How radon enters your house
Radon is a naturally occurring radioactive gas produced by the breakdown of uranium in soil, rock, and water. Air pressure inside your home is usually lower than pressure in the soil around your home’s foundation. Because of this difference in pressure, your house acts like a vacuum, drawing radon in through foundation cracks and other openings. Radon may also be present in well water and can be released into the air in your home when water is used for showering and other household uses. In most cases, radon entering the home through water is a small risk compared with radon entering your home from the soil. In a small number of homes, the building materials (e.g., granite and certain concrete products) can give off radon, although building materials rarely cause radon problems by themselves. In the United States, radon gas in soils is the principal source of elevated radon levels in homes.
Radon is a cancer-causing, radioactive gas
Radon is estimated to cause many thousands of lung cancer deaths each year. In fact, the Surgeon General has warned that radon is the second leading cause of lung cancer in the United States. Only smoking causes more lung cancer deaths. If you smoke and your home has high radon levels, your risk of lung cancer is especially high.
What do your radon test results mean?
Any radon exposure has some risk of causing lung cancer. The lower the radon level in your home, the lower your family’s risk of lung cancer. The amount of radon in the air is measured in "picoCuries of radon per liter of air," or "pCi/L." Sometimes test results are expressed in Working Levels, "WL," rather than picoCuries per liter of air. A level of 0.02 WL is usually equal to about 4 pCi/L in a typical home.
The U.S. Congress has set a long-term goal that indoor radon levels be no more than outdoor levels; about 0.4 pCi/L of radon is normally found in the outside air. EPA recommends fixing your home if the results one long-term test or the average of two short-term tests show radon levels of 4 pCi/L (or 0.02 WL) or higher. With today’s technology, radon levels in most homes can be reduced to 2 pCi/L or below. You may also want to consider fixing if the level is between 2 and 4 pCi/L.
A short-term test remains in your home for 2 days to 90 days, whereas a long-term test remains in your home for more than 90 days. All radon tests should be taken for a minimum of 48 hours. A short-term test will yield faster results, but a long-term test will give a better understanding of your home’s year-round average radon level.
The EPA recommends two categories of radon testing. One category is for concerned homeowners or occupants whose house is not for sale. The second category is for real estate transactions.
Why hire a contractor?
EPA recommends that you have a qualified radon mitigation contractor fix your home because lowering high radon levels requires specific technical knowledge and special skills. Without the proper equipment or technical knowledge, you could actually increase your radon level or create other potential hazards and additional costs. However, if you decide to do the work yourself, get information on appropriate training courses and copies of EPA’s technical guidance documents from your state radon office.
Will any contractor do?
EPA recommends that you use a state certified and/or qualified radon mitigation contractor trained to fix radon problems. You can determine a service provider’s qualifications to perform radon measurements or to mitigate your home in several ways. First, check with your state radon office. Many states require radon professionals to be licensed, certified, or registered, and to install radon mitigation systems that meet state requirements. Most states can provide you with a list of knowledgeable radon service providers doing business in the state. In states that don’t regulate radon services, ask the contractor if they hold a professional proficiency or certification credential, and if they follow industry consensus standards such as the American Society for Testing and Materials (ASTM) Standard Practice for Installing Radon Mitigation Systems in Existing Low-Rise Residential Buildings, E2121 (March 2001), or the U.S. EPA’s Radon Mitigation Standards (EPA 402-R-93-078, revised April 1994). You can contact private proficiency programs for lists of privately-certified professionals in your area. Such programs usually provide members with a photo-ID, which indicates their qualification(s) and the ID-card’s expiration date.
How to select a contractor – get estimates
Choose a contractor to fix a radon problem just as you would choose someone to do other home repairs. It is wise to get more than one estimate, to ask for references, and to contact some of those references to ask if they are satisfied with the contractors’ work. Also, ask your state radon office or your county/state consumer protection office for information about the contractors.
Use this check-list when evaluating and comparing contractors and ask the following questions:
- Will the contractor provide references or photographs, as well as test results of ‘before’ and ‘after’ radon levels of past radon reduction work?
- Can the contractor explain what the work will involve, how long it will take to complete, and exactly how the radon reduction system will work?
- Does the contractor charge a fee for any diagnostic tests? Although many contractors give free estimates, they may charge for diagnostic tests. These tests help determine what type of radon reduction system should be used and in some cases are necessary, especially if the contractor is unfamiliar with the type of house structure or the anticipated degree of difficulty.
- Did the contractor inspect your home’s structure before giving you an estimate?
- Did the contractor review the quality of your radon measurement results and determine if appropriate testing procedures were followed?
Compare the contractors’ proposed costs and consider what you will get for your money, taking into account: (1) a less expensive system may cost more to operate and maintain; (2) a less expensive system may have less aesthetic appeal; (3) a more expensive system may be best for your house; and, (4) the quality of the building material will affect how long the system lasts.
