remediating radon in new house, combine with finishing out basement

[semipro]

As an aside, when I hear that someone is building a new house in radon regions I always recommend they install the slab fitting and exhaust piping up to a point below the roof in the attic. It's relatively easy to do during new construction. That way they can install the fan, wiring, and roof penetration later if needed. The end result is much cleaner than the add on systems that usually end up outside the house envelope.

 

[RustyShackleford]

I think he is going to exchange only the air below the plywood? I.e. much less cubic feet?

Yes. I believe the radon remediation contractor (who gave a bid) said the area was about 800 sq-ft. I'd guess the average distance between the plywood and the vapor barrier on the soil is about one ft. So let's say 1000 cu-ft. So 20cfm would give me one air change an hour, roughly, probably overkill given my fairly low radon levels.

Not sure if I need high static pressure one or not - I'm thinking not. I don't see what's wrong with having an intake vent on the other side of the basement, so there's plenty of flow (which, as we discussed before, I can make the opening variable). Seems like whatever radon seeps up from the vapor barrier would quickly get dissipated.

I definitely intend to use PVC ducting. One thing I fail to understand: when researching, people always put the fan outside. Why ? I realize the fans are usually weather-resistant, but why not inside ? I imagine even the weather-resistant ones do not want water to get inside the fan. So since I don't plan to run a pipe up above the roofline, I might just put. the fan inside the basement, then have an elbow pointing downwards just outside. Shouldn't be too tough to change it later, if need appears.

 

[stoveliker]

If you put an intake vent there, then indeed not high pressure. But you'd be cooling the floor there in winter and humidifying a place you can't see/inspect in summer...

Or,.if the intake is from inside the house, you'd be pumping out warm air from your home.

 

[RustyShackleford]

If you put an intake vent there, then indeed not high pressure. But you'd be cooling the floor there in winter and humidifying a place you can't see/inspect in summer...

Or,.if the intake is from inside the house, you'd be pumping out warm air from your home.

Fair enough. I'll get a low-flow/high-pressure fan.

 

[RustyShackleford]

Apparently Fantech replaced their HP series of radon fans with an RN series. Fantech sent me a chart of the correspondence, and said the HP ones are fine. This outfit sells the HP, cheaply, I suppose because they're discontinued:

(broken link removed)

Not sure if this one qualifies as high-pressure or not though. It's supposedly corresponds to the RN2.

 

[stoveliker]

Others will know better, but I find a static pressure of 2" not that great for a system where you have very little flow. Meaning that you have to make sure you have enough (18 cfm) air inflow under the floor or the fan won't like it.
In my uneducated estimation (and I may be corrected here), that's more than I would like under my floor (see cold in winter and humidity/mold in summer).

On the other hand, if you do have enough air inflow under the floor to keep the fan happy (i.e. not overheating), you have a quite a few air-replacements per day. Because 157 cfm (note the per minute!) at 0" static pressure, is, for the space under the floor,a lot of cold coming in in winter/humidity coming in in summer, or heated air from your room exhausted.

Basically I'm not convinced this fan can do what you want.

I see Radon fans with 16" static pressure. This one has only 2" at max.

 

[semipro]

One thing I fail to understand: when researching, people always put the fan outside. Why ? I realize the fans are usually weather-resistant, but why not inside ? I imagine even the weather-resistant ones do not want water to get inside the fan. So since I don't plan to run a pipe up above the roofline, I might just put. the fan inside the basement, then have an elbow pointing downwards just outside. Shouldn't be too tough to change it later, if need appears.

I've seen many systems inside houses but you have to look to find them.
I think the reason you see so many outside is because they are retrofit installs and it's just much easier to do.
There's also your bias in that you don't have x-ray vision.
You'd want to consider noise level when installing inside of course but some of the fans are super quiet. I've stood right next to them and it was hard to tell that they were running.
If you install outside you'll have more penetrations through your outer shell (suction duct and power) as opposed to an inside install where you might only penetrate the roof.

 

[RustyShackleford]

Didn't realize how expensive large-diameter PVC has gotten. Also didn't realize there's a lower grade than DWV called S&D (sewer and drain). Guess I'll use it. Wall thickness is less than 0.1", but if it's good enough for sewage I guess it'll suffice.

 

[RustyShackleford]

Starting to think the way to go is ventilate the space between the vapor barrier and the plywood with an "energy recovery ventilator" (ERV), such as:

Fantech SE704N SE - 56 CFM - Energy Recovery Ventilator ERV - Side Ports - 4-Inch Duct

The Fantech SE - 56 CFM - Energy Recovery Ventilator (ERV) - Side Ports - 4-Inch Duct SE704N has been discontinued. Check out Expert's recommended alternatives for another top energy recovery ventilator.

www.ecomfort.com

... avoiding the pitfalls of sucking excss humidity into that space in the summer, or increasing heating loads in the winter.

 

[stoveliker]

Starting to think the way to go is ventilate the space between the vapor barrier and the plywood with an "energy recovery ventilator" (ERV), such as:

Fantech SE704N SE - 56 CFM - Energy Recovery Ventilator ERV - Side Ports - 4-Inch Duct

The Fantech SE - 56 CFM - Energy Recovery Ventilator (ERV) - Side Ports - 4-Inch Duct SE704N has been discontinued. Check out Expert's recommended alternatives for another top energy recovery ventilator.

www.ecomfort.com

... avoiding the pitfalls of sucking excss humidity into that space in the summer, or increasing heating loads in the winter.

I may be misinformed, but in my understanding an ERV does not prevent (much) the humidity from coming in?
(It does help with the winter heating load issue.)

 

[RustyShackleford]

I may be misinformed, but in my understanding an ERV does not prevent (much) the humidity from coming in?
(It does help with the winter heating load issue.)

From the docs (at that link):

Compact ERV with easy mount wall bracket. Brings a continuous supply of fresh air into a home while exhausting an
equal amount of contaminated air. The enthalpic core at the
center of the unit transfers heat and moisture from the
incoming air to the outgoing air. The air brought into the living area is cooled and the humidity is reduced for maximum
comfort. Reduces the load on a home’s air conditioner to
save on cooling costs.

 

[stoveliker]

It'll do something but the water transfer is not nearly as efficient as the heat transfer, afak. But maybe my knowledge is old and technology has progressed.

 

[EbS-P]

Looks like has some dehumidification. I’m guessing some Peltier type cooler???? It’s has a defrost cycle. So it has to have a drain line right? Can you adjust the in and out cfm independently?