Before I dive in too deep, I just wanted to dummy-check and ask: should an HRV help (in theory) lower radon levels in a home?

We have a radon system installed, and it brought down the levels considerably. Currently the basement still reads between 3.5 - 5+ (it used to be in the teens...). The radon system is plastic sheeting with perforated corrugated tubing and a fan drawing air out. It's an old house, and the system isn't - and can't be - 100% airtight.

I'm wondering if pumping some fresh air down there (and to other areas of the house) will help lower the levels even more. The time and money should be at least as effective as efforts to get the radon system to function better. It would also be nice to have fresh air coming into other living areas as well.

The plan is to supply air to the basement and draw air out from the top of the stairway leading to the basement. In general, the radon system tends to pull air down the stairs, so there should be some mixing, but that's fine. I'll also supply to the main floor bedroom and maybe another spot or two, and draw air from the bathroom on the main floor.

Thank you for any thoughts you have.

You should under 4, ~ 5 ish may not be a big deal. Why not increase the CFM of the mitigation fan? That’s the best place to exhaust. Fresh air IF it is outside you home is probably being pulled in from above grade band sill cracks and exhausted out too unless it is sealed.

It’s depressurizing your basement along with stack effect delta T and higher temps upstairs if the AC allows it so small flow down stairs makes sense if the mitigation system is over powering stack effect.

You might try a test. Make sure there is no up/dn Delta T open the basement windows run an low flow exhaust fan up the stairs to open windows check the levels at various locations up and down. Note the highs.

If that proves positive and the radon is being diluted dropping levels, you could install a small ventless downstairs like LUNO, ZEHNDER, or Vent USA in your band sill making sure the basement and other poor IAQ areas are slightly depressurized. That should reduce stack effect and increase up IAQ too but make sure you use the exhaust fan when cooking and baths.

A whole house system makes most sense in air tight construction < 1 ACH@50, otherwise, you should be getting natural ventilation. Not sure how much of an issue that is w/o knowing your climate. In any case use ASHRAE 62.2 to size the systems if you go this route not mfg data.

Thanks PARAHOMES. I should mention I'm in Western CO around 5,700 feet.

I asked the radon guy about a stronger fan, and he mentioned concerns about backdrafting the boiler and water heater. I'm not sure if he's being extra conservative, but always better to be safe than sorry I suppose. He's not trying to sell me an HRV - this is my own wild idea.

I was also hoping to add filtered fresh air to the house. Looking at a Fantech Flex 100H, they say I can put some extra filters in as long as the unit is oversized for my house and I keep the filters clean. We have "ditch burning season" around here every spring and some neighbors who burn who-knows-what (besides coal - I know the guy across the street heats with coal...).

It's a 1200 sq ft house (plus 300 finished basement) so I've seen that 45 CFM should be sufficient. The Fantch is supposed to work for quite a bit more than that. I like the ventless options but I haven't wrapped my brain around how to make one work in the basement (going through the rim joist). Not saying it can't be done - I just haven't figured it out yet. That said, the plan of running insulated ducting through the attic isn't perfect either.

The testing may be over my head, and I don't know if there's anybody within 50 miles who can do that, but it would be nice to get somebody over here to do that.

Thanks again.

Hartman, I own property in south central CO (near Westcliffe), so I have been looking at radon issues prior to beginning building. (definitely cheaper and more complete if done prior to construction). Since radon is heavier than air and "puddles" along the floor, I suspect an HRV would not lessen the amount of radon. Radon will go through cement. All the radon reduction systems I have read about are beneath a vapor barrier. If your reduction system does not eliminate the radon, the radon is leaking in from somewhere.

Although, HRV's definitely help improve the air quality (hence a good thing), it wouldn't hurt to install one and then measure to see if the radon levels drop. I think the radon kits for measuring radon levels do not work outside (prior to construction), so perhaps good air movement will reduce the radon somewhat.

Thanks GaryO. Yes, if you've got the chance to build in a system (or the option to have one) that sounds much better. There are plenty of places for the radon to sneak through at my house: the cement basement floor, cracks in the foundation (some of which I've sealed), etc.

I'm thinking I will do the HRV because we'll get some benefit from it even if the radon level doesn't drop much, and I only need another 1 or 2 pc/l movement anyway. I've done about as much damage as I can do in the crawlspace, so I'll try getting some fresh air. Good luck on your build.