Do the contractors’ proposals and estimates include:
- Proof of state certification and/or professional proficiency or certification credentials?
- Proof of liability insurance and being bonded, and having all necessary licenses to satisfy local requirements?
- Diagnostic testing prior to design and installation of a radon reduction system?
- Installation of a warning device to caution you if the radon reduction system is not working correctly?
- Testing after installation to make sure the radon reduction system works well?
- A guarantee to reduce radon levels to 4 pCi/L or below, and if so, for how long?
Ask the contractor to prepare a contract before any work starts. Carefully read the contract before you sign it. Make sure everything in the contract matches the original proposal. The contract should describe exactly what work will be done prior to and during the installation of the system, what the system consists of, and how the system will operate. Many contractors provide a guarantee that they will adjust or modify the system to reach a negotiated radon level. Carefully read the conditions of the contract describing the guarantee. Carefully consider optional additions to your contract which may add to the initial cost of the system, but may be worth the extra expense. Typical options might include an extended warranty, a service plan, and/or improved aesthetics.
Important information that should appear in the contract includes:
- The total cost of the job, including all taxes and permit fees; how much, if any, is required for a deposit; and when payment is due in full.
- The time needed to complete the work.
- An agreement by the contractor to obtain necessary permits and follow required building codes.
- A statement that the contractor carries liability insurance and is bonded and insured to protect you in case of injury to persons, or damage to property, while the work is done.
- A guarantee that the contractor will be responsible for damage and clean-up after the job.
- Details of any guarantee to reduce radon below a negotiated level.
- Details of warranties or other optional features associated with the hardware components of the mitigation system.
- A declaration stating whether any warranties or guarantees are transferable if you sell your home.
- A description of what the contractor expects the homeowner to do (e.g., make the work area accessible) before work begins.
Checking your contractor’s work
Below is a list of basic installation requirements that your contractor should meet when installing a radon reduction system in your home. It is important to verify with your contractor that the radon mitigation standards are properly met to ensure that your radon reduction system will be effective. You can also check with your state radon office to see if there are state requirements that your contractor must meet.
- Radon reduction systems must be clearly labeled. This will avoid accidental changes to the system which could disrupt its function.
- The exhaust pipe(s) of soil suction systems must vent above the surface of the roof and 10 feet or more above the ground, and at least 10 feet away from windows, doors, or other openings that could allow the radon to reenter the house, if the exhaust pipe(s) do not vent at least 2 feet above these openings.
- The exhaust fan must not be located in or below a livable area. For instance, it should be in an unoccupied attic of the house or outside – not in a basement!
- If installing an exhaust fan outside, the contractor must install a fan that meets local building codes for exterior use.
- Electrical connections of all active radon reduction systems must be installed according to local electrical codes.
- A warning device must be installed to alert you if an active system stops working properly. Examples of system failure warning devices are: a liquid gauge, a sound alarm, a light indicator, and a dial (needle display) gauge. The warning device must be placed where it can be seen or heard easily. Your contractor should check that the warning device works. Later on, if your monitor shows that the system is not working properly, call a contractor to have it checked.
- A post-mitigation radon test should be done within 30 days of system installation, but no sooner than 24 hours after your system is in operation with the fan on, if it has one. The contractor may perform a post-mitigation test to check his work and the initial effectiveness of the system; however, it is recommended that you also get an independent follow-up radon measurement. Having an independent tester perform the test, or conducting the measurement yourself, will eliminate any potential conflict of interest. To test the system’s effectiveness, a 2-7 day measurement is recommended. Test conditions: windows and doors must be closed 12 hours before and during the test, except for normal entry/exit.
- Make sure your contractor completely explains your radon reduction system, demonstrates how it operates, and explains how to maintain it. Ask for written operating and maintenance instructions and copies of any warranties.
What to look for in a radon reduction system
In selecting a radon reduction method for your home, you and your contractor should consider several things, including: how high your initial radon level is, the costs of installation and system operation, your house size and your foundation type.
Installation and operating costs
The cost of a contractor fixing a home generally ranges from $800 to $2,500, depending on the characteristics of the house and choice of radon reduction methods. The average cost of a radon reduction system is about $1,200.
Most types of radon reduction systems cause some loss of heated or air conditioned air, which could increase your utility bills. How much your utility bills will increase will depend on the climate you live in, what kind of reduction system you select, and how your house is built. Systems that use fans are more effective in reducing radon levels; however, they will slightly increase your electric bill. The "Installation and Operating Cost Table" lists the installation and average operating costs for different radon reduction systems and describes the best use of each method.
Radon reduction techniques
There are several methods that a contractor can use to lower radon levels in your home. Some techniques prevent radon from entering your home while others reduce radon levels after it has entered. EPA generally recommends methods which prevent the entry of radon. Soil suction, for example, prevents radon from entering your home by drawing the radon from below the house and venting it through a pipe, or pipes, to the air above the house where it is quickly diluted.
