Radon Gas in Crawlspaces & Basements - why is it a trouble?

Radon gas was not high on the radar of builders and habitation owners over the final few decades, simply as it is the 2nd leading crusade of lung cancer (subsequently smoking) in the U.s. & Canada, information technology is apace becoming a household term. Many newer homes will have radon barriers and vents merely the question remains of how to deal with loftier levels of radon in existing homes with no mitigation system in place. Below we outline radon mitigation solutions on a case-by-instance ground, with different options available for different foundation and basement situations. If you but found out you take high radon levels in your home, or you've looked at a radon map that shows your state or region as beingness at adventure of high radon levels, don't panic; at that place is virtually always a way to set up radon gas levels in a home - I should know, my house was tested to have high radon levels, and after radon mitigation was installed and we re-tested for radon, I at present know nosotros can live safely - then radon mitigation works!

First footstep, find out if you have a radon gas problem by having the air in your home tested. A radon testing kit is not very expensive and should be available through your municipality, land, or via a reputable radon testing kit brand online. Y'all ordinarily need to put a radon testing unit on each floor of your business firm and forget about it for a few months; then send it to the lab to larn the results. Testing is better done in winter when windows are closed to get an authentic reading. Normal activeness like doing laundry with a dryer vented to the exterior and running ventilation equipment is to be expected, then yous don't demand to change your normal behavior when testing a home for radon. If you know or suspect that your home is "at risk" for radon, then consider installing a continuous SMART Radon monitoring organization with alarm via a dedicated App - these cost a little more but give added peace of mind and radon gas levels in the home can exist tracked. Click on the epitome below to meet ane option nosotros like, or compare and become pricing on Radon Monitoring systems hither.

If you go a high radon reading in the air, the side by side logical footstep is to determine the source, so get-go check your water for radon to come across if that is the problem; read more hither.

In high radon risk areas, new homes frequently have 'passive' radon mitigation systems installed when they were congenital (a elementary iv inch pipe from below the slab to the exterior), though they have limited effectiveness every bit in that location is rarely plenty stack pressure to draw up radon gas from the soil. They are still skilful to have, generally because they can be adapted to include a fan to draw air if radon levels in the home turn out to be loftier.

Background levels of radon are present everywhere and are usually so low that there is no fashion to know ahead of breaking basis if a building site volition lead to a dwelling house with unsafe radon levels. And as nigh all homes will have at to the lowest degree some radon present, there is no reason not to take the basic steps in the get-go to avoid a harder problem to solve in the future. Having said that, basements are potentially more than decumbent to radon gas issues, so that's some other of the reasons to cull a slab-on-course instead of a basement.

Active radon stack

Active radon stack installation © Radon Works

Radon exhaust stacks - placement to avoid freezing in cold climates

Radon stacks are often brought upwardly through the walls and vented out through the roof like a plumbing stack. The intention of that design is to keep information technology far plenty from open up windows to foreclose the radon gas from re-inbound the abode, but that is unnecessary and can work against you.

The air below your slab is potentially very humid, and in common cold atmospheric condition it'south warmer than the outside air. Equally a radon mitigation system can draw upwards to 2 litres of h2o a day through the exhaust stack, in colder climates this warm, moist air often condenses in the cold top of the radon stack and leads to freezing in wintertime as h2o vapour tin crystallize in the exposed length of pipe extending from the roof and plug the radon stack completely.

Radon vent

Radon vent installation at low level © Radon Works

Preferably, if in a cold climate zone you lot would direct the frazzle vent from your radon stack direct out through the rim joist (as seen in the side by side images), and there are several benefits to this location for all climate zones – information technology is a quicker install with less materials required, you avoid having to puncture your roofing materials and risk water leaks, and only a couple of inches of pipe is exposed to depression winter temperatures if y'all're in a cold climate zone instead of a taller roof stack, so you greatly reduce the adventure of freezing and getting the radon stack blocked upward. It is also easier to throw a quick eyeball on a vent at basis level to bank check for freezing rather than getting upward on your roof in winter, and very much easier to unfreeze your radon stack exhaust if you demand to. Check pricing for Radon Ventilation fans here.

The location of radon exhaust vents can follow the Building Lawmaking requirements for venting combustion appliances, which is to keep them 3 feet from operable windows. Keep information technology further away if you can, only there is enough dilution of air over just a few feet to forestall any noticeable amount of radon from re-inbound the home. And exist mindful to locate it at least that same distance away from an HRV or ERV fresh air intake or even a basic bath or kitchen fan outlet - because when they are off, they could backfeed radon into your home if the conduit runs down into a basement - which would be bad.

