Radon

I remember the big fuss about radon when it first came out (yeah, I'm that old) and since I'd really like to dig 3-4ft below grade (given we don't hit solid rock) so we're protected from weather by the earth, radon is something I've been thinking about a lot lately. So I thought I'd dig into it and research it now before we put more time and effort into design. I personally know of no one who has even done anything to reduce radon levels in their home, nor do they seem at all concerned about it. But every website I found that talks about it raises concern about its links to lung cancer. I have always wanted to have fresh air in my home, to bring what's outside, inside. Breathing in concentrated radiation isn't my idea of clean air.

My latest research into radon included an Ohio map of counties where homes were found most likely to test high for radon. The county in which we plan to build was among those in the red zone. :-(

 My guess is that the reason for such high numbers of radon-saturated homes is that the county we're moving to is a predominantly rural county and there are a lot of old houses that have crawlspaces with wood floors, or with unfinished basements where the mortar has cracked, some without any brick at all. Radon gas comes from the constant breakdown of uranium and radium in our soil - Ohio apparently has some quantities of it.

The problem with radon isn't that it gets into the home and we breathe it in. It's that most homes are airtight and the air doesn't flow through it very freely. In a lot of cases, there's a negative air flow in the basements caused by the furnace pulling in air to heat the house. That air sucks the radon gas from the basement walls and floor into the rest of the house and doesn't leave very quickly. Instead it gets recirculated through the air intake ducts, pulling dust in with it. Breathing radon gas directly isn't what's dangerous, because you just breathe it right back out, and it doesn't have time to do any damage to your lungs. The problem most modern homes have is that the radon settles into the dust, thanks to static electricity, which recirculates through the furnace ducts, then you breathe in the dust particles and the radioactive radon molecules that are attached to those dust particles that get lodged in your lungs will sit and decay - slowly releasing radiation into your lungs that can cause cancer.

Fortunately, the conditions that mitigate the concentration of radon into a home are inherently built in to natural home building's design.

To start with, there's the floor.

I included this image in another post earlier describing the kind of floor I wanted to build.

By laying down a vapor barrier on top the open, bare earth, we've already slowed down radon's release into the home considerably. We also intended to include a vapor barrier between the back-fill and whatever we use to build the walls (rammed earth tires, earth bags, can walls, bottle walls etc). When  I first considered doing this floor, I thought the vapor barrier might not be necessary. But considering Ohio's high radon output, I'd just rather do it than have to worry about it.

On top of the vapor barrier I want to put river rock, or large gravel, followed by layers of finer gravel. Initially this was to help distribute the heat (that is absorbed from the rocket mass heater) throughout the house. Now, I'm thinking of adding some open pipes near the outside edges of the lower regions of the layer with the largest gravel to facilitate some air flow.

Negative pressure usually occurs on the side of the house where the wind doesn't blow. In Ohio, most of the wind comes from the southwest. A few strategically placed (and screened to keep out critters) pipes on the northeast perimeter of the house, stretching from under the larger gravel to above grade, and capped with an aerodynamic cap (both to keep out the rain and to act like an airplane-wing to create more negative air pressure moving upwards), could gently draw out stagnant air from under the gravel. To prevent the negative air space (caused by the northeast pipes) from drawing in even more radon from the soil, a smaller number of pipes, with inclined, funnel shaped openings on the side of the house that the wind hits (the southwest perimeter), directed to accept the wind pressure, could force enough air into the gravel layer to replace the air being drawn out.

The two sets of pipes can create a gentle exchange of air throughout the floor gravel, letting the floor breathe, limiting not only radon build-up, but stagnant moisture accumulation as well. Combined with the heat from the rocket mass heater, any moisture that could travel between the stones would be gently carried away by the slow air flow. All this with zero expended energy.

Finally - since the home won't be heated through the transfer of forced warm, dry air through ventilation ducts, it's unlikely dust will accumulate the way it does in a traditional home. Fresh air will be brought in through pipes at the bottom of the back-fills. The temperature of the earth remains fairly constant at that depth - like around 50. In theory, the backfill would warm up the freezing, winter air and cool down the hot, summer air, so the air coming into the house would be regulated to a tolerable degree. The roof vent (we'll cover that in another blog) would release any warmed air through the roof, creating a negative air flow, pulling in the regulated air from the back-fill pipes. In winter, the rocket mass heater would be sucking in the air from the room to fuel the fire with oxygen, so that would also create a negative air flow to pull in the back-fill regulated air.

This regular exchange of fresh air should vent out any radon gas that would wander in - again, letting the whole house breathe. Combined with the oxygen/carbon dioxide exchange from planting edible plants in every available space in the house that receives sunlight, I think the air in our little space should be as fresh as a forest.