Frequently Asked Questions
Isn’t radon just a hoax?
When it comes to the dangers of radon, there is overwhelming consensus that it is a grave public health hazard that needs to be addressed. The following organizations have all taken positions that the public should test for radon in their homes then remediate if they have levels over 4.0 pCi/L.
- United States Environmental Protection Agency
- Centers for Disease Control
- United States Surgeon General
- National Institute of Health
- National Academy of Sciences
- United States Congress
- National Environmental Health Association
- American Lung Association
- American Medical Association
- World Health Organization
- National Radon Safety Board
What is a safe radon level?
There is technically no safe radon level, since one alpha particle can theoretically begin the chain of events that leads to lung cancer. Our goal is to reduce radon as close as possible to the average outdoor level of 0.4 pCi/L. Almost 90% of the homes we mitigate re-test between .5 and 1.5 pCi/L. Our guarantee is always to below 4.0 pCi/L at a minimum. Many houses can be guaranteed to below 2.0 pCi/L, but not those with long-term radon levels exceeding 6 -7 pCi/L.
My new home came with a builder-installed passive radon system, is that good enough?
Frequently the answer to this question is no! In many cases, even a perfectly constructed passive radon system (and we don’t see many of these!) will not necessarily reduce radon levels sufficiently (below 4 pCi/l) due to the strength of the emanation of radon into the house. Radon is slightly heavier than air and generally won’t go up through the vent pipe by itself. In these cases, we can install a radon fan on the vent pipe in the attic to effectively reduce radon levels in the home.
Passive radon systems usually consist of a 3 or 4 inch PVC vent pipe that is sealed into the gravel layer under the basement slab or into a sealed sump cover which runs from the basement up through the home, into the attic and venting through the roof. The theory of a passive system is based on thermal stack effect, which causes a house to act as a vacuum on the soil due to temperature differences inside and outside the home.
The passive radon vent pipes are often obstructed when set in the slab, rather than the sump cover. There are various reasons: maybe the pipe was stuck down to far, into the dirt below the gravel, or the gravel is very compacted, small diameter stone, with lots of dirt and sand in it. That presents very little porosity under slab, making it difficult to create good air flow (vacuum) across the entire slab. In those cases, we have to re-configure the vent pipe into a new slab penetration with an open air space beneath it in order to be able to guarantee results.
A passive system’s vent pipe should ideally be run through one of the combustion appliance chases (furnace or hot water heater) that run from the basement to the attic of a house. The heat inside these chases may create a vacuum in the vent pipe, but ONLY if the following conditions exist:
- The floor-to-wall joint and all other basement slab openings, such as sump crocks are completely sealed during construction, with a sealed vapor barrier under the concrete
- The vent pipe has no completely horizontal runs and minimal bends.
Even then, the passive systems cannot overcome high emanations of radon. Thus, the fan:
There needs to be at least three feet of accessible, vertical vent pipe in the attic for us to convert a passive radon system to an active system. That’s the minimal vertical space needed to fit the fan with couplings. Unfortunately, we find Builder’s plumbers frequently make the mistake of jamming their vent pipe into the soil beneath the concrete slab (thereby making it useless by blocking it), venting the radon out the side of the home at or just above ground level; Sometimes they retro-fit the pipe in the concrete AFTER construction because they didn’t realize it was required (as in Montgomery & Howard Co.s, among others) and only find out in the final inspection. So we encounter a radon vent pipe, jammed down into a shallow hole in the concrete and completely blocked.!
Test you home! Even if you have a “passive” system. There is a very good chance that your builder-installed, passive radon system has not sufficiently lowered your radon levels.
Can’t I just caulk and paint my basement and solve my radon problem?
Painting and caulking alone will not effectively lower radon levels. This is because the suction or stack effect exerted by your home on the soil draws radon through so many minute openings that you could never seal them all. Regardless, emanates through semi-porous materials such as cinder blocks and concrete.
How much does a radon mitigation system cost?
The average cost of a radon system is between $800 – $1200. Homes with a crawl space, no gravel under the slab, or a completely finished lower level, a garage attic installation, etc. cost more.
How much will it cost to run?
About as much as leaving a 75 watt light bulb on 24 hours a day, which depending on where you are located, should be less than $100- $125.00 per year.
How long will it take?
Installing a complete radon system usually takes between three and five hours.
My neighbor had a low radon test result, so I am okay, right?
Wrong! Radon levels vary widely from home to home, depending on the geology around and beneath your home and the home’s construction. Also, the neighbor’s house may not have been tested properly. The only way to know your level is to properly test your home.
Are radon systems expensive?
That really depends on the type of structure we’re talking about and what the regulations are in your local community. Typically, it falls between $800 and $2000.00. If it’s a new home with, the passive piping in place, it can be less, That varies depending on the code requirements in any given jurisdiction. In our area, Montgomery, Howard, Frederick, Carroll, Calvert and Baltimore Counties currently require passive radon vent pipes in new construction. There are no current code requirements for this in VA.
If we once had a radon reading below 4 pci/l. (Ideal) but now it’s at 10 pci/l, what has happened? Do we need radon remediation?
Radon levels are always changing. Seasonality can play a role – winter is worse than summer due to the heating of the house. The heat rising in the house creates a stronger vacuum on the soil. Time of day (the diurnal effect) also plays a role, as well as the weather situation, wind levels, etc. Prolonged periods of windy, rainy and snowy weather cause prolonged spikes; so in our climate, winter time radon levels are usually significantly higher than the summer. The cooling of the house in summer reduces the vacuum on the soil. If you consistently have high levels over a period of time, or if you get a result above 4.0 pCi/L in summer, you probably need to move forward with mitigation.
When building a new home what can you do to reduce the risk of a radon problem or eliminate radon remediation?
First, know that it is impossible to determine how much radon a new home will attract. Every house has what’s called a unique pressurization signature. This is the result of the heating, ventilation, plumbing and drainage systems working together. This all affects the vacuum created on the soil.
Here is some general advice when building:
- The integrity of the slab should be maintained at all times.
- Cover sump pits; close the openings around sewer and water piping.
- Reduce radon infiltration by increasing ventilation.
- When framing, route a radon pipe from the basement to the attic.
Are there less expensive solutions for Radon Remediation?
Although simply sealing cracks and joints, sumps and other slab openings can have some effect, that alone is generally not a certain or permanent solution.