Radon Mitigation: Lowering the Level of Radon Gas in Homes and Buildings

Radon Gas is a silent killer. Recent studies have confirmed the EPA and Surgeon General estimates that as many as 20,000 lung cancer deaths are caused each year by radon in the United States. If your home or building has tested high for radon, the EPA recommends radon mitigation.

What is radon mitigation?

A properly installed radon mitigation system lowers the amount of radon in your home or building, making it as safe and radon free as practically possible. This can be accomplished in several ways depending on the construction of the home or office building. Generally a radon mitigation system is referring to an "active" system or one with a radon fan. There are also "passive" radon systems, those without radon fans, which usually rely on ventilation and sealing.

A basic overview of different ways to reduce radon in your home are discussed in EPA’s “A Citizens Guide to Radon: The Guide to Protecting Yourself and Your Family from Radon". You can get a copy from your state radon office, or view a PDF copy by clicking here: PDF copy of EPA's "A Citizens Guide to Radon"

Click on the picture below to view a video on how a radon mitigation system works.

Source for above picture and video: Pennsylvania Department of Environmental Protection, Bureau of Radiation Protection. A Good Radon Mitigation System Can Greatly Reduce or Eliminate the Danger of Radon in a Home.

However, a poor mitigation system that does not lower the radon level sufficiently is almost more dangerous than none at all; because it can give a false sense of safety. Many people wrongly assume since there is a radon mitigation system the radon problem has been eliminated, and far too often it has not. The EPA recommends that homes with active radon mitigation systems be re-tested after the system is installed and every two years thereafter.

Danger Occurs When Radon Laden Air Is Inhaled or Ingested within a home, office, school or other building, it can then travel throughout the body where it is known to cause cancer and has strong links to Alzheimer's, Parkinson’s and other neurological diseases. The main sources of radon in homes and buildings are the ground soil and rock, ground water and building materials such as concrete and cement blocks. Radon from these sources seeps into homes and buildings and can build up to dangerous levels.

There Is No Known Safe Level Of Exposure To Radon. The EPA strongly recommends that you fix your home if your radon test shows 4 Pico curies (pCi/L) or more and even if your test shows between 2 and 4 pCi/L, consider fixing.

If your short term radon test results are borderline you should consider that the level of radon gas in a home will have high and low spikes over the period of months or seasons, and for that reason long term tests from six months to a year will give a more accurate long term average. Also the way a home is used changes from season to season i.e. heating and ventilation and will also affect the levels of radon gas. For these reasons you may want to have a long term radon test performed or conduct your own test with a long term radon kit, for a more accurate assessment before deciding to install a radon mitigation system or not. For more information on Long term radon tests see: "Testing For Radon" The Different Types Of Radon Mitigation Systemsare designed for the different types of construction of homes or office buildings. Radon mitigation deals primarily with three different building foundation types:

  1. Basement
  2. Slab on grade
  3. crawl space
Most homes or buildings with high radon have one, or a combination of these foundation types. A tree house or a house on piers wouldn't have high radon.

Homes and buildings with a basement may utilize sub-slab depressurization or suction, drain tile suction, sump hole suction or block wall suction. Crawlspace homes utilize a sub-membrane depressurization or suction.

Basement And Slab On Grade Foundations:

Active Sub-Slab Suction (also called subslab depressurization) is the most common and usually the most reliable radon reduction method. One or more suction pipes are inserted through the floor slab into the crushed rock or soil underneath, (can also be used on crawl space areas with poured concrete floors). They also may be inserted below the concrete slab from outside the house. The number and location of suction pipes that are needed depends on how easily air can move in the crushed rock or soil under the slab, and on the strength of the radon source. Often, only a single suction point is needed. A radon vent fan connected to the suction pipe(s) creates suction, drawing radon gas from below the house and releases it into the outdoor air while simultaneously creating a negative pressure (vacuum) beneath the slab. Basically it removes the radon from under the building before it ever has a chance to enter. Common fan locations include unconditioned house and garage spaces, including attics, and the exterior of the house.

Passive Sub-slab Suction is the same as active subslab suction except it relies on natural pressure differentials and air currents instead of a fan to draw radon up from below the house. Passive subslab suction is usually associated with radon-resistant features installed in newly constructed homes. Passive subslab is generally not as effective in reducing high radon levels as active subslab suction.

Drainage System Depressurization also known as drain tile suction is used on houses or buildings that have drain tiles or perforated pipe to direct water away from the foundation of the house. Suction on these tiles or pipes is often effective in reducing radon levels. This system is most effective if the drain tiles or pipe are on the inside of the footer and form a complete loop around the foundation of the building.

