How can you reduce radon in a home?

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Susanna Hunter
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1 Lesson 10: How can you reduce radon in a home? Lesson overview This lesson provides a brief overview of radon mitigation. Lesson objectives By the end of this lesson, the learners will be able to: Describe most common methods for reducing radon in the air Recognize major components of sub slab depressurization systems Describe the two methods of reducing radon in tap water As you know, this course covers how to measure radon. It is not a course in radon mitigation, or the ways of reducing radon in the air or in tap water. However, if the radon levels in your clients homes are too high, you may need to know something about reducing radon and radon reduction systems so that you can answer basic questions from your clients before you refer them to trained radon mitigation specialists. The most important message for clients is that if high levels of radon are found in the home, they can be reduced. To decrease airborne radon levels to below 4.0 pci/l, a homeowner should hire a qualified radon professional. See slide As we ve said, mitigation is the reduction of radon in air or water. In Connecticut, mitigation should be performed only by a home improvement contractor who Is registered with the Connecticut Department of Consumer Protection Has successfully completed radon mitigation training Is listed as a residential mitigation service provider with the National Radon Safety Board (NRSB) or the National Environmental Health Association (NEHA) See slide 10 2 You can refer your clients to the Connecticut Department of Public Health s website at Lesson 10 1

2 for a listing of mitigation contractors who meet these requirements. See slide There are two basic ways that radon can be reduced in homes: 1. Depressurization: a home s pressure is reduced so that radon gas does not enter the home. Instead, radon is drawn into piping and exhausted at the roofline. 2. Pressurization: air is blown into a space and the radon gas is diluted or blown out of the space. Both methods involve sealing foundation openings. See slide The Environmental Protection Agency usually recommends radon mitigation methods that prevent radon from entering a home (depressurization methods) rather than those that simply reduce the amount of radon already present. The focus of this section is on most common type of radon mitigation system: a subslab suction or subslab depressurization system. See slide The most effective methods are usually designed to suit a home s construction, especially its foundation design and materials. We ll talk about them in a few minutes. In homes with different foundations (that is, basement, slab ongrade, or crawlspace), several radon mitigation methods may be necessary. A qualified contractor will conduct a visual inspection and diagnostic testing to determine the most effective mitigation system for a property. See slide In a home with a basement or a slab on grade foundation, radon is usually reduced by soil suction. Most homes in Connecticut have basements or slab on grade foundations. Therefore, soil suction is the most common method. Suction prevents radon from entering the home by Lesson 10 2

3 Drawing radon from below the home Venting radon to a pipe or pipes Releasing radon into the air above the home We ll explain this type of system in greater detail so that you are familiar with the its components and basic requirements for proper installation. See slide Active subslab suction (also known as subslab depressurization, or SSD) is the most common and usually the most reliable method to reduce radon. It is also the most common system found in CT. A mitigation contractor inserts suction pipes through the slab into the soil or crushed rock below. The contractor may also insert pipes below the slab from outside the home. A vent fan connected to the pipes creates a vacuum (negative pressure) under the slab. It draws radon gas from below the home and releases it outside, above the roof eave. Subslab suction works best when air can move easily in the material under the slab. See slides 10 8 through We ll give an overview of the requirements for an SSD system. As a home inspector, you should be familiar with these systems: what they look like, and what is expected in a standard installation. The following are the major requirements of an SSD system: 1. All components of the radon mitigation system should be clearly labeled, Radon Reduction System. This labeling will allow for maintenance and repair and will prevent disruption of the system during renovation. 2. If the system has an exhaust fan, the fan must be located outside and above the habitable space of the building. a. It may be located outside or in an unoccupied attic. b. It may not be located in a basement. 3. Any exhaust fan must be located in a vertical run of the vent pipe. 4. If there is an exhaust fan, there should be a visible or audible warning device to alert occupants if the system fan stops Lesson 10 3

