Pikaqu wrote: ↑ I believe that HRV is better solution than radon fan for reducing radon level in the house.
Radon fan draws air from sump pit and weeping tile. some percentage of the exhausted air are from the house, creating negative air pressure inside the house. outside air will be drawn from all leakages of the house. Radon fan also prevent radon getting inside of the house by sub-slab depressurization. If the slab is not air tight, I doubt you can create a consistent negative pressure under the whole area of the slab.
HRV maintains the inside/outside pressure balance. Outside air is drawn only from the fresh air intake. It's energy efficient way of ventilating, because of the heat recovery.
There has been many past radon mitigation discussions suggesting the use of a dedicated HRV for the basement only, where 100% of the basement air near the ground is exhausted outside while the fresh outdoor air is drawn directly into the basement as well. Some folks also modified their existing HRV to draw basement air rather than air from the return vents. These HRV methods seem to work as well, but the bottom line is that radon has already entered the home and you're trying to remove radon from inside the home. Sub slab depressurization is "viewed" as a more desired solution because it supposedly prevents radon from entering the home in the first place. However, you are correct in that slabs can have cracks and such where negative pressure in the basement might cause radon to enter through cracks from the side of the house instead.
So yea, everyone's basement is different. With sub slab, it's tried and tested to work the majority of the time as long as radon is removed faster than it's seeping into the basement (and before being sucked up by furnace and HVAC into other parts of the house). With HRV, the air intake with fresh outdoor might need some experimentation where the outdoor air is blown directly in the furnace direction, and the exhaust port is located at the opposite corner of the basement to allow the air current to catch the lingering radon in the basement.
At the end of the day, how much money you got to play around? You try one, and if it doesn't work, you try the other...
By the way, most homes in my area within GTA are built in the past 20 years or so, with the vast majority not having or requiring a sump pit.
In addition, no slabs are airtight and every basement has cracks in the walls or floor.