Any information that you may have about the construction of your house could help your contractor choose the best system. Your contractor will perform a visual inspection of your house and design a system that considers specific features of your house. If this inspection fails to provide enough information, the contractor will need to perform diagnostic tests during the initial phase of the installation to help develop the best radon reduction system for your home. For instance, your contractor can use chemical smoke to find the source and direction of air movement. A contractor can learn air flow sources and directions by watching a small amount of smoke that he or she shot into holes, drains, sumps, or along cracks. The sources of air flow show possible radon routes. A contractor may have concerns about backdrafting of combustion appliances when considering radon mitigation options, and may recommend that the homeowner have the appliance(s) checked by a qualified inspector.
Another type of diagnostic test is a "soil communication test." This test uses a vacuum cleaner and chemical smoke to determine how easily air can move from one point to another under the foundation. By inserting a vacuum cleaner hose in one small hole and using chemical smoke in a second small hole, a contractor can see if the smoke is pulled down into the second hole by the force of the vacuum cleaner’s suction. Watching the smoke during a soil communication test helps a contractor decide if certain radon reduction systems would work well in your house.
Whether diagnostic tests are needed is decided by details specific to your house, such as the foundation design, what kind of material is under your house, and by the contractor’s experience with similar houses and similar radon test results.
House foundation types
Your house type will affect the kind of radon reduction system that will work best. Houses are generally categorized according to their foundation design. For example: basement, slab-on-grade (concrete poured at ground level), or crawlspace (a shallow unfinished space under the first floor). Some houses have more than one foundation design feature. For instance, it is common to have a basement under part of the house and to have a slab-on-grade or crawlspace under the rest of the house. In these situations a combination of radon reduction techniques may be needed to reduce radon levels to below 4 pCi/L.
Radon reduction systems can be grouped by house foundation design. Find your type of foundation design above and read about which radon reduction systems may be best for your house.
Basement and slab-on-grade houses
In houses that have a basement or a slab-on-grade foundation, radon is usually reduced by one of four types of soil suction: subslab suction, drain tile suction, sump hole suction, or block wall suction.
Active Subslab 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. 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 contractor usually gets this information from visual inspection, from diagnostic tests, and/or from experience. A radon vent fan connected to the suction pipe(s) draws the radon gas from below the house and releases it into the outdoor air while simultaneously creating a negative pressure (vacuum) beneath the slab. Common fan locations include unconditioned house and garage spaces, including attics, and the exterior of the house.
Passive subslab 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.
Some houses 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.
One variation of subslab and drain tile suction is sump hole 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.
Block wall suction can be used in basement houses with hollow block foundation walls. This method removes radon and depressurizes the block wall, similar to subslab suction. This method is often used in combination with subslab suction.
An effective method to reduce radon levels in crawlspace houses involves covering the earth floor with a high-density plastic sheet. A vent pipe and fan are used to draw the radon from under the sheet and vent it to the outdoors. This form of soil suction is called submembrane suction, and when properly applied is the most effective way to reduce radon levels in crawlspace houses. Another less-favorable option is active crawlspace depressurization which involves drawing air directly from the crawlspace using a fan. This technique generally does not work as well as submembrane suction and requires special attention to combustion appliance backdraftiing 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.
In some cases, radon levels can be lowered by ventilating the crawlspace passively (without the use of a fan) or 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. Passive ventilation in a crawlspace is achieved by opening vents, or installing additional vents. Active ventilation uses a fan to blow air through the crawlspace instead of relying on natural air circulation. In colder climates, for either passive or active crawlspace ventilation, water pipes, sewer lines and appliances in the crawlspace may need to be insulated against the cold. These ventilation options could result in increased energy costs for the house.
Other types of radon reduction methods
Other radon reduction techniques that can be used in any type of house include: sealing, house/room pressurization, heat recovery ventilation, and natural ventilation.
Sealing cracks and other openings in the foundation is a basic part of most approaches to radon reduction. 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. Normal settling of your house opens new entry routes and reopens old ones.
House/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.
A 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 could be significant increase in the heating and cooling costs with an HRV, but not as great as ventilation without heat recovery (see the "Installation and Operating Cost Table").
Some 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.
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 $200 – $350 including parts and labor. It is a good idea to retest your home at least every two years to be sure radon levels remain low.
Remember, the fan should NEVER be turned off; it must run continuously for the system to work correctly.
The filter in an HRV requires periodic cleaning and should be changed twice a year. 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. The ventilator should be checked annually by a heating, ventilating, and air-conditioning professional to make sure the air flow remains properly balanced. HRVs used for radon control should run all the time.
For information on radon in water, testing and treatment, and existing or planned radon in drinking water standards, or for general help, call EPA’s Drinking Water Hotline at (800) 426-4791 or visit www.epa.gov/safewater/radon.html. If your water comes from a private well, you can also contact your state radon office.