Thinking Outside the Pit
Doug Kladder Douglas L . Kladder , Director CERTI
Active Soil Depressurization has proven to be a very reliable means by which radon laden soil gas can be reduced from indoor environments . In its simplicity , one can even say it is elegant . Core a hole , dig out a pit , connect a fan and pipe , and voila , problem solved . However , there are situationss where we may want to think “ outside the pit ” when dealing with largerr buildings , such as schools and offices where heating ventilation and air conditioning ( HVAC ) systems play a large role
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It is rare that all rooms within a school are elevated . Plotting radon readings on a floor plan helps identify areas of concern . When one is asked to explain why one portion of a building is elevated and others are not , the stock answer I typically get is “ because there must be a high radium content in the sub-grade under those rooms.” NOT ! The likelihood of large differences in subgrade make-up beneath the footprint of a building is low . Granted there can be some deep fissures that provide a unique pathway to a specific location , but that is rare and the imported fill providedd under large buildings dampens this effect . What is more likely when seeing localized areas of high radon is the effect that an imbalanced or even disabled HVAC system can have . Imbalanced HVAC systems can create tremendous negative pressures in localized areas causing radon to preferentially enter those rooms . Even to the point where an ASD system cannot overcome them . Hence , lesss than effective results .
The advice I provide students is to go back to the building and work with building maintenance personnel to understand the HVAC system . The key question you are trying to answer is : Why are thesee rooms low and the other ones highh ? Find out what is different about the low rooms and , if you are able to make the high rooms operate like the low rooms , the problem is either solved or the ASD system can function as desired . Heree are a few tips : Fresh Air Make-up Most buildings constructed in the last 50 plus years had provisions within their HVAC systems for the introduction of outdoor air when the building is occupied . This involves ductwork to the air handler , typically with a damper that is controlled by a motor thatt is controlled by an energy management system that closess the damper during off hours to reduce energy costs . This outdoor air may be provided to large central air handlers or be provided to unit ventilators serving individual rooms .