BRINGING RADON BACK ON THE RADAR

Transcription

1 BY GORD COOKE BRINGING RADON BACK ON THE RADAR In the indoor air quality (IAQ) business the current pressing concern seems to be mould. Mould and moisture issues dominate articles in industry journals and mainstream media therefore contractors and consumers tend to fixate on mould as the potential root of indoor air quality problems. However, if we stepped back in time 15 to 20 years the dominant issue would have been radon. It was in 1984 in Pennsylvania that the issue of radon gas in houses became widely publicized. The issue was triggered by a curious situation where an engineer at a nuclear plant kept setting off the radiation alarm when he passed monitoring checkpoints. This was very odd since there was not any radioactive fuel in the reactor at the time. It was discovered that he was carrying dangerous radiation levels with him from home. Investigation revealed that his house had extremely high levels of radon gas It is these progeny that become lodged in the lungs and, upon further decay, emit small bursts of radiation to lung tissue. With long-term exposure these radiation bursts can result in lung cancer. seeping from exposed soils and rock in the basement. Radon is an ongoing concern in houses and other buildings. There is still considerable research, remediation work and, on occasion, public awareness events regarding the radon issue. MIGRATION PATTERNS Radon gas is a naturally occurring gas that seeps up from the earth as part of the radioactive decay of uranium. While uranium and radon occur in trace amounts in all soils and rocks, granite and shale typically have higher concentrations. In addition, certain types of soils transmit radon gas more easily than others. As a result, radon concentrations and patterns of migration are highly variable and, although there are known radon hot spots, it is very difficult to predict, at a local level, which houses may have high radon concentrations. Radon gas can accumulate inside enclosed spaces, such as basements, as it seeps through cracks and penetrations in foundation walls and slabs. The fact that basements are often under negative pressure due to stack effect (warm air rising in houses) and mechanical effects with chimneys and loose return air ducts CONTINUED ON PAGE 20 Photo Hemera Technologies Inc. 18 HPAC SEPTEMBER/OCTOBER 2005 Circle #11

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3 CONTINUED FROM PAGE 18 drawing air from the basement, increases radon concentrations in basements. HEALTH RISKS It is useful to understand that the health risk from radon is not associated with the radon gas directly. The half-life of radon is very short. Within a matter of days the gas decays into other elements referred to as radon progeny. These elements have a small static charge that allows attachment to water vapour, dust, smoke and other small particles floating in the air. It is these progeny that become lodged in the lungs and, upon further decay, emit small bursts of radiation to lung tissue. With long-term exposure these radiation bursts can result in lung cancer. The effect is always due to longterm exposure. Radon gas is odourless, colourless and tasteless and there are no known short-term symptoms or signs of radon gas exposure. There is on-going debate as to the extent of the risk as it relates to the concentration of radon gas in an individual home. For example, radon gas is measured as the number of picocuries/litre of air (a picocurie is one-trillionth of a Curie). In ambient air typical levels would be 0.4 pci/l. The U.S. Environmental Protection Agency (EPA) has set the recommended maximum radon level at four pci/l, while a level of 20 pci/l is the action level in Canada. There is no doubt that exposure to radon and its decay products increase the risk of lung cancer. The World Health Organization (WHO) concluded that radon is responsible for about 10 per cent of all lung cancers. 20 HPAC SEPTEMBER/OCTOBER 2005 Circle #13 LONG-TERM TESTING There are many radon testing firms in the U.S., and a few in Canada, who can measure radon levels in individual houses. There are at least four different measuring techniques used, ranging from a 24-hour to one-year long monitoring base. Given that radon is a longterm issue and radon levels can vary considerably from day to day, long-term testing is preferred. All legitimate testing requires laboratory analysis and consumers should be aware of do-it-youself test kits. That said it is possible to order monitoring equipment, install it yourself and then send it off to an accredited lab for analysis. The best source for information on radon testing is the EPA ( Fortunately the extensive testing throughout the U.S. has lead to an understanding of the most effective ways to eliminate radon gas concerns in existing homes and avoid concerns in new houses. You will recall from other IAQ articles that the strategies for IAQ improvement are remove, seal, ventilate and then filter (in that order). Recognizing that it is impractical to remove the source since radon gas is naturally occurring in all soils, the prime strategy in radon control is to

