Mitigating A High Radon Level In an Existing Home


Thinking about having your home fixed to reduce the radon to a safe level?

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Many Nebraska homes have elevated indoor radon levels that should be lower. 

This page is intended to help familiarize viewers with the basic components of a radon mitigation system installed by a licensed radon mitigation business. The structural information provided here describing a radon mitigation system reflects the construction standards required of license businesses by the Nebraska Department of Health and Human Services.

As of  November 2015, there are 43 licensed radon mitigation businesses serving the public in the State of Nebraska. Each business employees at least one trained radon mitigation specialist who can design an effective system to minimize the entry of radon into your home. 

Homeowners who want to can also install a radon mitigation system in their own home. The Nebraska Radon Program recommends that homeowners who want to "fix" or "mitigate" their own home should follow the installation practices presented here.

Whenever practical, a licensed radon mitigation specialist will try to inspect your home when invited to do so. During a visit to your home, they can inspect your house and consult with you about how a system would be installed in your home. 

Designing a mitigation system often requires several discretionary decisions and the homeowners perspective is important. A properly designed mitigation system should be both effective at lowering the radon level and acceptable to the homeowner.

Radon Mitigation Systems and Moisture

Soil air drawn from beneath a basement floor is laden with moisture vapor. If your radon mitigation system is not installed properly, this moisture vapor will condense and pool inside the ventilation pipe. Moisture vapor that pools in an unheated area will freeze at low temperatures. 

A properly designed and constructed radon mitigation system will prevent radon gas and soil moisture vapor from intruding into your home.

Drilled Suction Point A radon mitigation system will collect and remove soil air from below your basement floor from either:
  1. a sump pit, if one is present, or
  2. a five-inch suction point (the size of a common CD) that will be drilled through the floor in an unfinished storage area or your utility room.  

If your home has a sump pit, then an airtight lid should be installed so radon and soil moisture vapor cannot intrude into your basement. A radon mitigation system can then be constructed to pull the soil air from within the sealed sump pit. Systems that pulled soil air from a sealed sump pit are very effective at lowering the indoor radon level.

If your home does not have a sump pit, a radon mitigation system will remove soil air from a five-inch diameter suction point (approximately the size of a CD) drilled through the basement floor. The suction point will be installed in a location that you approve of, typically in a furnace room or storage area.

Components of a Radon Mitigation System

A Radon Mitigation System consists of the following three, basic components:

  1. A suction point;
  2. The plastic ventilation pipe; and
  3. A radon fan.

1.  A suction point in the soil beneath the basement floor.  

If your home has a sump pit, a clear plastic lid can be made and installed to form a, durable, air-tight seal.   The lid can be installed with semi-permanent caulk so it is air-tight, but can be removed if necessary to permit maintenance work.

Drilling A Suction Point<-- If your home does not have a sump pit, then a five-inch diameter suction hole will be drilled through the basement floor. This suction point is typically installed in a furnace or utility room in the basement about one to two feet in from an outside wall.

Once the five-inch hole has been drilled through the basement floor, the suction point is completed by removing enough soil from beneath the floor, to fill a five-gallon bucket. This can be accomplished using a scoop, trowel, spoon, auger or even a shop vac.

To be effective, the cavity beneath the basement floor should about the size of a five-gallon bucket. This "cavity" or "void" below the hole in the basement floor is left unfilled. This "void"  serves as a "plenum" for the removal of soil air from beneath the basement floor, when the fan is activated.

Caulking a Suction Point2.  A 3 or 4 inch diameter, plastic ventilation pipe is used to convey the soil air to the point where it is exhausted.

One end of the ventilation pipe will be inserted into the hole in the basement floor and extended a few inches down into the void or "plenum". The gap between the ventilation pipe and the floor is filled with caulking to make an air-tight seal.    -->

Vent Pipe in a Closet<-- The ventilation pipe is then extended up vertically to the floor joists. Once the ventilation pipe is up into or just beneath the floor joists, it is extended horizontally to the outside of the house or into an attached garage.

