Questions about radon mitigation
Hi All! New homeowner and new to this forum. I have been doing a lot of research on radon since buying my first house last fall. The results of the inspection showed I had a 4.2 pCi/l radon level. I believe this was a short term test and so I had a long term tested performed to see the "actual results." This came up with nearly the same results (4.6 pCi/l). I know the level isn't too high, but it is above what is recommended. So, I'm going to do something but am hoping to get a few questions answered first.
1. What is the easiest way to determine how much cfm is needed? I have a Split-Level 1800 sq. ft. home, 700 basement, 500 Main and 600 Upper Level. My sump pit is in the crawl space with a fairly easy exit point, except for a deck on one wall. Therefore, I would rather run the pvc a longer distance (15-20 ft, 2-3 elbows) and exit out the back since I plan on extending the deck to the front of the house as well. All the radon fans I see don't have very high cfm ratings, but have a high inches w.c. reading. I assume this is because it just needs to create a "better" negative pressure reading than the house does? I have an HRV and a new 90+ furnace that brings its own make-up air in, so my house shouldn't be too negative???
2. What is the better procedure; Mounting the fan inside or outside, and why?
3. This brings up another question; Is there a reason I couldn't terminate the pvc out the wall (fan inside) and not above the roof line?
I'm sure I am forgetting something but for now this will do. If any of you can help me, I would appreciate it!