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Radon Mitigation Systems Temporary Clogging Due to Ice Jams

What causes radon vent pipes to freeze?

The issue of radon mitigation systems temporarily clogging due to ice forming on the vent pipe of the radon fan is common in freezing weather climates.  The very nature of a radon system pulling damp air from under structural concrete slabs and crawlspace liners creates this issue.

To explain further, radon travels up into a home from deep in the soil.  Radon mitigation systems operate continuously actively drawing radon gas from under concrete slabs, sump pit basins, and crawlspace liners.  Moisture vapor and other soil gases also travel up through a radon system since they both are present in the soil.  There are many benefits to radon system pulling the moisture vapor and soil gases out from under a building, like lower relative humidity, reduced odors, and cleaner air.  The only downside of a radon system drawing out moisture vapor is the potential for ice jabs in cold winter months.Radon Mitigation Systems Temporary Clogging Due to Ice Jams - Image 1

The amount of moisture being extracted from under a home can be quite significant.  The moisture travels up and exits out into the atmosphere through the vent pipe on the radon system.  Directly above the radon fan it is typical to have condensation form and actually drip back down through the fan into the pipe below the radon fan.  The fan continuously transfers that liquid condensation back into moisture vapor and sends the moisture back up the vent pipe.  However, the condensation inside the vent pipe cannot be avoided, regardless of the weather.  Condensation drip is a larger problem if the radon contractor used gutter downspout for the vent pipe, versus 40-gauge PVC pipe, since most downspout is not insulated. 

The condensation inside the pipe can then change into ice if the temperature is below freezing consistently.  It’s quite common in northern United State and Canada.  It’s also more common on long vent pipe runs (over 10 feet) or with metal downspout vent pipes, as stated earlier.

What can be done to prevent freezing radon system vent pipes?

The first recommendation we have for preventing vent pipe ice jams is removing, or not installing, varmint guards, vent covers, critter guards, or exhaust caps.  These are natural places for ice to start forming from the condensation collecting on these products.  We recommend letting the air flow freely up out of the vent pipe.  Since air is flowing out of the systems varmints and debris have a hard time entering the system, although certainly possible.  The benefits of a system not freezing outweigh the downsides for most people. 

Do not use uninsulated gutter downspout for your vent pipe.  Although some people feel that gutter downspout looks aesthetically more appealing than PVC pipe, it’s not a promising idea to use it because the seams don’t seal well, and the lack of insulation causes more condensation to form inside the pipe.

Keep the vent pipe as short as possible. The longer the vent pipe runs the more condensation is held inside the vent pipe. Condensation is not able to clear completely out of the end of the pipe.   Keeping the vent pipe short can be a challenge since the US Radon Code (ASTM 2121 Guidelines) requires vent pipe to vent above the lowest gutter line of the house.  Canada recognizes their cold climate could cause ice jams, so they specifically state that vent pipes are not required.  In fact, Canada’s radon mitigation system guidelines now do not have the same requirement as the United States, because of this very issue.   Unfortunately, that is not accepted practice in the United States and contractors could be fined for installing radon systems without professionally installed pipes.

Drain the condensation below the fan.  One option for removing some of the condensation and lowering the risk of freezing is to drain the condensation below the fan for exterior mounted systems.  A certified radon expert can install a tee pipe connection, instead of a 90-degree connector below the radon fan.  One side of the tee fitting will support the fan, while the other end of the tee is capped and has a small ¼” hole in it to drain the condensation aimed directly towards the ground below the fan.  The downside to this approach is the creation of a puddle of water below the fan in the warmer months and a large ice sickle below the fan in the colder months.

Heating the pipe with an electrical warming coil. Another option to reduce the chances of ice jams is to wrap the vent pipe with an electrical warming coil and plug that into an exterior outlet.  This can work in some situations if the heat is strong enough.  The downside is aesthetics and electricity consumption.

Wait for it to thaw.  Most people simply wait for warmer weather and let the system thaw out on its own.  Knowing that the dangers of radon exposure are accumulated over long periods of time, many people are comfortable with a couple months of a little higher level in their home.  This option is obviously up to each person’s comfort level with knowingly exposing themselves to higher radon levels.

Is the system still working a little, even though it’s clogged?  The answer to this question can be yes, a little.  Upon doing performance testing on systems that are partially, or completely clogged, we have found that radon systems still make a slight draw on the slabs and crawlspaces when they are clogged. This may vary significantly, however, and the performance is certainly not ideal.  Systems can operate differently, so it’s a good idea to do your own radon testing to determine your levels. 

Keep in mind, radon mitigation contractors are typically not responsible for natural weather-related issues impacting your radon system.  The performance of a radon system is measured over the average radon level per year, which is an average for a 12-month period. 

Are there other approaches to keeping radon levels low in these cold months, besides a radon mitigation system?  Yes.  There are two approaches to consider: 1) Increase ventilation and 2) Filtration.   

Increased ventilation is a strategy of bringing more fresh, clean air into a home or building.  These systems are referred to as air exchangers (i.e. Heat Recovery Ventilator or Energy Recovery Ventilator).  These mechanical devices draw in air from outside, condition it, and circulate it into your home.  The systems replace some of your inside air.  They can be balanced for efficiency.  Studies have shown an average of 50% reduction of radon gas and other indoor air pollutants from homes using these systems.

The filtration approach is easy and economical.  First off, let me qualify that you cannot filter Radon.  Radon is a noble gas.  However, you can filter the Radon Decay Particles that are the biproducts of radon.  Radon Decay Products are what cause lung cancer by being inhaled and attaching to the soft tissue of the lungs.

Filtering Radon Decay Product (RDP) has been proven extraordinarily successful. A high-end air filter is recommended for this approach, like the Breathe EZ Air Cleaner, or another MERV 13+ filter. Learn more about this product by going to www.breatheezair.com.  The Breathe EZ Air Cleaner has been tested and proven to filter RDP up to 98%.  It can be installed by a professional without any adjustments to the duct work of your home's HVAC system.

The first key to filtering Radon Decay Product is installing a MERV 13, or better, filter in your air handler (i.e. furnace).  The second key is circulating air consistently in the home.  If air is not circulating, then it is not being filtered.  Thus, the Radon Decay Product will be present.  Other benefits of this type of filter are reduced dust, allergens, chemicals, viruses, and odors in your air. Again, keep in mind your Radon levels will not be impacted, just your Radon Decay Product levels.  Filtering and removal of Radon Decay Product will reduce your risks of radon induced lung cancer.

Who should I contact for help?

Contact a radon professional in your local market for professional advice on your system.  Hopefully, this will be the company that installed your system or contact a member of the National Radon Defense network (www.nationalradondefense.com)  of certified and trained professionals.  They will discuss with you an approach that will help you and your family during this period of cold weather.


Article written by Curt Drew, President, and Founder of National Radon Defense