Sump Hole Suction is a variation of subslab and drain tile suction. Often, when a house with a basement has a sump pump to remove unwanted water, the sump can be capped so that it can continue to drain water and serve as the location for a radon suction pipe. It is important that the sump cover lid is readily removable for service of the sump pump. The sump cover needs to maintain an air-tight seal to prevent conditioned air from being pulled into the radon vent pipe. In this picture a sump cover is prepared for installation; the small diameter pipe is to discharge water from the sump pump, the larger pipe is for radon suction. There is a clear section for viewing beneath and a one way drain installed in the cover for draining a dehumidifier or furnace condensate drain line. This cover is fairly easy to remove and everything is air tight.

Block Wall Suction can be used in basements with hollow block foundation walls. This method removes radon from the hollow spaces within the basement's concrete block wall and is often used in conjunction with subslab suction.

Crawlspace Foundations/Or Basement Dirt Floor Areas :

Crawlspace Sub-Membrane Suction is an effective method to reduce radon levels in crawlspace houses. It involves covering the earth floor with a high-density plastic sheet or radon barrier. A vent pipe and fan are used to draw the radon from under the sheet and vent it to the outdoors. When properly applied is the most effective way to reduce radon levels in crawlspace houses. If regular cheap plastic sheeting is used it can become brittle in just a few years and need replacement; for this reason high quality radon barriers are recommended. See picture below, before and after the radon barrier sheeting has been installed.

Active Crawlspace Depressurization involves drawing air directly from the crawlspace using a fan. This technique generally does not work as well as sub-membrane suction and requires special attention to combustion appliance back drafting and sealing the crawlspace from other portions of the house, and may also result in increased energy costs due to loss of conditioned air from the house.

Passive Crawlspace Ventilation is when the crawlspace is passively ventilated (without the use of a fan). Crawlspace ventilation may lower indoor radon levels both by reducing the home's suction on the soil and by diluting the radon beneath the house. Passive ventilation in a crawlspace is achieved by opening vents, or installing additional vents.

Active Crawlspace Ventilation is when the crawlspace is ventilated actively (with the use of a fan). Crawlspace ventilation may lower indoor radon levels both by reducing the home's suction on the soil and by diluting the radon beneath the house. Active ventilation uses a fan to blow air through the crawlspace instead of relying on natural air circulation.

Additional Methods of Radon Reduction (that may have be used in conjunction with the above methods)

Sealing Cracks, Perimeter Drain Channels And Other Openings In The Foundation (may be done in part or in whole in conjunction to one or more of the other techniques). Sealing the cracks limits the flow of radon into your home thereby making other radon reduction techniques more effective and cost-efficient. It also reduces the loss of conditioned air. EPA does not recommend the use of sealing alone to reduce radon because, by itself, sealing has not been shown to lower radon levels significantly or consistently. It is difficult to identify and permanently seal the places where radon is entering. It is not always necessary or practical to seal all cracks or openings. Normal settling of your house opens new entry routes and reopens old ones; this is especially true of newer houses.

House Or Room Pressurization uses a fan to blow air into the basement or living area from either upstairs or outdoors. It attempts to create enough pressure at the lowest level indoors (in a basement for example) to prevent radon from entering into the house. The effectiveness of this technique is limited by house construction, climate, other appliances in the house, and occupant lifestyle. In order to maintain enough pressure to keep radon out, the doors and windows at the lowest level must not be left opened, except for normal entry and exit. This approach generally results in more outdoor air being introduced into the home, which can cause moisture intrusion and energy penalties. Consequently, this technique should only be considered after the other, more-common techniques have not sufficiently reduced radon.

Heat Recovery Ventilator (HRV), also called an air-to-air heat exchanger, can be installed to increase ventilation which will help reduce the radon levels in your home. An HRV will increase ventilation by introducing outdoor air while using the heated or cooled air being exhausted to warm or cool the incoming air. HRVs can be designed to ventilate all or part of your home, although they are more effective in reducing radon levels when used to ventilate only the basement. If properly balanced and maintained, they ensure a constant degree of ventilation throughout the year. HRVs also can improve air quality in houses that have other indoor pollutants. There will be some increase in the heating and cooling costs with an HRV, but not as great as ventilation without heat recovery. Your HRV unit will need to have the filters cleaned on a regular basis, see the owners manual for how to maintain the system.The HRV fan(s) setting should remain at the setting placed by radon contractor and keep a record of what level the fan speed was set to. HRV fan speed set to.

Important Note: Natural ventilation occurs in all houses. By opening windows, doors, and vents on the lower floors you increase the ventilation in your house. This increase in ventilation mixes outdoor air with the indoor air containing radon, and can result in reduced radon levels. However, once windows, doors and vents are closed, radon concentrations most often return to previous values within about 12 hours. Natural ventilation in any type of house should normally be regarded as only a temporary radon reduction approach because of the following disadvantages: loss of conditioned air and related discomfort, greatly increased costs of conditioning additional outside air, and security concerns.