4 seal or isolate, combined with modified ventilation strategies. CONTROL STRATEGIES Here are recommended radon control strategies for new and existing houses. You will note that HVAC contractors can be part of the solution. Seal all cracks and penetrations in the foundation. Depressurize underneath the foundation slab. Reduce negative pressures in basements. Properly ventilate the house. As shown in Figure 1, the first step is to seal all cracks and penetrations in the foundation slab and walls. This would obviously include covering dirt floors with heavy polyethylene sheets and sealing them at all seams and edges. In houses with concrete slabs this would include caulking around plumbing penetrations and at slab edges. Floor cracks must be properly grouted. In new construction the building code recommends having a continuous sealed polyethylene sheet under the entire concrete slab. This practice has become common in many areas. Most importantly, a sealed sump pit cover should be installed whenever a sump pit is within the heated envelope of the house. In new houses there are sump pit kits available with a sealed cover and gasketing system for pipe and wire penetrations. In existing houses a cover can be fashioned from plastic or metal sheet or even coated plywood with gaskets used to seal penetrations. PATHWAY FOR GASES Concrete block foundations are often a special case. The hollow core block is a pathway for radon gas, moisture and other ground soil gases. In new construction the bottom course and top course of block should be filled with mortar of foam. In existing houses the top course of block can often be filled with foam under the top plate. Once the foundation is sealed the strategy most often used to control radon is to depressurize the underside of the slab. This is accomplished by installing a four- to six-inch diameter PVC pipe down through the basement slab and into the aggregate below. The pipe is then run up through the house and out through the roof. An inline fan is installed either on the top of the PVC pipe or within the pipe (mounted in the attic to ensure the entire pipe stays under negative pressure). The effectiveness of this system is dependent on the permeability of the soil under the slab. Building code requirements of four- to six-inches of stone under slabs are meant to allow for sub-slab depressurization in the event of future soil gas or radon concerns. Simply roughing-in the pipe and allowing it to work as a passive depressurization system (avoiding the need for the fan) can be a first step. Some basements may need more than one exhaust fan to create the small negative pressure required across the entire slab. Other options would include installing an exhaust vent pipe (like the one described above) from a sump pit. For those who are interested, the EPA has full design and installation model standards FIGURE 1 Radon control for existing houses: sub-slab depressurization seal cracks and openings to soil depressurized zone FAN that thoroughly describe a sub-slab depressurization system for houses and large buildings. There has also been research on pressurizing under the slab and it has been shown to be very effective as well. That said, depressurization has been the most common remedial measure. CONTINUED ON PAGE 22 Get Into Duct Cleaning With The Best. Abatement Technologies Equipment and Accessories Are The Overwhelming Choice of Duct Cleaning Pros Worldwide. Our Products Are Known For Their Quality, Performance, Reliability And Durability. Get All The Info You Need To Make A Smart Business Decision! Call Today Packages $7,495! cdn , Abatement Technologies, Ltd., Fort Erie, ONT All Rights Reserved. SEPTEMBER/OCTOBER 2005 HPAC 21

5 CONTINUED FROM PAGE 21 NEGATIVE PRESSURE It is known that the normal stack effect in houses in winter induces a negative pressure on basements. In addition, the return air ducts of furnaces and the air required for combustion and venting of chimney-connected appliances also contributes to the negative pressure in basements. To reduce the entry of radon into basements the following measures would be very helpful: air seal all return ducts and plenums in basements; eliminate chimneys and the need for combustion air from inside by using direct vent combustion appliances that take combustion air from outside; and air seal penetrations near the top of homes (ceiling light fixtures, plumbing penetrations, chimney chases etc) to reduce the amount of air that leaves the house due to stack effect which reduces the negative pressure in basements. These measures are much easier to implement in new houses. By making houses tighter, specifically the top of houses, and by installing high efficiency, direct vent appliances, air quality is improved. There are many synergistic benefits between air quality and energyefficient strategies. New Coleman HVAC Systems: Put your sales into higher gear The new Coleman Echelon TM Series. Finally, a family of products that offer comfort, aesthetics and differentiation while giving you the kind of profitability you ve always imagined. This is the complete outfit: style, efficiency, rugged reliability plus it s environmentally friendly. It includes a full range of mid and high efficiency Gas Furnaces as well as Air Conditioners and Heat Pumps (including 410A models) up to 15+ SEER and as low as 6.9 db sound levels. For a closer look at our HVAC gear and information on the Coleman Liberties Dealer Program, call us at ROLE OF VENTILATION The last radon measure, but one that should be of interest to HVAC contractors, is proper ventilation. While ventilation is not the most effective measure for controlling radon, it is useful to know that continuous mechanical ventilation can also be justified as a radon measure. That is, codes and standards have required mechanical ventilation in all houses for at least 15 years. It should be comforting to your customers who have heard or read the latest about the dangers of radon, that you have already addressed their concerns by installing (or at least quoting on) a properly installed, balanced ventilation system. While radon may not be the most publicized air quality issue at the moment, it is an ongoing concern. As with most IAQ issues, HVAC contractors are an important part of remediation measures and need to be aware of the issues and opportunities. They can help prevent radon concerns by offering premium products and services balanced whole house ventilation, direct vent combustion appliances and air sealed duct work. Gord Cooke, P.Eng., is president of Air Solutions Inc., Cambridge, ON. Contact him at , gcooke@airsolutions.on.ca or visit for more information. The Echelon 3S, 5T and 9S/T/V models meet Energy Star requirements for energy efficiency. The Indoor Outfitters OAKVILLE, ON., CANADA Coleman and the Coleman logo are registered trademarks of The Coleman Company, Inc., used under license. Manufactured by Unitary Products Group, Inc., 5005 York Drive, Norman, OK The Coleman Company, Inc. RATE THE ARTICLE! Will this information be useful? Please circle the appropriate number on the Reader Postcard. Thank you. VERY USEFUL USEFUL NOT USEFUL HPAC SEPTEMBER/OCTOBER 2005 Circle #14