Before starting radon mitigation in a crawlspace or basement:

Hither's a thing, if you lot're nearly to install radon mitigation in a crawlspace or basement considering your radon levels are above recommended levels, then the start step to starting the piece of work and installing a radon barrier is to ventilate your piece of work area. Open windows, put in a temporary low level inlet that goes outside at least 5 feet away from the window and turn on the fan for a couple of hours before you lot go working downward there. Safety kickoff, once yous know there'due south an issue with radon in your home, avoiding animate it as much equally possible is a sensible precaution. If you lot accept mold down in your crawlspace or basement too, wear a mask and accept this into account in specifying your radon mitigation solution. Preventing mold when finishing a basement is possible, read hither to find out how.

Radon in Crawlspace floors that won't be insulated:

A radon barrier needs to be installed to seal off the basis from the air in the crawlspace. A DIY radon mitigation solution for a crawlspace is to use a standard half dozen mil polyethylene vapour barrier, which works, simply contractors may be required past law to use a burn-rated membrane. The membrane itself is not impermeable to radon, but radon will take the easiest route, then as long as information technology is an active system where air is drawn by a fan from under the radon barrier, the results are usually quite effective. For extremely high levels and to ensure that your radon mitigation is dealt with once and for all, you may consider upgrading to a radon membrane that is tested impermeable to radon to be sure of satisfactory results from your difficult work.

The radon gas membrane needs to be sealed to the exterior wall (in a higher place the wall is improve if it's below course) and all penetrations from plumbing or structural supports demand to be well-sealed, including the intake that will pull the radon from below the membrane and exhaust the gas outside.

Radon in Crawlspaces that will exist insulated:

The most effective technique for insulating crawlspaces and stopping radon ingress is eco-friendly sprayfoam applied on the footing and walls; for more than details see how to insulate a crawlspace properly page hither. To install a radon evacuation stack along with spray foam, in that location must be some medium in which the air and radon can move effectually below the cream. A layer of crushed stone will do the chore as long every bit the intake is in the stone and non blocked past the foam. Spray foam will continue top of the stone and seal around the stack.

If getting a iv inch-layer of clear stone into your crawlspace is not a viable option, there even so needs to be a consistent separation between the ground and the radon barrier to allow radon to move freely below. This can be washed by installing a dimpled membrane over pinnacle of the dirt, or another such suitable product. If your crawlspace flooring is flat, another option is to utilise a radon resistant ridged layer of XPS but exist sure to carefully tape seams that allows air move below. This will requite yous a bit more thermal protection, and will be air-sealed by the spray foam on height. Past doing this, you will either be able to utilise a bit less spray foam or you lot will have a higher R value and more efficient thermal barrier.

Radon mitigation in finished basements:

If you have a finished basement and have discovered y'all take high levels of radon, don't panic, there are constructive and affordable options.

The easiest and near affordable selection is sub-slab depressurization. Near newer homes would have a vapour barrier beneath the slab, though likely non well-sealed. Some homes will have none, simply in either case, concrete in fairly skilful condition should provide enough of an air barrier to contain radon below it.

A contractor volition drill two pocket-size test holes in the physical flooring on contrary sides of the basement, and then install a vacuum in one and mensurate air flow with the other. If there is sufficient air movement below the slab, then a radon evacuation stack tin be installed with a fan that exhausts to the exterior.

Rob Mahoney of Radon Works in the National Capital Region is a radon mitigation specialist who has had not bad success with this technique.

"We have taken finished basements with radon levels in the thousands of becquerels and brought them down below a hundred using sub-slab depressurization", says Mahoney.

Dedicated HRV for radon removal: if testing shows that removing radon from below the existing slab will not be successful, an HRV unit (heat recovery ventilator) or ERV unit (energy recovery ventilator) dedicated to the basement can be very effective. There is a continuous radon monitor called a Radostat that controls ventilation equipment past activating it when radon levels reach a height 150 Bq. The HRV will kick in to high speed, and once levels have dropped to a safe level, the Radostat returns the HRV to its normal operating setting, and leaves the basement pressurized, which will reduce the amount of radon that can escape from the basis beneath.

Radon mitigation in unfinished basements:

The dedicated HRV organization mentioned above is also an option for removing radon gas from unfinished basements, as is sub-slab depressurization. If you have extremely high levels and the HRV isn't sufficient and you also are not able to exercise sub-slab depressurization, you tin can pour an additional concrete slab on peak of the existing floor or even consider a sidewall mounted self contained radon removal system.

