There are many factors that go into radon fan selection: soil type, foundation size/type, radon level, PVC size, climate, humidity, etc. Soil type is an important factor to consider; however it is far from the only factor. Here is a general overview of soil types and fans that can often be considered.
Foundation type dictates system type
In this article, we’ll consider slab foundations. You may have a crawlspace with gravel or dirt floor. You may have a sump system. You may have multiple foundations. If that is the case, this article may not be of help to you. Always consider the easiest airflow path. If you have an existing de-watering sump or French drain system, you’re in luck, a French connection and a bit of digging could get you in and out quickly—even with clay soils. If you have a radon ready passive system that was done correctly, then even with tight clay soils you may find you’re able to use other radon fan types. There are many links above and throughout this article that can take you to other articles that may be better suited to your problems.
Suction pit
Clay soils are what we call “tight soils”. They allow the least amount of water and airflow movement, which means they are the most restrictive. In radon mitigation, restrictions mean you’ll see higher suction. Think of tight soils like a thick milkshake: you really have to suck on your straw to get to the good stuff. It’s the same with radon. The goal of a suction pit is to create the most amount of pressure field extension. Soils often have little air pockets all over. Think of PFE like a spiderweb. When you dig your pit, you’re not really trying to attract the radon or get it to a gathering space. Instead you’re just trying to get as many connections as possible. Almost like a superhighway. You want your air pathways to connect to the entire sub-slab area and ensure that no soil gas will escape your fan’s influence.
Go big. In our tutorial video, you’ll see we suggest 3+ home depot buckets of debris removal. That’s 15 gallons minimum. Being unable or unwilling to dig a big pit is the biggest reason radon systems fail. Sometimes it’s due to ignorance or a lack of effort: this is hard work and requires sweat equity. However, sometimes with clay soil it’s logistically impossible. That means you may be having to dig 2-3 x more extraction points for a clay soil foundation than you would with a sandy soil foundation and connect them above slab to get PFE across the entire foundation…. maybe it’s time to call a pro.
PVC size matters too. Read this full article on why you want to go bigger and choose 4″ every time.
Tight soil = High Suction
Beware, high suction fans are powerful and often are on the “noisier” side. There’s not much you can do. If your builder didn’t plan for radon with clay soils, then sometimes you get stuck with the big, loud fan. At PDS, we try to only carry the best brands and the most energy efficient and quietist fans available.
The GX series by RadonAway is an excellent choice for high suction applications. Be sure to read our warranty terms before purchase.
The Rn4-4EC is the best reviewed fan we carry. This fan is a workhorse and extremely efficient. Read our testimonials for more.
Up next
Read up on fan curves and why they’re important
Read why focusing on getting a high vacuum pressure is the wrong way to look at things here.
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