Pipe out through wall or rim joist?
seiyafan
| Posted in General Questions on
I need to get a PVC pipe out from the garage. Can I just simply run it through the wall or does it have to go through the rim joist? What would be the benefit?
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Replies
Joe,
What type of PVC pipe is this? Is it a plumbing drain? A plumbing vent? A flue for a combustion appliance? A radon system vent?
Where is it going?
It's a radon vent using sch 40. I see a lot of professional installed radon system with the pipe going out through the rim joist, but this would involve two extra elbows compare to just through the wall. I am wondering if the reason is due to building code, or something else.
Joe,
Ideally, a radon vent (especially a passive radon vent) should penetrate the roof, not a wall or rim joist. Keeping the vent pipe indoors keeps it warmer, enhancing the stack effect.
If a roof penetration is impossible, you can route the radon vent through the wall or rim joist, and continue the riser up the outside of the building. If the building has a roof overhang -- most buildings do -- the pipe will still need to penetrate the roof near the eaves, and will still require roof flashing. The vent pipe should terminate about 12 inches above the roofing.
If the radon system requires a fan, remember that the fan must be located outside of the building's thermal envelope. If you don't have an attic, your system will either be passive or will require an outdoor fan.
For more information, see All About Radon.
Martin: Why does the fan need to be outside the thermal envelope? I'm about to have one installed and putting it into the radon pipe inside the conditioned space will be much easier.
Thanks.
Stephen,
Q. "Why does the fan need to be outside the thermal envelope?"
A. Because if the radon exhaust pipe downstream from the fan is ever accidentally breached -- for example, by an errant drill bit -- or if the exhaust pipe downstream from the fan ever had a leaky joint, then radon would be introduced into your house.
Martin: thanks
The idea of putting the fan outside the envelop is that the whole of the pipe inside the envelope should be depressurized, so that if it were to leak, the leak would be room air into the exhaust, not radon into the room. With an extremely high soil gas radon level, that level caution makes sense. With a moderate radon level, and PVC pipe sealed well, it's a little paranoid, but there's no harm in following it anyway.
It might be better phrases as putting the fan after the pipe exits the envelope--a design in which the pipe exits the envelope, goes through a fan, and then comes back in the envelope would not meet the intent of this guideline.
In my mind, the main reason for keeping the whole pipe inside the envelope is the hope that you might be able to get away with no fan, using only stack effect. If you are running a fan, the fan will be way more powerful than the stack effect.
Martin: One possible location for the vent pipe will have it terminated approximately 2 feet above the eaves, but it will be within 3 feet radius of two bathroom exhaust vents and two plumbing pipes. Is this still a bad place? The other possible location is on the opposite side of the house where there is only a boiler air intake but it will be 13 feet away.
Joe, our local code (Oregon Specialty Code - Radon Mitigation) requires radon vents at least 10 feet from any operable openings (e.g., window) or air intake, and at least 6 inches above the roof for residences and 12 inches above the roof for public structures. A radon vent close to another exhaust vent is not a problem. But keep it away from intakes, just as you would the kitchen range exhaust or any other mechanical ventilation exhaust.
Joe,
Stuart provided you good advice. It never hurts to research your local code; if you're in doubt, call your local building department.
What about this side wall vent?
https://www.tjernlund.com/radonvac.htm
Seems like a great solution without the need of a roof penetration (I'm trying to minimize those).
Any Options?