The intention for pouring an additional slab is to create an air-sealed cavity where radon tin collect and be removed. This tin can exist done with a ridged layer of EPS insulation with voids underneath where air tin circulate. A five inch pigsty is cut in the EPS layer where a flange and radon stack are installed. In one case it is all sealed, a new layer of physical is poured on acme.

To use the rigid sheets of insulation you would need a flat surface, so along with existing basement floors, this is possible in a crawlspace likewise if it is flat plenty - though very few are.

Radon mitigation example for when installing a basement flooring, radon prevention is better than a cure

Air sealing betwixt floors to finish radon:

If yous have extremely loftier levels of radon, the Radostat and HRV pick may work well, but might not bring you to completely safe levels. Due to the stack effect of warm air ascension, basement air volition e'er find its style to upper floors to balance pressure as warm air escapes through leaks at the higher points of your firm.

In such a case, you may wish to create an air seal between the basement and upper floors. Very few membranes will actually block the passage of radon; i that does is bachelor here, a membrane that can exist installed either under slabs or in this case, on the ceiling of the basement to split up those environments. This will require meticulous attention to detail when sealing opening, but it tin be a cheaper alternative to pouring a new concrete floor. Nosotros would also e'er recommend fitting a radon monitoring device or system to make actress certain no taped seams have come apart.

A ceiling membrane is a solution that should be used in conjunction with the HRV, so radon-rich air volition not contaminate the upper living floors. The dangers from radon gas are from long-term exposure, so every bit long as you don't use your basement as living space, going downwards to put on a load of laundry in a basement with higher levels will not cause you to drop expressionless on the spot; you merely don't want to live in it constantly.

Important to remember to stop radon ingress:

  • Keep your HRV air intake clean! Blocked air intakes can depressurize the basement and crusade a dramatic increase in radon levels by drawing it out of the soil.
  • Sump pumps do not always take airtight lids, so be sure yours does or y'all will impede the organization from doing its job properly.
  • Radon gas in air is measured in becquerels per cubic meter (Bq/m3) in Canada, and Health Canada recommends taking steps to mitigate radon in homes when levels exceed 200 Bq/m3 . Radon test results in the USA may be reported in three different measures – picocuries (pCi/fifty), Working Levels (WL) and bequerels (bq). If your exam result is in pCi/L, EPA recommends you fix your home if the radon level is 4 pCi/Fifty or higher. If the test issue is in WL, EPA recommends y'all fix your domicile if the working level is 0.016 WL or higher. Some states crave WL results to exist converted to pCi/Fifty to minimize defoliation. While non usually used in the United States, any radon level at or to a higher place 0.148 bq should be reduced - pointing out that the EPA recommendations are lower than those in Canada. Also interesting or potentially worrying to note is that the Globe Wellness Arrangement WHO sponsored International Basic Safety Standards (2014) and the IAEA Safety guide on radon (2014) recommended annual boilerplate concentration reference level is 100 Bq/m3 - one-half the Health Canada recommendations. As the WHO puts it: "The lower the radon concentration in a dwelling, the lower the risk of lung cancer every bit there is no known threshold below which radon exposure carries no risk."

The radon mitigation techniques discussed hither are intended to give homeowners an thought of the types of solutions that are available for reducing radon levels in homes, they are not intended as a DIY guide. Radon contagion in homes is a serious wellness business and is best handled by an experienced professional person who can guarantee results.

 "At that place are countless air sealing products available on the market, yous just demand to know which ones to apply and how to use them finer. At that place is always a solution for reducing radon levels; yous but may need to exist creative about it. The worst case we always found was a home with a reading of 20,000 Bq /m3 and we were able to bring information technology down to under seventy." – Rob Mahoney.

That covers Removing Radon gas from Crawlspaces & Basements, to read more aboutRadon Mitigation in Homes, run across the Guides here, to read how to reduce Radon Gas in well h2o, see here, both from the EcoHome Greenish Building Guides

Rob Mahoney is a radon mitigation specialist in the National Capital Region and sits on many advisory boards including the Canadian Association of Radon Scientists and Technologists, Canadian National Radon Proficiency Program, Canadian General Standards Board and CGA Standards (Compressed Gas Association). He worked with the CHMC on a radon prevention airplane pilot program and helped bring radon prevention into building codes. A big thanks to Rob for his technical guidance with this page. To larn more than about radon prevention measures, visit his website radonworks.ca.