Random Radon Thoughts...

Weezbo

however...the pumping it out the roof method it is.you probably have the pipes under the slab and the extra spendy vaporbarrier for radon..so i will toe the party line on it buh not without suggesting leading it down away from the house makes more sence to me ...

Constantin

So I did some exploring yesterday...

... in the semi-finished attic (idle curiosity). I found a couple of issues that I hope are easy to resolve, but the Radon pipe will, most likely, be the most bothersome.

Specifically, our dear HVAC contractors decided to build up their air handler right in front of it, so there is little to no access to that area. The pipe didn't get capped either, so all the delicious and nutricious sub-slab cellar gases are currently venting into the conditioned space of our attic. Brilliant.

The question that lies ahead is how we will deal with the Radon pipe. In an ideal world, one would be allowed to tie into the DWV stack. This would minimize roof penetrations, though I have a nagging suspicion that the powers that be would frown upon such a practice?

If that is not possible, I am inclined to cap the pipe until we can test whether we actually need the added benefit of a Radon mitigation system. If the HRV's produce enough dilution air (as I suspect they do), then I guess we have a nice 4" PVC chase to route new stuff through the house with.

What do you all think?

Fred Harwood

Sub slab gases

The radon issue has been greatly politicized, which doesn't help you, but the facts show that the dose matters, especially in those few areas of the US (such as in Reading, PA) where high levels comparable to uranium mines are found. Get the gases tested if you are worried.

However, much moisture also originates from under the slab, and that moisture should not be allowed to condense anywhere inside the housing envelope. Definitely get it vented outside of the building envelope. Can't comment on connecting to existing roof stacks.

Cosmo_3

Hey Constantin

As far as connecting to you plumbing vent system, that's a nono per code. This may be easier said than done but run it through the roof, even the gravity air circulation will mitigate gases somewhat- Radon, methane, Tremor creature flatulance, etc. You can do your own Radon test to find out if you have radon, most local Home Depo's, etc. have them on the shelf...


Cosmo Valavanis
Dependable PHC Inc

Constantin

Oh, I know I have Radon under the slab...

.... I tested by putting the sample containers into the collection pipe under the slab and capping the pipe. The result: 220 PiC/l, i.e. 50x+ the legal limit. So there is Radon down there...

My addled brain seemed to recall that Radon stacks could not be tied into DWV stacks, but I thought I'd get confirmation, as none of the Radon documentation I have on hand mentioned what is or what is not possible. A common-sense approach would allow the combining of stacks above the last vent connection, but I can understand the fail-safe approach.

I may cap the pipe in the attic, test the house and then elect to bore through the roof if the house exceeds the 4 piC/l limit at that point.

Al Letellier

radon

Cap it and get a test done before you proceed. Don't tie it into the plumbing stack...that's a no-no. a snow clog on the roof could vent sewer gases into the slab.


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Cosmo_3

Well if ya know

Yeah, if you know you have it then you might as well start figuring out how you are going to get thru the roof, other than the clearance around the a/c unit in the attic.... I bet it is a 12/12 slate roof huh....LOVE those.

Cosmo Valavanis
Dependable PHC Inc

Gordy

Radon

Constantin,
I say if you have a sub slab system in place use it. Don't hook it into the DWV though. I recall a fan implemented in the stack of that type of system.Also stack needs to be as close to the ridge as possible and 10' min. from eaves,windows,doors,ect.Radon gas is heavier than air so it is possible for it to re enter the home through open doors, windows before being carried away to the neighbors by wind currents.

Radon readings are usually all over the place depending on time of year,rainfall, ventilation,ect. I bought a electronic test unit to constantly monitor. I have had readings from 4 Pc/l to 12 Pc/l in the basement. Always a 2 or less on the main floor. Since I don't have drain tile a sub slab system is not to feasible for me without some serious work involved.

There is a product called "Radon Seal" thier web site is chalk full of good information. If your basement walls,and floors are exposed concrete, and you want to abandon your system this could be an alternative to seal the radon out.

Personally I have mixed feelings about the invisible gas. For all the propaganda out there by the EPA and I live in the red zone on the EPA map for radon. There is no building codes to mandate radon mitigation in new or old dwellings in our area. Very few people even realise the threat exists. I would think there would be a little more effort for public awareness. I only stumbled acrossed it in my search for a silicate concrete sealer to moisture proof my block walls from the inside of my 50's home.

The prior residents of 40 plus years did not die from lung cancer,although they did not dwell in the basement for 8 hours a day. As with all radiation time exposed, and shielding are the key to protection. I'm not saying radon does not exist nor is it not a health threat.

Gordy

jerry scharf_3

just a thought

Constantin,

I don't have a picture, so I thought I'd ask. Is the HRV anywhere near the radon pipe? If so and you are willing to run the HRV synchronized with the radon fan (never run the radon fan without the HRV) then you could duct the pipe into the exhaust side of the HRV and use that.

Contractors can do the damnest things when not being watched. I haven't decided who is worse yet, plumbers running DWV or A/C people installing ducts. I always remember the post that I think Dan Foley had of the house in DC where the A/C ducts ran across the hallway exposed.

jerry

Larry Weingarten

Constantin, a question.

If your radon pipe is going to have an exhaust fan on it, why do you need to go through the roof? Why not a gable end or other side penetration? Are you trying to avoid leak potential or visual clutter? Both?

Yours, Larry

Constantin

No Gables, No ends, and...

...so on. The house has a mansard roof that I'd like to penetrate as little as possible. After all, every penetration is a likely leak point. The visual clutter is another issue, but a smaller one...

