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By chance I saw that there are a lot of radon questions here and it got me thinking:

Do I need to concern myself with potential radon levels when planning to build a new house? My question is based on long-term health considerations, and not so much any legal requirements. I plan to live there the next many decades.

Construction-wise, I have these specs:

  • For cost reasons, the house would be built without a basement (just a concrete-slab foundation) and without those cool newfangled active-ventilation systems.
  • Local laws require the house to be certified airtight.
  • There will be floor heating, so no radiators to create natural convection.
  • There will be a gas furnace that is independent of room air, so no air exchange there either.

I've read that radon seeps through the house from below, and the house need to be ventilated in order to get rid of the radon. Does this apply only if you have a basement, or always to the lowest floor in a building, or to every room in the building? What is the principle here?

I don't know what the radon levels would be in my area (Vienna, Austria), nor how to find out about this.

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Not by any planning permissions it does not need to.. –  ppumkin Feb 29 '12 at 14:01
Depending on where you live, there should be soil samples and other environmental studies done before breaking ground. These tests should reveal what's in the ground, and what you'll have to deal with. –  Tester101 Feb 29 '12 at 14:24
There may be maps showing detailed areas of radon discovery or likely areas to have radon. Check with your version of Geographic Studies. DEP in the USA. –  shirlock homes Feb 29 '12 at 20:56
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5 Answers

up vote 9 down vote accepted

You should consider, but not invest now. Wait and test, before treating. Small design changes now, can make implementing a fix later, easier.

Radon is everywhere, to some level. If you have higher levels of radon, then you need to be concerned with the rate that fresh air is exchanged in your home. Houses are much tighter today, so be more aware with a new house.

Many factors affect where radon collects. Do you heat with wood? That moves air around your woods stove. Do you have leaky windows? That exchanges small amounts of air all over the house.

To get a general sense, ask a few neighbors if they have tested for radon. On the other hand, I have rock under my house, while my neighbor has sand, so things can vary quickly. You could call a few local excavators, or well drillers, as they are likely to have a guess. Fill (the dirt and stone under your lawn) gets moved around so much, that you can't rely on historical or nearby testing.

Your local building inspector is probably going to be your best resource. And since you're going to be seeing that person alot anyway, you might as well make contact.

Let's say you have a concrete slab, with stone under it. Whether or not this is a basement doesn't matter. Your builder will put a layer of plastic under that, to keep out the "rising damp", and it may help limit radon. It would be a simple thing to ask for 8 feet or so, of perforated pipe, capped, to be placed under the slab. In the middle, have a 90 with a pipe come up through the concrete into your house. Cap it for now. $20. When you test later, it may be enough to stick a bath fan on it, and pipe the air outside. Cold ground air is simply piped outside, and radon may not collect.

If you are putting in ducts for heating/cooling, ask about how an HRV could be attached. I think this is the ventilation you were thinking of (heat recovery ventilator). The HRV is about $1k, and could be bought later. The ductwork is hard to do later.

In addition to air quality, you may also want to check on radon levels in your water, if you have a well.

Cost reduction is good. Basements are often incorrectly drained, so can be damp and harbor mold. On the other hand, if you put in good drainage, basements are cheap square footage. You might consider reducing closets and rooms and keeping the basement.

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Thank you for a very detailed answer! I think you're right that the local building inspector would know. I put it on my list of questions. By the way, we won't have a well, just tap water from the public water works. –  Torben Gundtofte-Bruun Feb 29 '12 at 18:49
Regarding cost reduction, high ground water seems to be a big problem in my area, so avoiding a basement avoids costs to make the basement water-tight and also avoids all imaginable water-related problems. Because of the water-proofing, adding a basement is pretty much the most expensive way to add space (when counted as euros per square meter). It's much cheaper to add a big(ish) garage. But I'm not sure I'll be able to afford even that. And we've already reduced the size of our planned home as much as we can. –  Torben Gundtofte-Bruun Feb 29 '12 at 18:53
Good call on the no-basement then. Sealing your basement is like building a boat, and you have to deal with the water pressure. You need to be able to remove water, to put in a basement (or accept occasional flooding) –  Brian Maltzan Feb 29 '12 at 19:20
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There are plastic-sheets available for putting under the concrete-foundation of a house that are long-term radon-safe, i.e. that won't let radon trough even after several decades. Putting such a sheet under the foundation is low-cost and easy, and I don't see any reason -not- to do so.

Pay attention that you don't perforate the sheet with pipes/wires/whatever as it needs to be intact to work.

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In the UK, phone up your local building regs department and they will tell you if it is an issue in your area.

The sheets you put under the floor slub to stop radon are relativity cheap, is if there has been any issues in your area, it may be cheaper not skip the tests.

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Ethically? Legally? It all depends, I guess.

Radon is linked to cancer, so if you care about not getting cancer, and are planning on living there, I'd look into it.

Basements are more of a problem as are 'tight' houses due to lack of air exchange.

We had our old house with a basement retrofitted for Radon for about $1500. I imagine it'd be significantly cheaper without a basement and especially when planned for pre-construction. The cost shouldn't be that much if it's needed.

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"if you care about not getting cancer" :) yeah I think I do! Modern houses are a lot more airtight than old ones; they must be by law, at least in Austria. If the house is not airtight then it's poorly insulated and then I won't even get the building permit... –  Torben Gundtofte-Bruun Feb 29 '12 at 18:33
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If you are in an area with granite rock (there are other indicators of Radon, but granite is the most common) then you should get a soil survey done. As @Tester101 said, results may already exist for your area, so check this first.

If the results show high radon levels, definitely get ventilation fitted - this is important for basement levels, but you should be able to get guidance for higher floors if radon levels are high. Speak to other home owners in the area to see what they have had to implement.

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