I live in a house built in 1947. Full basement, poured walls. There is a sump for the skirt/under floor drain open in the basement.
When a neighbor sold their house, an inspector identified radon in their basement. The inspector suggested the source of the radon was the sump in their basement for the skirt drain. They installed a positive ventilation system complete with a hole through their poured wall, 4in pvc to the roofline, and a 150 watt fan operating 24/7 to vent the sump for their perimeter drain.
My basement also tested positive for radon.
I have reservations about duplicating the neighbor’s system: 1) the continuous draw draw of electricty can add up, 2) the vent is taking heat up the stack, 3) the vent creates a vacuum in the house. The windows in this old house do not require additional encouragement to leak cold air in the winter.
I would enjoy comments on an alternate solution: create a gas tight seal for the sump; connect the sump to the sanitary sewer (gas tight) including a downward leg before taping into the sewer to be certain that no wastewater could back-up into the skirt drain. Use no blower.
Radon (Rn) is heavier than air. By my calculations about eight times. (9.73 g/l for Rn vs 1.2 g/l for air). Since the sanitary sewer should have air space above any flowing liquid, the heavier Rn should flow in the air space above liquid in the sanitary lateral to the sanitary sewer in the street, then vent at manholes to the same atmosphere as my neighbors powered vent. Water in the drain traps at all drains to the sanitary sewer should prevent Rn from entering the living space in the event wind would cause gas flow from the sewer out the vent stack of my house.
(Sewer maintenance in my community always includes positive ventilation with gasoline powered air blowers (including propane heaters in the winter) so my Rn would not be ‘poisoning’ the sewer repair workers. )
The advantage is no power drain, no blower to maintain, and no cold drafts in the house.
Before I construct this system, I am interested in perspectives of whether the solution would effectively, and safely vent radon.
There may be possible responses including reference to a ‘code’. Without intending to be ungracious, not everything in ‘the code’ makes sense. If a code has something to say on the subject, is there also an explanation of why?
Happy holidays,
Anwalt
Replies
When I moved in to my new house, it also tested positive and I got an under slab system. I did some research at the time; hopefully my recollection is correct. First, while I'm sure the sump offers an easy path, I've been told that radon can travel through the concrete slab so I'm not sure your sealing idea is going to do the job. At the very least it seems likely that there will be some cracks in the slab or around the edges. It would probably help this discussion if you post the results of your test.
Draw from a typical radon pump is in the neighborhood of 60-90 watts (mine is 70).
I'm curious about your neighbor's house. It sounds like they didn't do a sub-slab system there. The sub-slab system is designed to maintain negative pressure under the slab to reduce radon entering the house. As near as I can tell, there's some, but only very little air being drawn in mine. I'm told that the sub-slab approach depends on what's under the slab; my house is relatively new so the slab is poured over crushed stone. I'm sure some of the gurus can help out on this.
Radon is also a topic that brings out extreme opinions on both sides ("radon is incredibly dangerous" vs. "radon is fearmongering"), so be ready.
I recently built a guest house for a client in the state of NJ. Code did require a vapor barrier under slab with a 4 inch P.V.C. vent up thru the roof; but did not require a fan. The guest house was tested for radon and passed with nary a trace. The main house (with full basement) has a radon system with a fan running 24/7 and still has borderline levels. The guest house has a three ft. crawl space with a sealed sump pit.
Did my system work? ..or did my excavation avoid the same radon field infiltrating the main house 150 ft away?
Have you done a long term test? They're cheap.