Well an interesting question you posed here Hartman & under lots of debate & controversy as HRV/ERV have been ever since they hit the market. We don't find any reference to using them as radon mitigation in ASHRAE 62.2/1 & I doubt you find any mfg claiming they are radon mitigation devices, however, a simple internet search shows success stories in basements, I'll contradict myself here since that means pretty much zip to you or anyone else with other variables.

We know from HS physics gas laws like Boyle's that, if temperature remains the same pressure and volume are inversely proportional, so, if the size of your basement is different than another it can't be used, and temp, and flow, and other chemical/gas factors. In other words, it is complicated and so is the answer to your questions would need a building scientist to answer properly as the case with any physics. That is why I suggest you keep up/down temp the same and conduct a flow test.

What we do know is moving air CFM generally works as seen by successful (some not so) mitigation systems and the basic reason they work has to do partial pressures(flow rates) and volume(basement/duct size). The fan air flow generates a low partial pressure stream, since flow is inversely proportional to pressure in a container like a basement or duct there is a pressure drop as flow increases. Making it more complex, the weight of gas we all know radon is heavy or it's "atomic #" is higher at work attracting to where an opening is in the gas flowing we call "air" but it is a complex gas too, to come to equilibrium and partial pressure with....these are the biggest reason and ionic attraction and why radon systems work & they can suck radon out of the ground with the aid of a fan and floors depending on those variables.

I suggest you get your flow rates from the formula in ASHRAE 62.2 where all that has been tested. There has been much controversy about those rates being too high by BSC and causing back drafts as you mentioned. You'll want to seal those penetrations up and install back flow valves. If you take the ducted route make sure you get a good HVAC pro to balance the system. Here is a good resource for selecting CFM based on power consumption or COP and make sure you buy HVI certified: http://hvi.org/proddirectory/ pick the blue #3 icon.

Carbon filters do not remove radon or carbon monoxide form burning or brown fields. You'll want to follow ASHRAE and conduct a outdoor test for placement of intake. As you seal the house they can become more of an issue taking longer to exhaust and if you do not design the system correctly your radon levels can go up. You'll want to be careful lung cancer is the penalty for error. Many just throw HRVs in not following spec or protocol only to make IAQ worse and not know it since toxins can be odorless and not seen. The other hazard is people don't understand what partial pressures can do to drying of the envelop and in a short time end up with mold. I have a client now that is the case.

That's why I suggest you conduct a test before incurring the expense of an HRV by mocking up cross-flow ventilation and seeing if the stream dilutes the radon. That can be as simple as putting low flow intake/exhaust fans in basement windows, further, if you open windows and exhaust only, if your levels drop that is a good sign. The best place to dilute is downstairs not allowing lower pressures up to move radon streams up at the same time not allowing back-drafts.

Last I talked to LUNO couple weeks ago they can't keep enough on stock selling like crazy. I was baffled how many are installing them I guess for the same reasons as you to not have to rely on natural ventilation passive house or not. I found LUNO to be very expensive but you don't have to run ducts and they do a better job at balancing having less effect on combustible back drafts since the units are paired or reverse flows periodically. They also have a split system single unit only need one bored hole in your rim.

Probably more than you all wanted to know Good luck to both.

PARAHOMES what is LUNO? A search got me mostly wrist watches.

heat recovery ventilation:

https://foursevenfive.com/product/lunos-nexxt/

So, stupid question about those LUNOS (and similar) models: do they work in finished basements? My rim joist is "hidden" by a drywall ceiling in my basement, except in the crawlspace. Even if I made a little pocket for the LUNOS, I dont' think the air would circulate very well (because it'd be up in that pocket, and in between floor joists on each side).

I could go through the foundation, but I'm hesitant to do so, and the exterior vent would be too close to the ground anyway.

I'd love to be able to do a ceiling mount in the basement with those types of ductless models (partly because they don't require a condensation drain like other HRVs do). But that would require ducting both the intake and exhaust, and I'm not sure if that's possible.

If your pCi/l levels are already in single digits you have more important things to worry about than bringing it down to under 4 (which is an EPA recommendation, not a regulation, in part because there isn't sufficiently good science to support it as a rationale for regulation.) You get a bigger up-tick in annual radiation burden from living at 5700' vs. sea level than from low-radioactive air at 5 pCi/l vs. 2pCi/l.

