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It’s estimated that one out of three homes in Minnesota has elevated levels of radon gas.  Because of this, the Minnesota State Building Code, since 2009, now requires that all new homes in Minnesota must be built with a passive radon control system.  Of course, most existing homes do not have radon mitigation systems.  So the question I often hear is, "Should I have my home tested for radon?"  In most cases, I believe the answer is yes.

Why?  Primarily for health reasons and peace of mind, but there is a financial reason as well.  Keep in mind, a majority of home buyers are now requesting radon tests and if the results are elevated, they often ask the sellers to pay for mitigation.  So if you buy your home and do not have it tested, but the next buyer does as you are trying to sell your home, you will likely be asked to pay for the remediation if the results are high.  At that point, you'll wonder why you didn't do this earlier.

What is Radon?
Radon is a naturally occurring gas that forms in the earth.  It is colorless, odorless, tasteless and radioactive.  As it forms, it rises to the surface of the earth where it dissipates rapidly into the air.  However, when radon enters residential and other tightly enclosed structures, its concentration can rise to levels that increase cancer risks, particularly when inhabitants of homes with higher radon levels are exposed over a period of years.

The primary concern with radon is radioactive decay, or radon decay products (RDP's). Alpha radiation emits alpha particles, which damages lung tissue. This occurs when alpha energy is delivered directly to the cells' DNA. Radon Decay products have half lives of 30 minutes. This means that radon levels will be constantly fluctuating within your home as the radon decays.

The risk to the occupants is 15 times higher for smokers. Higher radon levels pose greater risks to the occupants and longer time exposed also adds greater risk.

Does Minnesota have high levels?
In general, homes in the Midwest are much more likely to have higher radon levels, due to the fact that we build most of our homes with basements, and also because Minnesota contains widespread low grade uranium and radium. About one out of three homes in Minnesota have radon levels above EPA guidelines.

Are some homes less likely to have radon?
Studies show that a home’s tightness, foundation type and soil type have no predictable effect on radon levels.

A home with a Heat Recover Ventilator (HRV) or Energy Recovery Ventilator (ERV) will have radon levels 20%-50% below comparable homes (without these systems).  HRV's are required in modern construction, but most Minnesota homes do not have this technology installed.  Most homeowners that do have these systems do not maintain them, so it is common to find excessively clogged filters inside these units during my inspections (clogged filters prevent the unit from functioning properly).  Many times, these units are not even turned on, or are not set at proper control settings.  The bottom line is that most homeowners have no idea what these devices are for.

So while HRV's are great for reducing radon levels, they are not a substitute for an actual radon mitigation system.

Should I test my home for radon?
Testing is the only way to find out how much radon is in your home. The EPA recommends that all homes be tested for radon gas, and so do we.

I just had a test performed. What do the results mean?
The EPA set a recommended action level for radon at 4.0 picoCuries/liter (pCi/L) as advice to the public on how to understand their test results. If the annual average level of radon in a home is above this action level, EPA and MDH recommend that steps be taken to lower it.

How much radon in a home is safe?
The following table shows the level of risk from radon at several different levels. These are estimates of lung cancer risk due to long-term exposure to radon. The risk estimates were adapted from the EPA's Assessment of Risks from Radon in Homes, June 2003. They show that there is no "safe" level of radon and that risk increases with higher levels of radon. The risk to smokers from radon is significantly higher than for non-smokers.

Radon (Annual
Average) Level

Additional Lung Cancer Risk
for People Who Never Smoked

20 pCi/L

36 out of 1,000

10 pCi/L

18 out of 1,000

8 pCi/L

15 out of 1,000

4 pCi/L

7 out of 1,000

2 pCi/L

4 out of 1,000

What Types of Testing are Available?

Testing for radon comes in two forms: ACTIVE and PASSIVE. Passive devices are inexpensive and can be purchased by any homeowner at most home improvement stores (approximate cost: $25). They usually come in the form of charcoal canisters, which are placed in the lowest lived-in level of the home. After the test is complete, the canister is mailed to an approved lab where it is analyzed. The results are then mailed back to you. While this method costs less than active tests, they simply are not practical for a real estate transaction. In these situations, you need an unbiased party to perform the test and you need fast results.

