Only vents necessary are plumbing and HRV.  I’ve heard mixed feelings if this allowed or not.  Advise is appreciated.

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  1. Expert Member
    AKOS TOTH | | #1

    Depends on your local code. Ours allows for side venting of plumbing provided it goes above the roof but only for renovations.

    Plumbing vents are not like a chimney, they are easy to air seal properly. I would not worry about it. If you are planning for solar, just make sure to put it on the side where it won't shade the array. Even a small amount of shading can destroy the performance of a single panel/string.

  2. onslow | | #2

    Rocky Mtn,

    I believe the plumbing code is a state level function in Colorado. The local county you are building in might have some additional requirements though, so best to ask first. I did my one required plumbing vent out a side wall despite fussing from the annoying plumbing contractor. I was told that the code at the time did require one run from the laundry to be open air vented, so I confirmed at the time that a side vent was okay. I also went entirely with AAV's throughout for all showers, toilets, and sinks despite fussing from the same annoying plumber. Times and codes change, check to be sure of current code.

    That said, I am very happy to not have any penetrations of my roof materials and not be faced with the possibility of leaks or snow capping. My snow load is only 60lbs., so I can imagine that at 150lbs. you would be planning on very deep snow. The taller vent pipe would be that much more likely to frost over and plug as the warm moist vent air ascends into the cold end of the pipe where it can choke off with frost. My side vent is warmed by virtue of being in a conditioned "attic" until it passes through the 12" of wall insulation. So far, so good. I have also found the bath vents to be performing well so far, partly due to exiting from the conditioned space to the outside wall face. Very little chill time is experienced by the warm moist bath air. With the deep snow potential you face, a roof mounted air vent would be madness.

  3. Expert Member
    Michael Maines | | #3

    HRVs usually vent through sidewalls, so no problem there. If you are on the IRC code, they allow plumbing vents to exit through the wall, with a few fine points: You might be in a place where the 97.5% design temp is 0°F? If so, the vent will need to be protected from freezing. Otherwise it just needs to be at least 3" wide so frost won't occlude it.

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