ICF home with elevated radon
Here’s my situation:
– 2150 SFT ICF ranch with full basement (partial walkout) in East-central Illinois with EIFS siding.
– Exhaust-only ventilation thru 3 bath fans (2 on the main floor plus one in the basement that we rarely use) and we can feel the fans struggling to get the air out due to tight ICF.
– Large windows on the pond-side that are double-paned but we can feel cold air drafts on the insides of the window sill sides. When I complained about this, the builder sent me some foam stoppers to install for the winter time which seems to help some.
– 2 adults and 3 children mostly using the main level, the basement just for recreation.
– Humidity issues in the basement during summer so I blocked-off some of the return registers on the main floor to force the HVAC to draw almost all of the return air from the basement so it gets dehumidified by the AC coils. This seems to work and so I left the blocks in place for the winter as well.
– Misture condensation on the windows during winter.
– 3-day Radon test by a Radalink tester shows 6.3 pCI/l in the basement.
1. Is negative pressure created by exhaust-only ventilation to blame for both of the issues? I am thinking if somehow positive pressure is introduced, there won’t be much infiltration from the outside at the window sills and it will also help keep radon not seep in in the first place.
2. Or does an HVAC in an exhaust-only ventilation setup somehow generated positive pressure by forcing air in thru leaks, cracks and such, and so that’s what’s causing the infiltration at the windows and radon thru the basement floor?
3. Any inexpensive way to measure the delta P?
4. Would adding a passive air inlet (say in the dryer closet) help with undesirable infiltration at the windows and radon/basement floor? Are these inlets really only one-way as the name suggests or do they let air to the outside as well? Don’t they have some minute dampers on them prevent the reverse flow?
5. Is an HVAC capable of sensing that the positive pressure has dropped and can it then automatically start off by bringing outside air in via an automatic damper controlled duct connected to the return duct?
6. I have also heard about HRVs. Are they capable of generating the desired slight positive pressure? IOW, can they be adjusted to bring in more air than what they let out? In the extreme case can I simply shutoff the exhaust side of the HRV? I realize they can’t keep up with the dryer and the central vac. We don’t have a kitchen exhaust.
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