Mitigating Radon In A Home Without Drain Tile

If your home does not have drain tile, no problem! We successfully reduced the radon levels in a 1954 Minneapolis ranch home with an initial radon level of 3.5 pCi/L. Let’s delve into the details of the process and the factors to consider when mitigating radon in a home without drain tile.

Home Conditions to Consider

Well Room

First, this home has a well room in the basement with the front step above it. In these instances, we typically need to add a suction point in this room, which we did in this case as well. We will discuss this more later.

Living Room

There is a fireplace in the living room with footings under it. The footing design, including the depth and width, can affect how radon gas moves through the soil.

Bathroom

The bathtub often has a plumbing block out underneath it, which is open to the soil.

In this instance, there was already an access panel, so we were able to simply seal the openings to the soil with spray foam.

If we had not sealed the hole, we would have lost some of our radon system’s suction. The radon system would also pull some of the conditioned air the homeowner is paying to heat and cool through that hole and exhaust it outside, resulting in a higher system operating cost.

Pressure Field Extension Testing

We use diagnostic pressure field extension testing in every home to determine where to place suction points, how many suction points we need, how much suction we need to apply to the soil, what size pipe we need to use, and which radon fan to use.

The key to lowering radon levels is to create negative suction or vacuum under the entire house. This diagnostic testing process allows us to test and measure how far the system reaches and if we need additional suction points.

Test Holes

We start with test holes. This home has about eight test holes, which allowed us to measure the suction created by the radon fan.

In this case, we just pulled back a corner of the carpet, drilled a half-inch hole through the slab, and then put a rubber cork in the hole attached to a tube that goes back to our micromanometers.

When we’re done, we’ll fill the holes and stretch the carpet back in place, and you will never know it was there.

Micromanometers

All the tubing from our test holes returns to our micromanometers, where we measure the suction the radon system creates.

Once our suction points are in place, all our numbers should be negative. If we shut off the radon fan, these numbers will all go positive, which means the house is sucking radon into the home instead.

Pitot Tube

Once we determine the location of our first suction point, we apply suction using a pitot tube. This tells us if we’re reaching the other test holes and need additional suction points.

This works by sealing it into the suction hole before installing the pipe. Then, we use a shop vacuum hooked up to the other end. The pitot tube has a valve, so we can simulate a radon fan.

In a perfect world, if we could have everything sealed and engineer the ideal radon system, we would shoot for -3 pascals in the furthest, weakest test hole under max depressurization conditions. Max depressurization is turning on the dryer, the bath fans, the range hood, and all the stuff in the house that is fighting against the radon system and exhausting air.

Suction Point Locations

This home does not have drain tile. It also has clay soil below the slab, and it is challenging to move air through clay soil. So we want to try to find some settling below the slab so we can use that to move air more efficiently so the fan doesn’t have to work so hard.

We removed about 25 gallons of clay soil to help move air beneath the slab. Some of it was even moist clay, as seen in the image above, which can become quite compact.

First Suction Point: Utility Room

The first suction point is in the utility room. We chose this location because there is a closet above it. Our pipe came up through the upstairs closet and exhausts out through the roof on the back of the house behind the chimney. The radon fan is directly above the closet in the house’s attic.

This location also has some plumbing for the kitchen and a floor drain that runs through it. So, we used a metal detector to trace where the cast iron plumbing ran. We could then enter the loose soil created when they laid the plumbing there. They typically dig a trench, put the plumbing in, and kick the soil back in so it’s not as compact, allowing us to move air more easily there.

We cored a 5-inch hole through the floor and removed about 20 gallons of clay for this suction pit.

Second Suction Point: Laundry Room

The pressure field extension testing helped us determine we needed an additional suction point in the laundry room.

Third Suction Point: Well Room

After adding the second suction point, we found we still weren’t reaching the well room, so we added a third suction point there. We located some settling in the well room where the old well pipe used to go through.

We also installed a valve on the pipe to control the airflow. In this case, we needed all the airflow we could get, so it was all the way open. We are only moving 17 cfm.

We used a tee in the laundry room to tie all three suction points together. We also ensured we followed code by securing the pipe every 6 feet horizontally.

System Monitors

We outfit all our systems with system monitors.

First, we have an audible alarm at the top of the pipe, which will let you know if the radon fan fails.

Then, we have our visual manometer, also referred to as a U-tube. This measures the suction of the radon fan. When the radon fan is working, the fluid levels will not be level. If it’s not working, they will be equal at zero.

Operating Costs

The 107-watt fan we used for this system will cost $116 a year to operate. About $107 of that will go to power the fan. The other $9 is our estimated conditioned air loss.

Results

When we arrived, the radon level was about 5.0 pCi/L. We started the radon system, and within a couple of hours, we saw it steadily drop. The final post-mitigation average was 0.7 pCi/L.

Wrap Up

To wrap up, we conducted a backdraft test on the natural draft water heater to ensure it didn’t have carbon monoxide issues.

The electrician came to add an outlet and a light in the attic. We also made sure that the electrician labeled the breaker that the radon system is on.

If you are looking for radon system service or installation and are in the Minneapolis, MN, area, contact us here.