Radon System Warning Device(s) These device(s) give you a visual and or audible warning if the Radon System has failed or failing, and also let you know the system is working properly in most instances. If these become broken or need replacement we can sell them to you at a discounted price. Give us a call or visit our online radon store.

VM2 Manometer U-tube type, active radon system visual warning device. A water column vacuum indicator. It is mounted on the system pipe in a visible location and needs to remain in clear view. Proper operation is indicated when the liquid indicator is higher on one side of the U-tube than the other. This indicates the fan motor is creating the vacuum pressure needed for proper operation. If the liquid is at equal levels on both sides of the U-tube the system is not operating properly and should be evaluated. This device should have a sticker next to it with instructions for use. Even when this indicator shows the system is working properly it does not guarantee system performance; (The EPA recommends all houses, with or without radon systems, be retested at least every 2 years).

Electronic Radon Monitor has an audible alarm that beeps if the radon level goes above 3.9 pCi/L. It also has a digital display that shows the current average radon level. This unit works similar to a carbon monoxide detector with a digital display. These are great little monitors designed for homeowner use, they can easily be reset and used to test the radon levels in different rooms or loaned out to a friend or neighbor. Coming soon: These can be purchased on this website.

Important Note:

It is the home owner’s responsibility to check these devices periodically and also the fan or other devices present. The EPA recommends all houses, with or without radon systems, be retested at least every 2 years. We sell affordable test kits designed for homeowner use or this electronic radon monitor can give a continuous radon level year after year. I have some that are several years old and they still work fine.

Radon Mitigation System Failures And Or Problems

• Appropriate action if there is an indication of failure in system is to check that the fan motor if present is operating. If it is not, check to see if the breaker is tripped. System should be evaluated to determine if the fan needs replacement.

• If there is a failed sump pump make sure the pump is working, if the water level rises above the pump to the bottom of the suction pipe the system will not work. The water level must be lowered.

• Water level rising above suction point of pipe will cause the system to fail. Check the sump pump operation if you have one. If there is a loud slurping noise during high rain fall or snow melting periods, it is probably due to water level rising from below the slab up to the suction point; wait a few days or couple of weeks and see if water level drops, or install a sump pump.

• Call the installation contractor or qualified radon contractor to evaluate and repair system.

Home Owner’s Responsibility, Living in a House with a Radon Reduction System and Maintaining Your Radon Reduction System:

Similar to a furnace or chimney, radon reduction systems need some occasional maintenance. You should look at your warning device on a regular basis to make sure the system is working correctly. Fans may last for five years or more (manufacturer warranties tend not to exceed five years) and may then need to be repaired or replaced. Replacing a fan will cost around $350 - $450 including parts and labor (2010 Price) depending on the type and location of the fan.

The EPA recommends the home owner to retest your home at least every two years to be sure radon levels remain low (below 4.0 pCi/L). We have affordable radon test kits available at discounted prices.

A home with a heat recovery ventilator (HRV) only will not have a manometer type warning device; therefore we recommend an electronic continuous radon monitor be used as a warning device we sell these devices for our clients at discounted prices).

HRV’s need to have the filter(s) and vent covers cleaned at least twice a year for proper operation.Home Owner’s Responsibility continued:

Remember, a radon fan should NEVER be turned off; it must run continuously for the system to work correctly. If the fan is not running check the circuit or call the Radon Contractor for service or fan replacement.

Heat recovery ventilator (HRV); The filter in an HRV requires periodic cleaning or if replaceable, should be changed twice a year. Follow manufacturer’s instructions for cleaning filters. Replacement filters for an HRV are easily changed and are priced between $10 and $25. Ask your contractor where filters can be purchased. Also, the vent that brings fresh air in from the outside needs to be inspected for leaves and debris and cleaned as needed. The HRV if connected to the homes heating duct system should be checked annually by a heating, ventilating, and air-conditioning professional to make sure the air flow remains properly balanced. HRV’s used for radon control should run all the time and left on the setting, high or low speed, when system was installed.

Remodeling Your Home After A Radon Mitigation System Has Been Installed

If you decide to make major structural changes to your home after you have had a radon reduction system installed (such as converting an unfinished basement area into living space), ask your radon contractor whether these changes could void any warranties. If you are planning to add a new foundation for an addition to your house, ask your radon contractor about what measures should be taken to ensure reduced radon levels throughout the home. After you remodel, retest in the lowest lived-in area to make sure the construction did not reduce the effectiveness of the radon reduction system.

If you live in the Central New York region you may contact us to give you an estimate for a radon mitigation in your home or office building. Contacting us by phone is the best way to book an appointment (Tom Francis 315-439-1103), please use our contact form for questions. We will be glad to help in any way we can.