Radon fan in cathedral ceiling
stephenr
| Posted in General Questions on
Hi, I have a vaulted ceiling and am installing a passive radon system beneath my concrete free slab using standard methods (new construction). If my radon test fails I will need to install a fan. In my situation, with no attic, is an above roof fan the only option?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
stephenr,
An inline duct fan isn't too much larger in diameter than the pipe it serves. I would find a spot for one now an make sure there was power available for a future install.
Edit: see Kyle's post #6 below
Thanks Malcolm. Any opinion on the 4x6 load bearing question I recently posted?
stephenr,
The ramp is one of those questions I'm loath to weigh in on from a distance. It's easy to calculate whether the ramp can take the static load of the skid-steer but I'm wary of saying how it would react to the vehicle's movement - and beyond the sizing of the beams, we don't know a lot about how it was built, how high off grade it is, etc. Sorry not to be of more help.
I don't think an inline duct fan is going to be able to draw much pressure. Regular radon fans can usually pull a few inches of water column or so. You might not be able to get enough suction with a simple inline duct fan.
Bill
Bill,
I meant one of the purpose made inline radon fans.
Note that the fan should not be installed inside the conditioned space. It's important for all length of radon pipe inside of the conditioned space to be under negative pressure rather than positive pressure.
Otherwise if there is ever any damage to the positively-pressurized section of pipe (d0wnwind of the fan) it could send air containing very high concentrations of radon from under the slab directly into the living space. This is the reason that radon fans are commonly installed in vented attics.
For vaulted ceilings, in my area it's common for the fan to be installed on the outside of the house near ground-level with the positively-pressurized section of pipe running up the outside of the exterior wall. The aesthetics aren't great but it wouldn't be too difficult to build an enclosure for the fan and then paint the pipe to match the siding.
Here's a worthwhile article:
https://www.greenbuildingadvisor.com/article/all-about-radon
"Radon exhaust fans should not be located within a home’s conditioned envelope; all pressurized lengths of pipe need to be outside the home’s conditioned space. (Here’s why: if the vent pipe ever develops a leak, you don’t want the fan to send radon-rich air into the home.) If it isn’t possible to install a fan in the attic, consider installing it in the garage or on the outside of the building."
Kyle,
Thanks. I had not thought of that or seen it in any of the guides.
Generally, the best system design is to locate the fan outside and above of the living space so there is zero chance that a leaking pipe could blow radon into the living space. This puts all the pipes under vacuum so nothing can leak out only in to the pipe.
You could build a faux chimney in the roof to hold the fan.
I am not a proponent of cathedral ceilings they almost always have 10 pounds of stuff crammed into a 5-pound bag. This radon pipe is displacing insulation and most cathedral ceiling are struggling to meet code minimums. If at all possible, find a different location for this pipe.
Walta
For what it's worth, with reasonably airtight houses, a high-quality, 10-mil vapor retarder with all edges sealed, and a 4" radon loop and riser through the roof near the ridge, I have not yet found it necessary to add a fan, and I'm in a fairly high-radon area.
If you're still in design stage, to be safe, I would locate the riser in a place where a fan could be added if necessary.