Radon-resistant construction in new Ohio homes

Introduction
This fact sheet provides recommendations from the Ohio Department of Health (ODH) on the benefits of, and techniques for, building a radon-resistant home. Since radon in homes is not regulated in Ohio, prospective builders/buyers must decide for themselves if radon-resistant construction is a good idea for their family's new home.

These recommendations reflect unique aspects of the radon levels typical in Ohio. These levels are affected by many factors such as climate, geology and the fact that many basements are used as living spaces. These recommendations may differ slightly from the advice given by some others such as the U.S. Environmental Protection Agency (EPA).

What is radon and why is it important?
Radon is a naturally occurring gas that enters buildings from the surrounding soil. It is colorless, odorless, tasteless and radioactive. Radon is the main source of ionizing radiation to which most people are exposed. Radon is the second leading cause of lung cancer in the United States, second only to tobacco smoking. You can read more in the fact sheet Radon Testing and Use of Test Results, available by calling ODH at 1-800-523-4439.

Radon is a preventable health threat to many in Ohio. ODH estimates that one of every two (1/2) existing Ohio homes has radon levels above the EPA's recommended action level. Fortunately, most radon problems in existing homes can be fixed. However when building a new home, it is more cost effective to prevent a radon problem by building to keep radon out.

How can radon-resistant construction protect my family?
Radon-resistant construction combines common building techniques and sealing of soil gas entry points to help keep radon from entering the home and route it outdoors instead. The lower the amount of radon in your home, the lower the exposure and resulting risk to those living there.

What are the benefits of building a home radon-resistant?

It reduces your family's risk of lung cancer.
People who live in radon-resistant homes will breathe in less radon. The less radon your family is exposed to, the lower their risk of lung cancer from this form of radiation.
It can save you money.
Adding radon-resistant features to a new home will typically add between $150 - $500 to the cost of the home. Without these features, a radon problem will generally cost between $600 and $1500 to fix once the house is built. Since the chances are high that a new home in Ohio will have an elevated radon level, investing in radon-resistant features up front can save money.
System components are incorporated into the building design.
When radon-resistant features are part of the home's design, they can easily be hidden from view. This may not be possible if a radon mitigation system has to be added after the house is finished.
It may help control basement moisture in some cases.
One common source of basement moisture, the entry of water vapor through the slab, may also be reduced by radon-resistant techniques. A radon-resistant home may have less basement moisture than if it had been built without these features, thereby reducing another indoor air problem caused by excess moisture, mold.
It may add value when you sell.
Potential buyers can be reassured that a home is built radonresistant. Informed shoppers should view this as a positive feature in the Ohio housing market. For more information on radon in real estate transactions see the ODH fact sheet Radon and Real Estate in Ohio, available by calling 1-800-523-4439.

Can a radon problem be predicted prior to construction?
No. It isn't possible to predict if a home will have elevated radon levels before it is finished and occupied. Testing soil before building would be very expensive and cannot reliably forecast how much radon will enter and accumulate in the home. Besides the amount of radon produced from the soil, many other factors that are unique to a specific house's construction and operation also influence the amount of radon that is present in the home after it is built and occupied.

Geologic and home-testing data show that the potential for elevated radon in buildings is high throughout most of the entire state of Ohio. Every home in Ohio has the potentia l for elevated indoor radon levels regardless of its location.

What makes a home radon resistant?
Homes built using radon-resistant construction techniques usually rely on "passive" radon control. Socalled passive systems don't require energy or fans to move air. These systems reduce soil gas entry points and provide a route to vent the gases to the outdoors. All of the following must be present for passive radon control to occur:

Aggregate: Four inches of clean aggregate (smaller than 2 inches in diameter but larger than ¼ inch in diameter) or four inches of sand overlain with drainage material is spread under all areas that will be covered by concrete slabs and are within the home's walls. Soil-gas collection mats or drainage mats may also be used instead. This layer allows soil gases to move freely under the slab and enter an exhaust vent pipe.
Soil-gas retarder: 6 mil thick polyethylene sheeting, overlapped 12 inches at the seams and fitted closely around all pipe, wire or other penetrations, is placed over the aggregate in a basement or slab-on-grade prior to pouring the slab. The polyethylene barrier helps keep the water in the concrete so that it cures fully with minimum cracking. In crawlspaces, the polyethylene sheeting is placed directly over the soil of the crawlspace floor and sealed to the foundation walls and interior piers. This is the primary soil gas barrier in a crawl space and serves to bridge any cracks that may form after the basement slab has cured.
Vent pipe "T": A "T" fitting made of 3- or 4-inch diameter PVC ccc piping is inserted into the aggregate under the basement slab or under a crawl space's vapor barrier. The "T" allows soil gases to enter the vent pipe with little resistance.
Perforated pipe: A 3- or 4-inch diameter perforated pipe (4-inch is preferred) is laid horizontally under a crawl space's vapor barrier and connects to the PVC vent pipe "T". The perforated pipe provides numerous openings for soil gases to enter the vent assembly.
Vent pipe: The vent pipe is a 3- or 4-inch diameter PVC pipe (4-inch is preferred) that is connected to the "T" in the aggregate. If the home has a sump pit or drain-tile system, the vent pipe can instead be inserted directly into the sump pit (and a sealed sump cover added) or connected to the drain-tile loop. The vent pipe runs vertically through the building and terminates at least 12 inches above the roof's surface in a location at least 10 feet from windows or other openings and adjoining or adjacent buildings. On each floor of the home, it should be labeled "Radon Reduction System". This pipe directs the soil gases to the outdoors.
Electrical junction box: An electrical junction box is roughed in the attic near the vent pipe. It is easier and cheaper to install electrical wirin g during construction rather than adding it later. The power supply can be used if the radon control system needs to be "activated" in the future.
Roof flashing: Flashing must be installed around the vent pipe where it exits the roof to prevent leakage.

Radon Construction

Additionally, all potential soil gas entry points are sealed with caulking or expanding foam and the basement walls are waterproofed. Common entry points that require sealing include floor/wall joints, gaps around pipes, plumbing, sump pits and the tops of block walls.

Should I test for radon after the home is finished?
ODH recommends every Ohio home, even those built radon-resistant, be tested for radon. The only way to find out if the amount of radon in your home poses an unacceptable risk to your family is to test after you have moved in.

What can be done if the radon level is high?
If the home has a passive radon-control system already in place, it can be "activated" if unacceptable radon levels are present. The system is "activated" by installing an inline exhaust fan in the vent pipe, usually in the attic. The fan is wired into the electrical junction box that was roughed in. This pulls radon and other soil gases from beneath the home and exhausts them to the outdoors. A system failure-warning device should also be installed to alert you if the system malfunctions.

Is radon-resistant construction required by code?
Except for homes built in a few Ohio communities that have adopted the 2000 International Residential Code (Appendix F), builders are not required to install a full radon-resistant new construction system. Therefore, if you wish to have your home built radon-resistant, you must specifically ask your builder for such a system.

What if my builder isn't familiar with radon-resistant construction?
Homebuilders can find technical information on radon-resistant techniques in the 2000 International Residential Code (Appendix F) from the International Code Council, the EPA, the National Association of Home Builders, the National Environmental Health Association, or other organizations. Radonresistant publications available from ODH free of charge include:

U.S. EPA, Model Standards and Techniques for Control of Radon in New Residential Buildings.
U.S. EPA, Building Radon Out: A Step-By-Step Guide On How To Build Radon-Resistant Homes.
International Codes Council, Radon-Resistant Construction and Building Codes.

Where can I get more information on radon?
Copies of EPA publications and other information on radon may be obtained at:

Ohio Department of Health
Radon Program
P.O. Box 118
Columbus, OH 43216-0118
800-523-4439 or 614-644-2727

For information on licensed radon testers and mitigators call: 614-466-0061

Data and information on radon in Ohio can be found at the Ohio Radon Information System web site at: http://radon.utoledo.edu.

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Last Updated: 09/02/2002