4 working. 5. The vent pipe must end at least 12 inches above the surface of the roof and less than 2 feet below the exhaust fan. 6. The vent pipe must end at least 10 feet from any window or opening into the house and at least 10 feet from any adjoining or adjacent buildings 7. In some mitigation systems, the radon vent pipes run along the outside of the building. In these systems, ties or brackets must secure the vent pipes: a. Every 6 feet in a horizontal run of pipe b. Every 8 feet in a vertical run of pipe. We will now review the major components of a subslab depressurization system. The following slides will show you what a typical SSD system installation looks inside and outside a home. See slide Radon mitigation contractors are required to label the systems that they install. A properly installed system should be labeled a radon reduction system. Stickers, sold by major manufacturers, are simply stuck to the piping. Also, radon mitigation contractors must attach contact information to the systems that they install. If a client has questions on the operation or installation of a system, you can refer them to the contractor s documentation and the contact information included with the SSD system. See slide Exhaust fans can be located in two places in homes: On the exterior In an unoccupiable space in the attic This slide shows a picture of an exhaust fan installed on the exterior of a home. Note that the fan is installed vertically and that the wiring is located on the outside of the building. This is not the only type of fan unit for SSD systems. Some fans look like boxes that are mounted flush to walls. Lesson 10 4

5 See slide A more effective installation method for an SSD system is installed the piping and fan on the interior of the home. When a fan is installed on the interior of the home, it must be located in an unoccupiable space in the attic. A fan may not be installed in a basement. See slide This slide shows a manometer, which acts as a visible warning device that alerts residents if the fan stops working. Most residential systems have a manometer. (Schools and commercial buildings have alarms.) The manometer does not measure radon in a home. The liquid inside the U shaped tube shows the pressure difference between the interior and subslab air pressure. The difference in liquid levels on each side of the U shaped tube indicates that the system fan is operating. When a fan burns out or stops working, the liquid levels on each side of the U shaped tube will be equal. That means that the system is not working and needs to be repaired. See slide You also need to recognize the vent stack pipe. It carries radon away from the home and exhausts gases so that they do not re enter the home. When installed on the exterior of a home, the piping must extend at least 10 feet above ground level. When practical, it should extend to the highest roof of the building and above the highest ridge. The discharge point must be at least 12 above the roofline or eave (to ensure that snow does not cover it during the winter months). The discharge point must be vertical. That means that should not be an elbow or other turn in the pipe where it ends. The discharge point must also be at least 10 feet from windows, doors, or other openings into occupiable space, if the discharge point is not at least 2 feet above the top of such openings. See slide Lesson 10 5

6 The discharge point on a interior installation is slightly different. There will be a roof penetration with a labeled radon system pipe coming out of it. As with an exterior application, all requirements for the stack vent pipe and its discharge point apply. If, during a home inspection, you find a system that does not meet these requirements, you should refer your client to a radon mitigation contractor to correct the issues. See slide Several other methods that can be used to depressurize a home, although we will not discuss them in detail. The basis for their operation and their components are similar to those of the SSD systems. Air that contains radon is drawn from within a building component (for example, a block wall) into a pipe and is then exhausted to the exterior. The differences between the systems stem from how the home is being depressurized (suctioned). The depressurization method is based on the home s construction. Suction points may be through a drain tile, sump hole, block wall, membrane. or sealed crawlspace. See slide As mentioned earlier, radon mitigation systems may also pressurize a space. Reducing radon through pressurization dilutes the radon gas in a home and blows the radon out of the home. These methods are less common than depressurization methods. They are often used in homes with dirt or stone basements, where depressurization is not possible. Typically, home/room pressurization or heat recovery ventilators are used when depressurization methods would be ineffective. See slide Consider. Do you have any questions on reducing radon in air in homes? See slide So far in this lesson, we ve been talking so far about reducing radon in the air. But we ve noted that homes may also have high levels of radon in the water. Lesson 10 6

7 Radon in water can be treated in two ways: Point of entry systems, which remove radon before the water is distributed o These systems treat all the water in the home o There are two types of point of entry systems: Granular activated carbon (GAC) Aeration Point of use systems, which remove radon from water at the tap o These systems treat only a small percentage of household water o They are ineffective in treating radon in water and reducing the overall burden of radon in a home We ll focus on point of entry systems. See slide The granular activated carbon (GAC) system is used to treat radon in water levels from 5,000 pci/l to below 10,000 pci/l It is less expensive than the aeration system. A GAC system filters water through a carbon bed, which traps radon and radon decay products. The tank may emit some radiation and may require shielding. The filter must be changed each year and requires careful disposal. See slide An aeration system is used to treat radon levels 10,000 pci/l and above. It is more expensive than a GAC system. An aeration system mixes water with air and vents radon outdoors. The system does not become radioactive but does require a yearly cleaning. See slide In this lesson, we offered a brief overview of ways of reducing high levels of radon in air and in water. We noted that mitigation should be done by a qualified mitigation contractor. It involves A visual inspection Consideration of the home s construction Lesson 10 7

