Have you ever wondered how we perform radon mitigation in a rambler, sometimes referred to as a ranch home? Let’s take a look at our installation process for this 1978 rambler with a full basement and an initial radon level of 15.7 pCi/L. Or check out the video.
PRESSURE FIELD EXTENSION
The key to engineering an effective radon mitigation system is creating a vacuum under the entire house. To measure the amount of suction we’re creating under every area of the home, we perform pressure field extension testing. We started by drilling diagnostic test holes—half-inch holes through the concrete floor—in different areas of the home. In this house, we drilled 8 test holes. Then, we took rubber stoppers hooked up to tubing and sealed one in each test hole. The tubing ran back to micromanometers, which measured the negative pressure, or suction, in each test hole.
RADON MITIGATION: FIRST SUCTION POINT
Our diagnostic tests helped us determine where to place our first suction point to achieve the best pressure field extension. This house didn’t have drain tile, so we chose a spot next to a footing and plumbing because those areas had looser soil, and the system will be able to pull air through loose soil better than compacted soil.
We dug a 10-gallon suction point. There were 4 inches of sand and gravel on top of clay. Once we finished, we sealed a pitot tube in the floor and attached a shop vac. The pitot tube allowed us to measure and adjust the amount of air that we were moving to mimic the suction that a radon fan would create.
We checked our micromanometers to see where we were creating negative pressure. We realized that we weren’t reaching the bedrooms on the far side of the house or the living room in the front corner of the house. So we needed to add a second suction point.
RADON MITIGATION: SECOND SUCTION POINT AND SEALING
Again, we wanted to be next to plumbing. To reach the bedrooms, we created a 15-gallon suction point next to a bathroom. When working next to showers, we look for a plumbing block out, which is a hole that is open to the soil. We want to seal gaps and cracks open to the soil wherever we can to create an effective and efficient system. You can learn more about the importance of sealing here. For example, in this house, there was a fiberglass shower pan that sat on the ground. We couldn’t seal that hole, so we foamed the shower pan to the floor. A foam gun with a long nozzle works well to reach areas like these. There was also a big air leak around the toilet, so we sealed it to the floor with silicone.
We added a valve, which allowed us to control how much air the fan could pull from this area.
This second suction point helped us reach the bedrooms, but we still weren’t creating adequate suction by the TV in the living room.
RADON MITIGATION: THIRD SUCTION POINT – STITCHING
To reach that final area of the house, we created a third suction point in the mechanical room next to a load-bearing wall that separated the mechanical room and living room. There wasn’t a beam running across the house, so we knew that a center footing ran from the garage all the way to the bedrooms. It was challenging to get airflow on the other side of the footing, especially since it sat on clay.
One option was to run a pipe through the wall and create a suction point in the living room. However, we don’t love the way that looks, and we don’t want to do anything in our customers’ homes that we wouldn’t do in our own.
Instead, we decided to stitch under the wall. From our suction point in the mechanical room, we auger-ed under the footing. In the living room, we pulled back the carpet and cored a hole through the floor. We dug a suction point so we could reach the front corner of the house. Then, we auger-ed under the footing to tie into the suction point on the other side of the wall. We placed a Styrofoam plug in the hole and re-poured the concrete. After putting the carpet back, our work was undetectable.
With our third suction point complete, we were finally satisfied with our pressure field extension.
RADON MITIGATION: VENT PIPE AND FAN
From the mechanical room, the vent pipe ran out into the garage. As required by code, we placed a firestop collar around the pipe where it went through the shared wall between the house and garage. Firestop collars are meant to protect the house in the event of a garage fire.
We also put insulation on our pipe. We acknowledge it’s not the most attractive, but it protects the system from freeze-up and stops condensation from forming on the pipe and dripping off onto the sheetrock.
We also installed the fan in the garage.
We used an EC radon fan with a potentiometer, which allowed us to dial the fan to the desired setting. Adjusting the fan’s power helps us save on operating costs. In this system, we didn’t need the fan set at 100%. Instead, we set it to about 60%.
From there, the pipe exhausted out the roof. We placed a critter guard cap on top, preventing debris such as acorns from falling into the pipe. We also painted the pipe to match the shingles. The darker color looks nicer and helps the pipe stay a little warmer, making it less likely to freeze. We also use 4-inch pipe when we’re outside to help prevent freeze-ups.
Finally, it was time to dial everything in. In the winter, we want to get 3 pascals of negative pressure in our furthest, weakest test hole under max depressurization. Between the adjustable fan and the valve on our second suction point, we could adjust everything so that we had an extremely efficient system. For example, if we had left our fan cranked to 10 moving 80 cfm, it would have cost about $389 a year to operate. Instead, we could get our operating costs down to $75 a year for savings of $314 a year. In 10 years, this customer will save over $3,000.
We added an MDH system tag, audible alarm, and a visual manometer as required by code.
To wrap up, we re-stretched the carpet and did a backdraft test on the natural draft water heater.
Finally, we conducted a post-mitigation test. We started with a radon level of 15.7 pCi/L. Our post-mitigation radon result was 1 pCi/L.
If you’re interested in lowering your radon levels as much as possible, contact us to set up a free estimate.
If you’d like guidance designing a mitigation system, see if our consulting services are right for you.
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