A Best Home Inspection, Professional Home Services
A family owned, New York Inspection and Radon Mitigation company serving Central New York.
Written by Tom Francis, Radon mitigation system designer and installation specialist. Updated 2/12/2018
There is no exact recipe or cookie cutter approach for Central New York radon mitigation. The variables of home construction and the geology of the soil beneath are many and very often not visible. I have seen a home with radon gas measuring over 100 pCi/L next door to a nearly identical house with less than 1 pCi/L. The same type of system will work in the same type of house most of the time, but not always.
Most of the time radon mitigation is straightforward and can usually be successfully mitigated in a single day with a basic system. But sometimes it can be more challenging, requiring extra steps, more time and expense than anticipated. With several hundred successful radon mitigation systems under my belt, I can say from experience, on rare occasion or about 2 houses out of 100 they can be very difficult or extremely challenging to mitigate. With this in mind, it’s always good to have a phased approach or a backup plan in mind just in case the simple or basic approach does not work as anticipated or hoped for.
I can say with confidence, all homes can be successfully mitigated to a radon level below 4 pCi/L and most can be mitigated to below 2.0 pCi/L. If you have a home with high radon, it is important for you to know that “some” radon mitigation jobs will take more work than anticipated and “some” radon contractors are not willing to do the required work needed or on the other hand, in these “difficult” situations, “some” homeowners are not willing to pay the additional expense required for the additional work needed and may settle for or end up with a home that is not mitigated to a satisfactory level. It is important to know the reputation of the contractor and for these contingencies to be clearly understood up front in the written proposal or work agreement.
The Basics, How to Reduce Radon
There are many method used for successful New York radon mitigation. Following are several of most basic methods used either individually or in conjunction with one another. Cost will vary depending on house design and details of system installation. Cost may or may not include post mitigation radon testing, which should always be performed after a radon system is installed to ensure proper operation of the system reducing radon to level below 4.0 pCi/L.
1. “Sub-slab Depressurization” Average cost $1100 to $1500
Sub-slab depressurization radon mitigation system basic components are displayed in Figure 1. This is the most common type of New York radon mitigation system, considered the most effective method of radon mitigation for most homes throughout the world; that is for most homes with concrete floors in basements, crawl spaces and slabs on grade.
The basic features consist of a hole is drilled through the concrete floor where a small suction pit is formed by removing 3 to 5 gallons of soil and or gravel. A radon fan pulls radon gas laden air from under the floor, effectively depressurizing the sub-slab soil. through a PVC vent pipe; the fan is usually mounted in an attic space or on the exterior of the structure (Figure 1. shows both options); the radon gas is safely discharged through the vent pipe at least 10 feet above the ground, away from windows, in most cases the termination of the vent pipe is either through the roof or above the side of the roof. Source for picture: EPA/625/R-93/011, Page 8, October 1993
2. “Drain Tile Depressurization” Average Cost $1100 to $1500
Drain Tile depressurization radon mitigation system is a variation of the sub-slab depressurization system that works well for newer homes built after 1970 that have interior footer drains or a sump pit present. In Figure 3. it shows a hole is drilled through the concrete floor above the interior footer drain pipe. This is often the best option if a sump pump is present, especially if there is more than one sump pump (many sumps have two or three pumps present). Source for picture: EPA/625/R-93/011, Page 10, October 1993
3. “Sump Cover Depressurization” Average cost $1100 to $1500
In Sump Cover depressurization the radon suction point can be taken from the sump cover if there is no sump pump or if there is room on the cover. Multiple sump pumps and a radon suction point and floor drain if needed all present in the air tight sump cover can make for difficult removal of the cover for service. In either case the sump will generally need to be sealed with an air tight cover in order to depressurize the sub slab area.
Generally speaking it is best not to use the sump cover if there is more than one pump, or if the sump needs regular maintenance. Radon mitigators will sometimes use the sump cover for suction because they don’t have to drill through the slab, but it often over crowds the sump cover causing function and service issues. The radon gas is safely discharged in like manner to the above systems, through the vent pipe at least 10 feet above the ground, away from windows, in most cases the termination of the vent pipe is either through the roof or above the side of the roof. Source for picture: EPA/625/R-93/011, Page 193, October 1993
4. “Sub-membrane Depressurization” Average cost $1300 to $2000
Sub-membrane depressurization is used to mitigate radon soil gas from dirt or gravel or solid rock basement and crawl-space floors. With poured concrete floors we are able to suck air from below the concrete, but when there is no concrete floor we either need to pour one or cover the dirt, gravel or solid stone with a radon proof barrier sheet that can trap the radon so it can be pulled out with a fan. Some mitigation contractors use single ply poly sheet, usually at least 6 mill thick, this material is only good for a short time before it begins to crack and deteriorate, rendering the radon mitigation system ineffective.
We use 24-mil. radon barrier waterproofing membrane; made from tough, durable, high-density polyethylene (HDPE), that provides superior radon barrier and moisture protection for all types of foundations in residential basement and crawl-space applications. This material is suitable for foot traffic or storage and you can install poured concrete or wood flooring over top. In other applications we use high quality and long lasting 3 ply, nylon scrim reinforced, laminated poly sheet that is 6 mil or greater thickness in difficult to access crawl-spaces.
