There are several methods a mitigator can use to reduce radon levels in your home. While the most effective approaches prevent radon from entering your home, others methods reduce radon levels after it has entered the home by diluting the high radon air with clean air. EPA generally recommends techniques that prevent the entry of radon.
Active soil depressurization, for example, prevents radon from entering your home by drawing the soil gases from below the homes foundation, and venting it through a mitigation system made of PVC piping, to the air above the home, while at the same time, creating a negative pressure relative to the basement, making it difficult for the soil gases to enter into the home.
Any information that you have about the construction of your home, could help your mitigator choose the best technique. The mitigator will perform a visual inspection of the home, and design a custom system that considers specific features tailored to your home. If this inspection fails to provide enough information, the mitigator may need to perform diagnostic tests prior to the installation to help develop the best radon reduction system for your home. For example, your mitigator can use a smoke pen to find the source and direction of air movement and drafts. A mitigator can see the air flow sources, and directions, by using a small amount of smoke that they shoot into holes, drains, sumps or along cracks & other potential openings, like plumbing. The sources of air flow show possible radon routes and entry points. A trained mitigation may have concerns about combustion appliance backdrafting, which should be considered in every ASD installation, and may recommend the homeowner having the appliances checked by a qualified inspector.
A soil communication test, or PFE (pressure field extension) test, is another diagnostic test frequently used in radon mitigation. This test requires a vacuum cleaner and smoke to determine how easily air can move through the sub-slab material under the foundation. By putting a vacuum cleaner hose in one small hole and using smoke in a second hole, a mitigator can see if the smoke draws down into the second hole from the vacuum cleaners suction. The communication test helps a mitigator decide if certain radon reduction techniques would work well in your home, and helps determine the proper equipment to maximize efficiency incertain situations.
Whether these tests are needed is determined by details specific to your home,such as the foundation type, the material under your home, and by the mitigators experience with similar homes and similar test results.
Your home type will be the deciding factor for the kind of radon reduction system that will be most efficient. Homes are typically categorized according to their foundation structure.
For instance: basement; slab-on-grade, concrete poured at ground level; or crawlspace, a shallow unfinished, unconditioned space under the first floor. Some homes have more than one foundation design feature. For example,it is common to have a basement under part of the house, and to have a slab-on-grade or a crawl space under the rest of the home. In these situations a combination of radon reduction techniques might be needed to reduce radon levels to below 4 pCi/L.
Radon mitigationsystems can be grouped by the home’s foundation design. Find your type of foundation above, and read about which radon reduction systems would be the best fit for your home.
In homes with a basement or a slab-on-grade structure, radon is typically reduced by one of these four types of soil suction:
Active sub-slab suction also called sub-slab depressurization is the most common and typically the most reliable radon reduction technique. One or more suction pipes are inserted through the concrete slab into the sub-slab material (crushed rock or soil)underneath. They also may be installed below the concrete slab from outside the home. The number and location of suction points that are needed depends on how easily air can move through the material under the slab, and on the strength of the radon source. Typically only one suction point is needed.
A mitigator usually gets this information from visual inspection, diagnostic tests, and experience. A radon fan connected to the suction pipes draws the radon gas from below the homes foundation,and releases it into the outdoor air above the roof, while simultaneously creating a negative pressure beneath the slab. Fan are commonly located in unconditioned home spaces and garages, and sometimes the exterior of the home.
Passive sub-slab suction is the same as active sub-slab suction, except it depends on natural pressure differentials and air currents, instead of a fan to pull radon up from below the homes foundation. Passive sub-slab suction is usually associated with radon resistant features installed in new construction.Passive sub-slab suction is typically not as effective in reducing elevated radon levels as active sub-slab suction.
Some houses have drain tiles, or perforated pipe, to direct water away from the homes foundation.Suction on these areas are often effective in reducing high radon levels.
One variation of sub-slab and drain tile suction is sump-hole suction. Often, when a home with a basement has a sump-pump to remove unwanted accumulating water, the sump can be utilized so that it can continue to drain water and serve as the location for a radon suction point.
Block-wall suction is a technique can be used in basement homes with a hollow block wall foundation. This method reduces radon by depressurizing the block wall, similar to sub-slab suction. This approach is often used in combination with sub-slab suction.