8 Diagnostic testing We described two general methods of mitigation for radon in the air: Depressurization systems Pressurization systems We also discussed the most common type of system for reducing radon in air a subslab depressurization system. See slide We also mentioned that there are various mitigation methods that can be used on various types of foundations. Good diagnostics and evaluation of a home, will allow a mitigation contractor to select the most appropriate system. In general, for slab on grade and basement foundations, contractors may use Subslab suction Drain tile suction Sump hole suction Block wall suction For crawlspace foundations, contractors may use Submembrane suction Active depressurization Crawlspace ventilation For homes with dirt foundations, contactors typically use Heat recovery ventilators House/room pressurization See EPA s Consumer s Guide to Radon Reduction: How to Fix Your Home (EPA 402 K , revised February 2003, and available at The information in this lesson is mainly drawn from the EPA publication, a Consumer s Guide to Radon Reduction: How to fix your home (EPA, 2003). You can download an electronic version from the EPA website and give a copy to your clients. Check comprehension. See Handout 10 2A. This comprehension check is not graded. Lesson 10 8

9 Now you re going to see whether you remember the main points that we ve discussed in this lesson. Please answer the questions on handout 10 1A. When you are all finished, we ll review the answers together. See Handout 10 1B, the answer key. Review the answers. Lesson 10 9

10 Resources Iowa State University, College of Engineering, Agricultural and Biosystems Engineering Radon Reduction Methods: A Homeowners Guide. Accessed July 17, U.S. Environmental Protection Agency. Office of Air and Radiation, Office of Radiation and Indoor Air (6609J) Consumer s Guide to Radon Reduction: How to Fix Your Home. EPA 402 K February. Lesson 10 10

11 Handout 10 1A: Check your understanding Select the best answer from the choices below. Circle the correct answer. 1. The Environmental Protection Agency recommends mitigation methods that a. Prevent radon from entering a neighborhood b. Prevent radon from entering a home c. Remove radon at the lowest living level d. Remove radon at any point where it reaches 4 pci/l 2. Mitigation contractors will prior to installing a system a. Identify potential radon entry paths b. Identify relevant construction features c. Conduct diagnostic tests d. Consult state radon distribution maps 3. Which of the following methods is usually the most effective in a home with a slab on grade foundation a. Natural ventilation b. Active subslab suction c. Passive subslab suction d. Sealing foundation openings 4. Sealing foundation openings a. Must be used in combination with other methods to be effective b. Is the single best method to reduce radon in basements c. Is easy for a qualified contractor to complete d. Is usually a permanent solution to radon entry 5. After testing the tap water in a home, you receive the results: an average of 8,540 pci/l. You refer the client to a mitigation contractor. Which type of system is probably best to reduce the radon levels in water in this home? a. Active subslab suction b. Aeration c. Granular activated carbon d. Submembrane suction Lesson 10 11

12 Handout 10 1B: Check your understanding Answer key The correct answers are shown in bold. 1. The Environmental Protection Agency recommends mitigation methods that a. Prevent radon from entering a neighborhood b. Prevent radon from entering a home c. Remove radon at the lowest living level d. Remove radon at any point where it reaches 4 pci/l 2. Mitigation contractors will not prior to installing a system, except for a. Identify potential radon entry paths b. Identify relevant construction features c. Conduct diagnostic tests d. Consult state radon potential maps 3. Which of the following methods is usually the most effective in a home with a slab on grade foundation a. Natural ventilation b. Active subslab suction c. Passive subslab suction d. Sealing foundation openings 4. Sealing foundation openings as a means to reduce radon a. Must be used in combination with other methods to be effective b. Is the single best method to reduce radon in basements c. Is easy for a qualified contractor to complete d. Is usually a permanent solution to radon entry 5. After testing the tap water in a home, you receive the results: an average of 8,540 pci/l. You refer the client to a mitigation contractor. Which type of system is acceptable for radon levels in water in this home? a. Active subslab suction b. Aeration c. Granular activated carbon d. Submembrane suction Lesson 10 12

Connecticut Radon Measurement Training Program

Connecticut Radon Measurement Training Program Lesson 10 How can you reduce radon in a home? Brief overview of radon mitigation Mitigation: reducing radon in air or water Requires trained, registered radon mitigation specialist Typical radon mitigation