Exterior Discharge SystemIf the ventilation piping takes the soil air to the outside of the house, then the radon fan will be installed on the outside of the house, just above the point where the pipe exits the side of the house. -->

If the ventilation piping is routed into the garage, then the piping will be extended vertically through the Exterior Hard Wired Fangarage and penetrate the ceiling. In such an installation, the centrifugal radon fan will be mounted on the ventilation pipe as it rises through the attic above the garage. The ventilation piping will rise vertically from the radon fan, penetrate the roof and exhaust the soil air above the roof.

<-- 3. A centrifugal radon exhaust fan is the only operating component of the system.  Radon fans are designed and manufactured to run constantly. As explained above, the radon fan will be installed either in the attic (typically above the garage) or on the outside of the house. 

Radon fans installed on the outside of the house must be hard-wired into a electric circuit. 

When the radon fan is installed in an attic, it can be powered by plugging it into an electric outlet, if the outlet is within six feet of the fan.

In most local jurisdictions the installation of a radon fan requires an electrical permit.

Indicators of a Properly Installed Radon Mitigation System

Several specific features indicate a properly designed and installed radon mitigation system:

  • Ventilation piping that does not trap soil moisture vapor condensate in a "trap" or low spot in the piping;
  • The ventilation piping should be labeled as a "Component of a Radon Reduction System";
  • The system should have a "performance indicator" to allow the homeowner to determine if the radon fan is running, if the fan is located in a remote area, such as in an attic;
  • Wherever the ventilation pipe is installed through a wall or ceiling, caulking should be used to close the penetration;
  • A radon fan mounted on the outside of a house should be hard-wired into an electric circuit.
  • Brackets or hangers should secure the ventilation pipe to the house every 72 inches horizontally and every 96 inches vertically;
  • The outlet or exhaust point from the ventilation pipe should be 10 feet above ground and 2 feet above any windows or doors within ten feet.

A.  Because of the high moisture vapor content in the soil air, the ventilation pipe of a radon mitigation system should be installed to drain any condensate on the inside of the pipe back to the suction point beneath the basement floor.

Ice On An Outlet Pipe<-- Check to make sure there aren't any low spots or "traps" in the ventilation piping that will fill with moisture vapor condense.  In areas where the ventilation pipe is installed horizontally there should A System Label Being Installedbe one inch of fall for every ten feet of horizontal run.

B. The ventilation pipe should be labeled to show that it is a component of a radon mitigation system. -->

Radon mitigation systems installed by licensed businesses will also have the company's telephone number in case service is required. 

C. A mitigation system installed by a licensed Radon Mitigation Business will also have a performance indicator. Most businesses use a plastic, U-tube (shaped) manometer to indicate that the radon fan is operating. The manometer is typically located on the ventilation pipe in the basement about four feet above the suction point. 

Caulking a Ceiling Penetration<-- D. Caulking should be installed around the vent pipe wherever it penetrates a wall or ceiling. Caulking a Wall PenetrationIf the ventilation pipe is routed up through an attached garage, the space around the pipe through the wall (into the garage) and the garage ceiling should be filled with fire-rated caulking. In most homes the garage walls and the ceiling are considered to be fire-barriers.   -->

Fan on the side of a new house<-- E. A radon fan mounted on the outside of a house should be hard-wired into an electric circuit. If a fan is mounted on the ventilation pipe in an attic, the fan can be plugged-into an outlet.  For future reference, identify the electric circuit that powers the radon fan by labeling it in the electric panel box. 

Support BracketF. Ensure that there is a bracket or hanger securing the ventilation pipe to the house every 72 inches horizontally and every 96 inches vertically. -->

G. The outlet or point where the ventilation pipe exhausts the soil air should be 10 feet above the ground and 2 feet above any windows or doors that are within ten feet.

Pipe Through Roof<-- In many case the outlet point will be above the roofline.

The outlet of a radon mitigation system through a roof should be a minimum of 18 inch high above the roof. 

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