Mold & Mildew

Mold growing in a corner of the house

  • “Why are mold, mildew and moisture in my home?”
  • “How can these problems affect the sale of my home?”
  • “Can installing a radon mitigation system possibly correct
  • these issues?”

These are some of the questions I’ve been asked by home owners during my 20 years of installing radon mitigation systems in Maryland. My answer surprises many people. I tell them that moisture in basements or crawlspaces can be greatly reduced with a properly installed radon system. This is something we in the radon industry have known about for years, and now there are studies to prove it!

An Environmental Protection Agency (EPA) study titled ‘Exploratory Study of Basement Moisture during Operation of ASD Radon Control Systems’ ( states in it’s abstract that:
“ASD (active soil depressurization) operation can produce significant moisture reductions in the basement air and walls”.
Simply put, a radon system installed to remove deadly gas from a person’s home or business provides the added benefit of significantly lowering moisture levels that, in turn, reduce the presence of mold and mildew.

The whole issue with mold or mildew is one thing – WATER! The mold cannot exist without the presence of WATER. This fact is crucial because when a home has a leak, whether it is from plumbing pipes, hot water tanks, or that pesky wall in the basement that gets damp when it rains, these leaks can lead to mold and mildew issues. Even if you have no visible leaks, a significant amount of moisture could be entering your home though the foundation walls and from under the basement slab. This can be the reason for the musty or damp earthy smell that a lot of homes get. Those homes that have been built on low lying areas or in counties with a high water table will find this issue more frequently.

So where do we go from here? The first step is to know your home. This point is the most important! Like your body will show you signs when you are starting to get sick, most homes will show signs of mold or have that musty smell.


If you are getting damp or wet basement walls most of the time the repair is simple and inexpensive to repair. Water proofing companies will tell you it will cost thousands of dollars to fix the problem and will tear up a large portion of your basement slab. The truth is if you walk around your home and really look, what is making the wall wet on the inside is usually bad gutters or downspouts, a sump ejector pipe pouring water back towards the home, or that the landscaping around the home does not slope away from the home but towards it. The easiest way to see these issues is to go outside during a heavy rainstorm and watch what the water does.

So now you have checked for and corrected any obvious leaks in your home. If the basement is still damp and has an odor, this is where the Radon System comes in. A radon system creates a vacuum under the slab that pulls out the deadly gas and exhausts it outside the home where it can do no harm. In turn, the system also pulls out large quantities of moisture in the form of vapor and exhausts it outside of the home. It’s the same effect as a when a fan dries out a carpet by blowing air across it – when air blows across water, it evaporates.

“But I have a dehumidifier in my basement to help remove excess moisture.”

EPA studies of a dehumidifier’s performance vs. an active radon system are incredible. On average, a dehumidifier can remove up to 3.5 gallons of water per day from the air in your basement. That water is either collected in a pan which you need to carry around and drain into a sink somewhere or you have a hose draining the water into the sump pit. The problem with the latter is that you are just recycling the same water through the air in your basement and never getting it out of the home and allowing the basement to dry.

A radon system can remove as much as 19 gallons of water per day from the air in your basement and deposits it outside your house.

From a cost analysis, a new, efficient dehumidifier will be about $15 per month to run; older models can be significantly higher than that.

A radon system costs around $7 per month to run.


Radon systems for Maryland homeowners that are installed by a licensed, experienced contractor offer a multitude of benefits:

-Breeches that allow radon gas into the home are sealed.
-Dangerous radon gas is expelled from the home.
-As an added benefit, excess moisture is also removed from the home.
-Removing moisture in your home reduces mold and mildew, helps to eliminate the water source for bugs and rodents, and can save you money on your electric bills in the summer by reducing the humidity load on your A/C unit.

Radon systems save lives and when you include the extra benefits of dehumidification and saving electricity; it is a no brainer to have one installed in your home now. Homes today are usually tested for radon gas as well as for the presence of mold during the inspection process of a real estate transaction. If test results show high levels of radon gas in the home, or evidence of a mold problem, the Seller almost always pays to install the mitigation system and fix the mold issue. Why not reap the benefits of the radon system yourself since it will be your hard earned money paying for it when you sell your home anyway?

There are testing kits for both radon and mold that can be found in your local home improvement store. The EPA web site has a ton of great info on all aspects of mold and even how to clean it up. It is also the source of some of the information you have just read. Remember, solving mold issues is as simple as taking away the moisture it needs to survive. This process can take a few steps to achieve, but the installation of a radon system is an integral part of the indoor air quality we all strive for ourselves and our children. Feel free to call Avanty with any questions. We may not have all the answers, but hopefully can provide other resources.