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Additional Combustion Safety Testing Proposed

posted Sep 25, 2012, 11:55 AM by Louis van Belle
Additional Combustion Safety Testing Options Proposed for ASHRAE Residential IAQ Standard 

ATLANTA – Additional methods to demonstrate combustion safety – an area of major concern for homes in weatherization programs – are being proposed for ASHRAE’s residential indoor air quality standard.

ANSI/ASHRAE Standard 62.2-2010, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings, defines the roles of and minimum requirements for mechanical and natural ventilation systems and the building envelope intended to provide acceptable indoor air quality in low-rise residential buildings.

Three proposed addenda to Standard 62.2-2010 currently are open for public review. For more information, visit 

Standard 62.2 currently has limits on exhaust that are based on specific assumptions about the house, specifically that the house is fairly tight. Proposed addendum w would provide professionals working in existing homes additional methods to demonstrate combustion safety, according to Paul Francisco, vice chair the Standard 62.2 committee.  This addendum allows users to consider the attributes of the actual house when assessing combustion safety to determine whether there are conditions for sufficient depressurization to cause spillage of backdrafting of a combustion appliance. This is typically an issue for atmospherically-vented appliances, usually caused by some combination of excessive exhaust, duct leakage and door closures that cause pressure imbalances.  

“Combustion safety is a major issue for weatherization programs that are using Standard 62.2,” Francisco said. “The majority of homes in those programs are leakier than the assumed leakage in the current 62.2 exhaust flow limit, even after retrofit. The current limit in 62.2 can prescriptively preclude them from using an exhaust option even though from a performance standpoint there would not be a problem.”

A secondary impact is that addendum w makes it clear that existing combustion appliances do not need to be brought up to current code as a minimum requirement of 62.2, while reinforcing that any new installations must be to code.

“The issue of bringing appliances up to code is also an issue for weatherization programs,” Francisco said. “There are many appliances installed that operate satisfactorily despite not being installed to the latest code.  With the limited budgets of retrofit programs, as well as rules in some programs prohibiting spending these limited dollars bringing existing appliances up to code unless there is a demonstrated active concern, making it clear that it is a not a mandatory requirement of 62.2 makes it easier for these programs to fully adopt 62.2 while still delivering a final result that is safe for the residents.”

One other addendum is open for public review from Sept. 14 until Oct. 14, 2012. The Standard 62.2 committee received comments from users of the standard, especially on addendum n, who did not understand which height was to be used when calculating the Normalized Leakage. Proposed addendum v would clarify the intent of the standard on how to calculate the building height.

Also open for public review from Sept. 14 until Oct. 29 is addendum u, which simplifies compliance with the intermittent ventilation requirements of Section 4.5 if the duty cycle is three hours or less. Under the current wording, designers of intermittent systems had to calculate a ventilation effectiveness factor even if operating the system 90 percent of the time with a duty cycle of one hour. This proposed addendum returns to the three hour maximum duty cycle from earlier editions of 62.2 before the ventilation effectiveness factor must be reduced below 1.0. This will simplify compliance for 80 percent of the users of 62.2. It also addresses the use of two or more fans to provide the required ventilation rate.

For more information, visit