January 30, 2002—Requirements to ensure that air distribution systems are capable of delivering outdoor air to occupied spaces are contained in the American Society of Heating, Refrigerating and Air-Conditioning Engineers’ (ASHRAE) ventilation standard in an addendum newly approved for publication.
ANSI/ASHRAE Standard 62-2001, Ventilation for Acceptable Indoor Air Quality, sets minimum ventilation rates and other requirements for commercial and institutional buildings.
Five addenda to the standard were approved for publication at the Society’s 2002 Winter Meeting.
Addendum 62v addresses balancing, plenum mixing systems, exhaust duct location and documentation. In systems with air-conditioning units, heat pumps or fan-coil units mounted in a ceiling or floor plenum, ventilation air is often supplied to the plenum to mix with recirculated air, according to Andrew Persily, chair of the Standard 62 committee.
If outdoor air is poorly distributed in such systems, units that are far from the outdoor air supply to the plenum may not receive the intended levels of outdoor air. In any air distribution system, required airflow can only be assured by measuring actual airflow and adjusting dampers and orifices to account for the effect of as-installed duct pressure drops.
Another addendum, 62i, provides guidance on when to use the indoor air quality procedure, describing situations in which the IAQ procedure can or must be used, and does so in mandatory and enforceable language.
The ventilation rate procedure is a prescriptive approach in which outdoor air intake rates are determined based on space type/application, occupancy level and floor area.
Other addenda approved for publication are:
- 62t clarifies requirements related to condensate management, including drain pan design, carryover from cooling coils and access for inspection and cleaning.
- 62u relates to the control of ventilation systems, specifically controls to ensure adequate ventilation whenever buildings are occupied and under any thermal load conditions.
- 62ab addresses equipment that generates contaminants and the need to duct such equipment with integrated exhaust ventilation to the outdoors.
For more information about ASHRAE standards, contact ASHRAE Online.
