What will a radon mitigation system cost you? What are the drivers for those costs?
If you have a radon problem in your home you will need to reduce the amount of radon in the air in your house. This radon removal process is called mitigation.
For radon the mitigation process is fairly simple. You are preventing radon from entering your home via your basement floor. There are two basic ways to do this. Either you seal your floor better than it is currently or you intercept the radon gas before it has a chance to penetrate the floor.
Sealing the floor is often part of the treatment. Lots of basements have large cracks, and these cracks can be a place of entry for the radon gas. Plus, if you are going to intercept the gas you can’t have large cracks in the floor. You’ll just end up sucking the air out of your basement while leaving much of the radon untouched.
Sealing the floor primarily means caulking cracks, but it can also involve sealing the concrete itself, to reduce the permeability of the concrete.
Sealing is a cheap solution. If all it takes to fix your radon problem is to seal the floor then you have gotten off cheap. This might work if your radon levels are just above the EPA’s threshold level of 4 pCi/L.
It is when you take the next step and try to intercept radon gas that you are really talking about a “system”. Intercepting radon involves pumping air out from below your basement floor.This makes the air pressure below your basement floor lower than the air pressure inside your house so that the air inside your house seeps into the space below the floor. This reverses the normal flow whereby radon gas seeps into your house.
Of course there is no open space underneath your basement floor. Beneath the concrete is either gravel or dirt. Depending on when your house was built you might also have layers of plastic or insulation. Unless your house has a crawl space there is no layer of air, but you will have tiny voids within the dirt or between the gravel. A radon mitigation system will pull the air out of a sump hole. To the extent that the voids are connected this will pull air out from under the concrete and into the sump hole to replace the air already evacuated.
In order to calculate the radon mitigation system costs lets look at the components of such a system.
1) Radon Pump
3) Wiring for the pump
4) Holes (in the basement floor, and in the walls to route the plumbing to the outside)
That is basically all there is to such a system.
Of these items the pump will be the most expensive individual item. If you were purchasing a radon pump on the internet you would expect to pay between $100 and $300. A radon pump is essentially a large fan in a sealed housing, with lots of noise insulation. The cost of the pump is proportional to the size. The size of the pump will depend on the size of the footprint of your house and the material below your poured concrete floor.
If you have a house built within the last 7 decades or so your concrete floor was poured over a layer of gravel. That layer of gravel is probably going to have large voids, so pulling the air out from the gravel only requires a small pump. In the case of an older house, like mine, the concrete was poured directly over the native, sub-surface soil. In my case that is hard-pack clay. Drawing the air out from clay is more difficult, so it requires a larger pump.
Thus the biggest factor in determining your radon mitigation system cost is the material directly beneath your concrete.
Also affecting your pump size is the total area of your basement. A 5,000 square foot basement will require a lot more pump than a 500 square foot basement. It may even require multiple pumps.
The configuration of your basement is also a cost driver. Some basements consist of a single slab. Others have interior foundation walls that are deeper than the basement floor. These break up the sub-floor area into separate zones. If air cannot move along the area beneath the floor to get to the sump, the multiple sumps may be required. These won’t necessarily require additional pumps, but they will require additional piping and another hole in your floor, and beneath the hole someone will have to dig out a sump. All of that represents additional costs.
Consider my house. The kitchen was built later than the rest of the house. The floor of the basement area underneath the kitchen is outside the main foundation walls of the house. This room had to have its own sump or else I was going to have one room with high radon levels. It shares the same pump as the rest of the house, but it still required an extra couple of hours labor to drill through the concrete and dig out the sump.
The cost of wiring the pump is usually not a big cost driver. The pumps operate off a standard 110 V circuit. The load is not all that large so that usually the pump can be wired into an existing circuit. If this is not the case and the pumps need their own circuit then the cost of the system might run a few hundred dollars higher.
These radon systems use standard PVC pipe to pump out the air, but it does require a 3” pipe. How much pipe is required will depend upon how many sumps are required and their location, and how the pipe is vented to the atmosphere.
By code the pipe cannot be any closer than 10 feet from a window. For most houses this means that the pipe has to be vented above the lower edge of the roof. In my case I lucked out. My kitchen roof is only one story high and by venting at the one corner I was able to be more than 10 feet from any window. If I had needed to vent above the roof over the main house then I would have had to run about 12 feet of additional piping and the installer would have had to bring the larger ladder and gone to additional effort which would have found its way onto my bill.
As a cost factor it really wasn’t that important. The main benefit of venting off of the lower roof was aesthetic. Going up an extra floor would have made the pipe that much more obtrusive.
It is possible to have a radon system that avoids the cost of a pump. This will significantly lower the cost of such a system, but these are usually only feasible for new construction. Such a system might only add about $300 to the cost of a house.
In most cases, for installations into an existing home, the radon mitigation system cost will be in the $1,000 to $1,500 range.
My radon mitigation system cost me $1,100 installed. I estimate that the components alone, if I were to order them over the internet or buy them at Lowes, would have set me back about $500. I should have been able to get the pump for about $250. The piping would have been the next largest item, with most of the cost being the connectors.
However I would have had some extra costs, such as renting a jackhammer, and buying concrete bits and I might have had to buy an impact drill. And somewhere in there I have to factor in the inexperience costs. I surely would have made some mistakes in the plumbing that would required me to redo some of my work, wasting time and materials in the process.
In retrospect I paid about $600 for someone else to do the labor and make the mistakes. Having seen the work done I would now feel comfortable doing it myself, but I still think it is a good idea to have it done professionally. When it comes time to sell the house there will be an engineering inspection and probably a radon test and it will be less likely that there will be concerns with the radon system if I can show that it was installed professionally.
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