WHAT IS OPTIMAL MITIGATION?
What do we mean when we talk about optimal mitigation? Optimal mitigation refers to a mitigation system that reduces radon levels as much as possible with the lowest energy consumption possible. We strive to create effective and efficient systems, which includes asking ourselves, “How can we make it better?”
To achieve optimal mitigation, it’s necessary to perform pressure field extension (PFE) testing, which measures the amount of suction a system creates under every area of the home. With PFE, we can engineer a system that creates the suction necessary to reduce radon levels without consuming excessive energy.
To demonstrate how we strive for optimal mitigation, let’s look at the house we mitigated as part of our training course in 2022. It was a 1975 house with a full, unfinished basement and attached garage. Before mitigation, the owner did two separate charcoal tests with results of 9.9 pCi/L and 11.1 pCi/L.
DESIGNING THE SYSTEM
We installed a system that ran up from the basement through the garage attic. With one suction point, we struggled to reach the far corner of the basement. We could lower radon levels with a high-powered fan, but that would mean a greater energy penalty, and bigger fans create louder systems.
To improve our suction, we started with sealing. First, we sealed the floor-to-wall joint and any gaps or cracks that we could find. Sealing improves suction, which allows us to use a smaller fan, and lowers the amount of conditioned air drawn from the home.
We added a second suction point near the plumbing to take advantage of the settling. However, even with two suction points, we would still need a high-powered fan to reach the back corner of the home.
We looked for more gaps to seal. One of the visiting mitigators, Charlie Gutridge, noticed a gap under the furnace. Using a smoke pen, we could confirm that the mitigation system was drawing air under the furnace. We cut open the bottom and found a hole.
In Minnesota, when they build houses in the winter, they hang the furnace from the floor joist and then pour the concrete. In this instance, the concrete didn’t reach all the way under the furnace, creating a large hole that reduced our PFE. Once we sealed it, we went from about 4.1 inches of static pressure down to 3 inches. That’s the difference between using an Eagle Extreme and an Eagle radon fan.
However, we knew that we could still improve efficiency. We added a third suction point closer to our weakest corner, next to the sewer cleanout. Our suction in the far corner improved significantly. We used a valve to adjust how much air we pulled from this third suction point. We only needed to pull 1 CFM to reach our target of about -4.5 Pa in that weakest corner.
ADDITIONAL RADON ENTRY POINT
Having reached full PFE, we set up EcoTrackers and left them out overnight to see how well the system reduced radon levels. To our surprise, when we came back the next morning, our EcoTrackers still read about 1.2 pCi/L. Because there is no known safe level of radon, we wanted to see if we could reduce levels even further.
We had pressure field extension everywhere, so we looked for other penetrations but didn’t find anything. So next, we thought about adjacent slabs — specifically the slab for the attached garage and the slab for the front step.
Near the slab for the front step, we found spiderwebs. Spiders build webs where there’s airflow, so we put an EcoTracker in the web’s place. The readings began to climb. Over about thirty minutes, it reached 3 pCi/L. We cored a hole through the wall and stuck an EcoTracker inside. The monitor read over 6 pCi/L. We had found our culprit.
We dug a suction pit under the front step, ran a 2-inch line over to it, and cut it into our system.
This fourth suction point brought our EcoTracker readings down to about 0.6 pCi/L. Our final Air Chek result was 1.1 pCi/L. The system used a FanTech Rn1 pulling 15.5 watts at about 22 CFM, with about 2 CFM coming from the house. The system operating cost was $20 a year.
While one suction point with a high-powered fan may have reduced radon levels, we likely would not have seen levels as low and would have had a much higher operating cost. So while these additional steps are more work up front, they pay off over the life of your system.
If you want a contractor who takes the time to engineer a system for optimal mitigation, fill out our estimate request form or call us at 612-474-1004.
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