While it's not worth spending money on HRVs to lower the radon levels, it's probably still worth spending it to reduce the risks from other indoor air quality issues. But over-ventilating in high-dry Colorado can lead to wintertime comfort problems, with it's own set of health risks (eg, airborne virus transmission, etc.) Don't go crazy on ventilation rates just to duck under some magic radiation level of indeterminate risk.

The EPA recommendation is from a theoretical risk based on estimated miner doses at more than 100x the EPA recommended mitigation levels using a linear extrapolation, which is flawed at best- radiation doesn't have linear risk at such low levels, and there is some evidence that levels of a few 10s of pCi/l may even be protective (lower risk than 1 pCi/l), though it's difficult to separate the risk signals from the noise at those low levels. In large cohort epedimiological studies lung cancer risk is in lower in high-radon counties of the US, and higher in low-radon counties, even when controlled for many other known risk factors. In the state of Kerala India the naturally occurring radiation (including radon) from the large amounts of thorium bearing sands give the average citizen more than 50x the annual radiation you are experience, yet they have the longest life expectancy in the country (~75 years- which is pretty good for a third world country), and among the lowest cancer rates, despite that longer lifespan. In the villages there are much higher health risks from cooking smoke, and in urban areas, it's from diesel emissions, not radiation.


That said, a 2000' house (with an 1800' basement) in my neighborhood measured ~30pCi/l in the basement 12 pCi/l ion the first floor before they installed a Lunos E2 (about 20cfm at max speed). The Lunos brought it under 15pCi/l in the basement, under 9 pCi/l upstairs, a which point they opted for the smallest radon fan available for slab depressurization. That brought it to ~3pCi/l upstairs, ~8 pCi/l in the basement, and they're calling it "done". They drilled through the poured concrete walls to install the Lunos about 15" below ceiling level, not the band joist, and they have to pay attention to keeping it clear after snowstorms. I'm don't remember what the recommended minimum clearance to the ceiling is with that HRV (even though I have a pair in my house) but you won't get sufficient air exchange if it's tucked up at the ceiling in a corner.

Thanks Dana. I am a bit of a "worrier" so this is good perspective.

At these low levels the stress of worrying about it is probably a bigger risk than the radon levels. More perspective:

In Europe the regulated level for air radioactivity in new construction is 6.7 pCi/l, based on similar linear extrapolations from underground mine workers to estimate risk. But health risks from all sorts of factors aren't really linear, particularly at low levels. (eg: Daily injestion of large amounts of alcohol has serious health consequences, whereas the exposure to daily glass of orange juice doesn't, and 4oz of wine per day has some measurable health benefits.) The European standard level is more than 1.5x the EPA recommended mitigation level, but is also a level way too low to measure the risk directly.

In the US the OSHA regulation (an actual regulation, not a recommendation) for mine workers requires keeping it under 100 pCi/l.

That is fully 25x the EPA recommended limit, and in an environment where the exposure will be much greater due to higher respiration rates. You won't breathe in anywhere near as much air per day/week/year while binge-watching "The Good Wife" on the couch or sleeping, eating etc as someone doing hard physical labor in a mine. The 100 pCi/l OSHA limit is based on more directly-measurable increased risk at levels 2-5x that high, and is still pretty conservative. The aggravating factor of the dust levels in mines may also be an amplifier, but that's also very difficult or impossible to tease out of the data.

Even if the unmeasurable cancer risk increases by dropping it from 25 pCi/l down to single digits, that increased risk simply can't be very much, and if it keeps you from worrying about it it's "worth it". But it's pretty silly to spend money taking it from 4.7 to 2.1 or whatever- the true risk is still "in the noise", and lowering it may even be moving in the wrong direction.

The EPA & European standards are based on the postulation that where radiation is concerned there is no threshold limit, and even tiny exposures increase risk. But that postulate isn't (yet, if ever) a scientific fact, and large cohort population statistics (such as Kerala, India, or Bernard Cohen's study of residential radon by county relative to cancer statistics often hint that there is something else going on at these low levels.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3315166/

These studies have their own deficiencies and don't necessarily "prove" that higher radon levels improve health outcomes, but they are too large to be ignored completely. These sorts of studies are part of why the EPA recommended levels are only suggestions, and not regulation. They strongly hint that the linear extrapolation from health risks to miners at 100x or higher exposure levels probably isn't a very good model.