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The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) is considering newly proposed requirements for systems that use optional demand controlled ventilation (DCV) strategies. These addenda being considered will affect current ANSI/ASHRAE Standard 62.1-2007, Ventilation for Acceptable Indoor Air Quality, which sets minimum ventilation rates and other requirements for commercial and institutional buildings, and are open for public comment until Oct. 29. They include:

• Addendum a, which clarifies air recirculation exceptions related to energy-recovery systems and allows Class 2 air to be transferred to toilet rooms;

• Addendum c, which adds performance-based requirements for each contaminant so designers in jurisdictions outside of the United States can more readily determine when air cleaning is required;

• Addendum e, which updates references to industry standards and documents;

• Addendum g, which provides additional requirements for demand controlled ventilation systems to augment the section regarding dynamic reset;

• Addendum h, which updates information regarding U.S. ambient air quality regulations; and

• Addendum i, which modifies the language in 6.2.9., Ventilation in Smoking Areas. It replaces requirements to use engineered methods to determine ventilation in ETS areas with a requirement to use increased outdoor air rates to address odor and comfort for ETS areas, but not health.

Currently, the dynamic reset section of the standard allows designers to use optional controls to reset outdoor air intake flow and/or zone minimum airflow as conditions within the system change. According to Dennis Stanke, committee chair, it would allow a ventilation-system control approach that alters outdoor air intake flow based on time of day, if variations in zone population follow a predictable schedule.

Proposed addendum 62g provides more specific requirements for such optional system controls, especially those historically called DCV and based on the use of carbon dioxide (CO2) levels, as they relate to outdoor airflow rates.

“For example, the addendum would require that optional DCV controls provide no less than the area outdoor air rate listed in Table 6-1, and that such controls maintain the minimum outdoor air intake flow no lower than the exhaust airflow rate required by Section 6.2.8,” said Stanke. “After public review and approval, this change should clarify DCV requirements.”

Addenda such as 62.1c, which would add performance-based air cleaning requirements to section 6 of the standard, would allow designers in jurisdictions outside of the United States to more readily determine when air cleaning is required. If approved, this addendum would also add air cleaning requirements for systems in non-attainment areas for particulate matter with diameter 2.5 microns (PM2.5) and smaller. Such systems would need to use intake air filters with MERV 11.

“Through better filtration, this would improve indoor air quality in many metropolitan areas of the United States,” noted Stanke.

Addendum 62.1i, which replaces mandatory language requiring that outdoor air rates for environmental tobacco smoke (ETS) areas be determined using engineered methods, operates with language indicating that increased outdoor air rates address odor and comfort for ETS areas, but not health. It also expands and clarifies a note to inform designers that increased outdoor airflow has not been shown to reduce health effects associated with ETS.

Proposed addenda to ASHRAE standards are available during public review periods. To read the addenda or to comment, visit

Publication date:10/15/2007