Radon regulations do not allow the vent to be lower than the roof nor to be within 10' of windows, intakes, etc. In other words, you pretty much have to run a pipe to the highest point of the house and penetrate there. We ran the pipe alongside the masonary of the chimney, which ends pretty high up.

The Radon literature does advocate passive systems as a first step before resorting to inline fans. The idea being that if the radon pipe runs through conditioned space that the stack effect will evacuate the Radon from below the slab. How this is supposed work in the summertime is a bit of a mystery to me but perhaps there is enough of a ΔP to get the job done even then.

Constantin

No sewer gases into the sub-slab?

...it wouldn't surprise me if I had to maintain decent sub-slab AQ...

:-)

Constantin

Thanks Jerry!

For now, I have myself fairly convinced that a simple, passive system is as much as I need. Basically, when we ripped out the basement and laid a new foundation, I ran 4" perforated pipe through the 12" crushed gravel that ended up under the slab.

We attached a 4" DWV pipe to the stub that came out of the basement slab and ran it alongside the chimney up to the attic. Said DWV pipe was installed air/watertight with the usual glues. Thus, even if I ran a blower, I guess one could consider it and the blower to be virtually outside the conditioned space of the house, i.e. no interacttion with the HRV.

As for the snafu, oh well, it's par for the course. At least they left enough space behind the AH to continue the pipe upwards, if need be. The question is where we can find a trained capuchine monkey to squeeze through that space to install a pipe. Hopefully, the rubber cap/gasket will be installable...

For now, I'm going to cap the thing up there, distribute several Radon kits throughout the house and see what happens. If the Radon levels are still too high, I'll simply bite the bullet and deal with the potential leaks that any roof penetration entails.

Gordy

sub slab system

The whole concept with a sub slab system is to depresurize beneath the slab, hence the function of the inline fan. The ultimate as mentioned would be to synchronize your HRV with the inline fan. With most homes having negative pressure at one time or another, passive systems are hit and miss. A better passive approach would be to seal the concrete with a penetrating vapor type sealer,and caulk cracks with a urethane type sealant that alone will drop readings more than you think. To add to the passive approach all fuel burning appliances have outside air intakes. The HRV then only needs to compensate for the bath exhaust fans,kitchen exhaust fan,and your radon mitigation fan.

The bottom line is to start out with the simplest, and easiest approach and see how it effects readings and then step up if necessary from there.

Gordy

Constantin

Thanks Gordon!

I meant to reply to your excellent post earlier... I am going to go for the sealer. We'll coat the floor, cap the pipe, and then see where the radiation levels are in the basement. Thanks for the link!

As for the HRV's, they are the bathroom fans... Our only "hopeless" situation is the kitchen fan. Not much we can do there... 1400 CFM! We are attempting to compensate a bit by opening a dampered vent into the AC return whenever the kitchen fan comes on. The damper duct losses are hopefully acceptable...

Thursday is the big day, a.k.a. the first blower-door test.

LKE

more random thoughts



The most effective mitigation strategy seems to me to provide a means of positive envelope pressure at all times.Some electronic controls that sense differential pressure and speed controls that independly vary the speed of the fans of the hrv might be one way to accomplish that.If the basement could be isolated positive pressure their alone could absolutely quarantee that radon gas will not enter the space.
It is not the radon gas itself that is the health threat, but the daughter products that can cause exposure to radiation. Radon has a pretty short half life and breaks down into other radioactive elements, which are toosmallto be respirable but they readily attracted to dust particles that are respirable and could end up in your lungs and if enough of them end up their the dose may be a significant risk for cancer.It would seem then that the next best mitigation strategy would be to control respirable particles by use of a high efficiency particle arrestance filter (hepa)controlling 99.97% of particles down to three tenths of a micron. This mitigates the health risk if not the radon which is the real concern.

Gordy

Positive pressure

LKE, Although you are not wrong in your thinking. A positive pressure system costs money and natural resources to operate. It would be hard to maintain positive pressure 100% of the time.

Start out with a passive approach and see how this effects the readings first. Sealing with a radon sealer product which prevents vapor from penetrating through the concrete and sealing all cracks and creaveses with a urethane sealant is a one time operation, and walk away. Also by sealing the concrete you cut down on the dust. With a sub slab system as Constantin has the use of an inline fine "depressurizes" beneath the slab. If you can get away with stack effect instead of a fan great. But as Constantin stated what happens in the summer.

He already has a Hrv that he uses anyway so dilution will be part of that process.

Gordy

Gordy

Walls

Happy to help Constantin. That site is a jaw dropper if you never knew a thing about Radon. At first I thought it was Biased because of their product, but surf a little and the info is all accurate.

You would probably want to do the walls also. I suppose you could just do the floor, and see how it helps alone. If your foundation was water sealed from the outside it may not be necessary. Definitely caulk where the floor meets the wall though. Do a Radon test before and after. Not in the pipe either,thats kinda like sticking a CO meter in the boiler flue.

Gordy

LKE

postive pressure

The idea of having positive pressure is a way of assuring that there is no negative pressure, very little positive pressure is needed so the idea that it would neccessarily use a lot of energy or resources would not be true. This system has been tried and tested and found to be extremely effective.I read about it in Fine Homebuilding some time ago.The gentleman who built it didn't even have a concrete floor in all of the basement or crawl space being mitigated, there was gravel so no way to seal it up. If I remember correctly this home was in Idaho, and the builder or owner won some kind of award for how effectively this worked, national or state I'm not sure which.