Indoor air quality and increased human exposure to air pollutants in the home and workplace has been a significant concern in recent years. Terms like "sick building syndrome" have been coined to refer to the unexplained illnesses or long term health problems people suffer as a result of exposure to indoor air contaminants. As greater efforts have been made in construction to seal out the weather, we have in effect trapped many noxious air pollutants within these structures. A common cause of poor indoor air quality is inadequate ventilation systems. This is not only a problem in the workplace, but even more so in the home as human exposure to elevated levels of Radon gas has become a serious issue. Radon is a radioactive gas generated by the natural decay of uranium found in soils. Radon gas infiltrates homes etc. through foundations, and cracks in walls posing a significant health risk as a correlation has been found between increased human exposure to Radon and an increased incidence of lung cancer. This risk has prompted research into finding cost-effective methods of protecting people from exposure to hazardous levels of Radon gas. The most common methods of reducing the accumulation of Radon gas are to keep it from entering the home (through sealing and/or ventilating foundations) or through general dilution (increased ventilation of the dwelling).
One recently developed system, the Solar Radon Reduction System (SRRS), is a low cost (home built) unit that uses forced draft, solar heated outside air that in effect pressurizes and ventilates the home. In this system Radon reduction is achieved through decreased infiltration (as a result of pressurization) and dilution (ventilation). Radon reduction rates of 24% to 29% were achieved (compared to background levels) when the system operated in the solar only mode (when the dwellings heating system was not operating) and up to 56% Radon reduction when the SRRS operated in conjunction with the home heating system. The use of the SRRS in test homes has produced small net gains in energy savings, and the entire system cost about 10% the price of commercially available systems.
The SRRS consists of a simple flat plate solar collector that can be easily built at home (for about $200.00) using many commonly land filled materials that can be salvaged from construction or demolition debris (Klein & Olson, 1993). The collector works by incorporating a corrugated metal heat exchanger (encased in a plywood backed wooden frame with a glass cover) painted black to absorb the sun's heat. At opposite corners of the collector are a fresh air inlet and a heated air discharge which is ducted into the home's main heating and ventilation system, using an electric fan. A minimum of sharp angles or elbows should be used in ducting the system as this will reduce air flow and decrease system effectiveness. Also, great care must be taken in locating the system in a place that receives maximum solar exposure and oriented facing solar south. Solar south can be easily located by placing a stick or pole in the ground and consulting the local paper for sunrise and sunset times and calculating the midway pont between them, this is solar noon. At solar noon, the shadow cast by the pole will point to true north; the opposite direction will be solar south. Complete building plans and parts list for the SRRS are available through the Recycling Reuse Technology Transfer Center.
Radon gas infiltration in the home, especially in Iowa, cannot be considered an isolated problem and the effects of increased exposure are a real concern when maximum exposure levels are exceeded (4 pCi/L). Inexpensive radon detectors are commercially available and homes should be periodically checked. In cases where radon levels above 10 picocuries per liter (pCi/L) are detected in the home, one should consider consulting a professional radon mitigator (EPA approved). The SRRS has proven effective in a variety of homes in varying locations, and is a low-cost alternative to expensive and elaborate HVAC systems under certain circumstances.
Klein, R., & Olson, J. (1993) Solar radon reduction system demonstration project.