In some cases radon levels can be reduced by ventilating the crawlspace passively, or actively with a fan. Crawlspace ventilation can lower indoor radon levels by reducing the homes suction on the soil, and by diluting the radon in the soil beneath the home. Passive ventilation in a crawlspace is attained by opening vents or installing additional vents. Active ventilation uses a fan to move air through the crawlspace instead of relying on natural air flow. In colder climates, for crawlspace ventilation, water pipes, sewer lines and appliances within the crawlspace may need to be insulated to protect against the cold. These ventilation technique can result in increased energy costs for the home.
An effective technique to reduce high radon levels in crawlspace homes involves covering the dirt floor of a crawl space with a high-density plastic sheet. A pipe and fan are used to draw the radon from under the sheet and exhaust it to the outdoors. This type of soil suction is called sub-membrane depressurization, and when properly applied, is the most effective method to lower radon levels in crawlspace homes. Another disfavored option is active crawlspace depressurization, which involves drawing air directly from the crawlspace using a fan.
This approach generally does not work as well as sub-membrane depressurization,and requires special attention to combustion appliance backdrafting, and sealing the crawlspace off from other portions of the home, and can also increased energy costs from the loss of conditioned air from the home.
Sealing cracks and other leaks in the foundation is a basic part to most approaches of radon reduction. Sealing the cracks helps limit the flow of radon into your home, making other radon mitigation methods more effective and cost-efficient. It also minimizes the loss of conditioned air. The USEPA does not recommend sealing cracks and leaks alone to reduce radon because, by itself, sealing has not been shown to reduce radon levels significantly, or consistently. It’s difficult to determine and permanently seal the areas where radon is entering. Normal settling of your home opens new entry points, as well as reopens old ones.
Home/room pressurization uses a fan to blow air into the basement /living area from either upstairs or outside. The concept here is to create enough pressure at the lowest level indoors for example, a basement to prevent radon from entering the home. The effectiveness of this approach is limited by home construction, climate conditions, or other appliances in the home, and the occupants lifestyle. In order to maintain sufficient pressure to keep radon out, the doors and windows in the lowest level cannot be left open, except for normal entry and exit. This technique generally results in more outdoor air being introduced into the house, which may cause moisture intrusion and higher energy costs, therefore, this approach should only be considered after the other more common method shave not sufficiently reduced radon levels.
A heat recovery ventilator(HRV), oran air-to-air heat exchanger, can be installed to increase ventilation which will help lower the radon levels in your home. An HRV will increase ventilation by bringing in outdoor air while using the conditioned heated or cooled air being exhausted to heat,or cool, the incoming air. HRVs are designed either to ventilate all or part of your home, but they are more effective for reducing elevated radon levels when they’re used to ventilate just the basement. When Properly balanced and maintained, HRVs can ensure a constant amount of ventilation throughout the year. HRVs also may improve air quality in houses that have other indoor pollutants. There could be a significant increase in the energy costs with an HRV, but not as much as ventilation without heat recovery.
Some natural ventilation exists in all homes. Opening windows, doors, and vents on the lower floors increases the ventilation in a home. This ventilation mixes outdoor air with the indoor air, diluting the radon concentration, and can result in reduced radon levels. However, once the homes windows, doors and vents are closed, radon concentrations most often return to previous levels within about 12 hours. Natural ventilation in any type of home should typically be regarded as only a temporary radon reduction technique,because of the following disadvantages: loss of conditioned air and related discomfort; increased costs of conditioning outside air; and security concerns for the home owner.
Radon in water typically is not the primary source of radon entering a home. If a radon in air mitigation system appears not to be lowering radon levels, and after several diagnostic tests, then radon in water may be evaluated as a pathway. Currently There is no guideline or recommended action level for radon concentration in water. High radon levels in water may pose an inhalation risk. This risk happens when radon is discharged into the air from water being used for showering and other household purposes. Techniques To reduce radon in water are aeration or filtration using granular activated carbon.
Source:
Epa, Us. Consumers Guide to Radon Reduction: How to Fix Your Home EPA 402/K-10/005, March 2013(n.d.): n. pag. Web.
Source URL: http://www.epa.gov/radon/pdfs/consguid.pdf
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