There are a multitude of methods used (in addition to those shown in Figure 6. to seal radon barrier sheet at the floor edges, walls and rim joists, depending on the condition and type of foundation wall materials.
5. “Sub-slab Pressurization” Average Cost $1100 to $1500
Sub-slab pressurization radon mitigation systems is basically the same as a sub-slab depressurization radon mitigation system with the main difference being, the fan is reversed and is blowing air under the slab instead of sucking. In this case the positive pressure of the forced air prevents the radon from coming up into the home. This type of system is usually not a first choice for New York radon mitigation systems but is sometimes used when negative pressure does not give desired results. In cold weather climates like New York, the concrete floor can become quite a bit colder that normal with this type of system and may cause an increase in heating costs.
6.0 “Positive Pressure Ventilation” Average Cost $1500 to $2500
Positive-pressure ventilation systems, blow fresh air into the house and in cold climates can be combined with a heat exchanger (HRV) to recover energy in the process of exchanging air with the outside. These systems are being put into many new homes for improved indoor air quality, with the added benefit of reducing trapped radon. Exhausting basement or first floor air to the outside is not necessarily a viable solution as this can actually draw radon gas into a dwelling, making it worse. Homes built on a crawl spaces however can often lower radon be increasing fresh air ventilation to the crawl space and placing a vapor barrier or “radon barrier” (a sheet of plastic that covers the crawl space), that is sealed at seams and at the wall.
Summary – The Basics of New York Radon Mitigation
Simply put radon gas follows the path of least resistance. Typically radon gas is sucked into a home by a small amount of negative pressure existing in most homes. Negative pressure is common in most homes (also referred to as the stack effect) and is usually greatest when homes are closed for the heating season. Radon gas is also trapped in homes during summer if closed up and running the A/C system. However with that said many homes have high radon levels even with windows open for fresh air ventilation.
The small molecules of radon gas can easily pass right through solid concrete even if no cracks are present. Sealing the cracks and gaps and holes in the floor is rarely enough to significantly reduce radon gas level in the home. A basic radon mitigation system pulls the radon gas from below the basement floor or radon barrier sheet before it enters the home and vents it to the outside air. The suction below the floor or sheeting created by the radon fan is greater than the negative pressure that normally exists inside a home.
High radon levels tend to be more of a problem in newer, more energy efficient homes. In a well ventilated home or an old drafty house, the radon concentration tends to be very similar to the outdoor level and usually does not pose a problem. Unfortunately one of the drawbacks of a highly insulated, “air sealed”, energy efficient home is very little fresh air circulation. Tightly sealed, energy efficient homes can trap radon gas causing it to build up to undesirably high levels.
Radon levels in indoor air can be lowered in a number of ways, from simple methods of sealing cracks in floors and walls to increasing the ventilation rate of the building. These simple techniques, alone, most often are not effective at lowering high levels of radon but can prove to be adequate if the radon level is slightly elevated. Remember that small radon molecules can travel through concrete once cracks are sealed.
Five principal ways of reducing the amount of radon:
- Improve fresh air ventilation, easy but not always practical.
- Installing a radon fan as part of a sub-slab depressurization system or other type of active fan radon system.
- Sealing floors and walls, beware that this alone will sometimes elevate the radon level.
- Installing a positive pressurization or positive fresh air supply ventilation system, while not technically a radon mitigation system is often effective at lowering the radon level.
- For new construction – radon resistant construction and or a passive radon vent pipe tied into drain tile system for basements
New York Radon Mitigation, Making Homes Safe
Since there is no “safe” level of radon, the our goal of when we design a New York radon mitigation system is to lower the level of radon gas as much as practically possible. We guarantee that our systems will achieve an average radon level less than 4.0 pCi/L which is the EPA action level and considered acceptable for most real estate home sales. Most systems we install achieve radon levels less than 2.0 pCi/L. These are the two radon action levels set by the EPA. Note: the EPA suggests you may want to consider radon mitigation if the average radon level is 2.0 or higher in some cases, (ie when occupants especially toddlers or children home all day, and or playing on or near the floor).
The World Health Organization is recommending that homeowners take action to remediate the radon level in their home if it exceeds 100 becquerels (Bq), which corresponds to 2.7 picocuries per liter (pCi/L). That’s lower than the 4.0 pCi/L current action level in this country as recommended by the U.S Environmental Protection Agency.
ASTM E-2121 is a standard for reducing radon in homes as far as practicable below 4 picocuries per liter (pCi/L) in indoor air. The EPA has also set 4.0 pCi/L as an action level, when the average radon is 4.0 pCi/L and above, in the living area of the home, the EPA recommended to take action to lower it.
If you live in Central New York, call “A Best Home Inspection” for a free New York Radon Mitigation Evaluation and written estimate – Call Tom Francis at 315-439-1103 or email at firstname.lastname@example.org