That is why I strongly suggest active testing. Active testing must be performed by a licensed Radon Professional, such as Suburban Home Inspections, Inc. The same procedures are followed during active testing, but the charcoal canister is replaced with an electronic monitor. Continuous Radon Monitors constantly record the radon level in the air. When the test is complete, a printed readout shows what the radon level was for each of the 48 hours. This allows you to see the fluctuations within the home, so you know what the highest and lowest readings were. The average of the 48 hours is used to determine your overall reading. The EPA suggests mitigating for all homes that average above 4.0 pCi/L.

The sample data below is from a test performed in Woodbury, MN. The test results read from left to right. One reading is recorded for each hour of the test. In this case, the EPA protocal average for the 48 hours was 6.1 pCi/L. The buyers of this home requested the sellers to have the home professionally mitigated prior to closing and the sellers agreed.  The mitigation cost was $1600.00.  A follow-up test was performed by the mitigation company after mitigation and the house average was reduced to just 0.08 pCi/L.

How is radon mitigated?

As mentioned above, Minnesota State Building Code now requires that all new homes in Minnesota must be built with a passive radon control system.  A passive radon control system is similar to a standard radon mitigation system, but there are a few key differences.

A standard radon mitigation system consists of a 3″ plastic vent pipe that starts under the slab in a basement and ends above the roof, much like a plumbing vent.  A fan is connected to this pipe, usually in the attic, so the air and gases under the slab are constantly pulled out, creating a negative pressure zone in the area under the basement slab.  This prevents most radon from entering in to the home.  If drain tile is present, the pipe can be tied in to the drain tile, as this creates a perfect way to suck air soil gases from under the entire slab.  Gaps in the slab are also sealed to help prevent radon entry.

A passive radon control system consists of the same 3″ plastic pipe, but without a fan. An electrical junction box will need to be wired in to the attic near the pipe so a fan can be easily added later, if needed. A layer of 4″ aggregate, sand, or soil gas collection mats must be installed under the basement slab, and 6 mil polyethelene laid over the aggregate before the basement slab is poured. This allows soil gases to be properly pulled from everywhere under the slab, and keeps soils gas from entering in to the home if the basement slab cracks. Any openings in the basement floor must also be sealed, such as sump baskets and bathtub drains.

Benefits to a passive system: The most obvious benefit is that you will have less radon in your home, but passive systems don’t require the use of a fan, so there is also an energy savings benefit. Another benefit to passive systems is that they will help reduce the amount of moisture in the home.

Average Costs: Most mitigation contractors will guarantee that they can reduce the radon in your home to levels below 2 pCi/L. The cost to mitigate is usually between $1,100 and $1,600. In most cases, this work can be completed in only a few hours. For a complete list of mitigation service providers in Minnesota, click the link below.

Active System - with fan installed in attic

Passive system

Mitigation Service Providers

Radon Mitigation System Photos

Here the radon pipe starts at the sump pump basin, which is sealed to maintain suction under the basement. Notice the black rubber coupling on the radon pipe. This allows for access to the sump basin.

The suction point is often placed beside a sump pump pit to allow for easy access to the sump pump. The pipe is protruding about 4" below the cement, directly above the perforated pipe leading to the sump basin.

Radon mitigation systems can be run through closets, garages or a chase to the attic. Keeping vent pipes within the house will not only look better but will make a better system. Outside system are suggested because of the ease of installation. But excess condensation, and ice will often cause early fan failures. Also attaching pipe to the outside can transfer unwanted noise to the interior. Not good if it's your bedroom!

Here is a radon fan installed in the attic. The fan produces very little noise. In most cases only a slight hum is all that can be heard within the house, even at night when all is quiet.

A manometer is placed on a visible section of pipe. It measures air pressure and flow. This assures you that the fan is functioning. This is a necessary component of a radon system since the fan is very quite. A periodic radon test will need to be performed to assure that your level stays where you want it.

When a vent pipe passes through a fire rated wall such as the wall between the house and a garage an intumescent fire barrier is needed. What for?...if a fire starts in the garage the plastic pipe will melt first and the fire barrier will plug the hole where the pipe enters the house. This slows the spread of the fire into the house.

This is the exit point of the of the pipe. The radon vents above the home and disperses in the atmosphere. A special cover is installed to protect the fan from debris and small animals.

If you are building a new home, you can have your builder incorporate radon-resistant construction techniques into your home. The techniques add, on average, less than $500.00 to the cost of the home. Many state and local building codes already require these measures to be taken in all new home construction. For detailed look at these techniques, click the following links.

Radon Resistant New Construction in MN Homes

Installation Costs & Energy Benefits