Public Input Sought on Alternative to ASHRAE Standard 62.1 Ventilation Rate Procedure Proposed ATLANTA – A proposed change to the ventilation rate procedure in ASHRAE’s indoor air quality standard is open for review after changes were made based on public input last year. ANSI/ASHRAE Standard 62.1-2010, Ventilation for Acceptable Indoor Air Quality, sets minimum ventilation rates and other requirements for commercial and institutional buildings. The ventilation rate procedure provides a prescriptive method for determining minimum ventilation requirements. It accounts for pollutant sources from both the building and its occupants, and allows the designer to account for the efficiency of different ventilation systems when delivering outdoor air to the breathing zone. Proposed addendum f was first released for public comment in September 2011 after some users of Standard 62.1 indicated the ventilation rate procedure was “too complicated,” according to Standard 62.1 chair Roger Hedrick. He said the 62.1 committee agreed that application of the multiple-zone recirculating system equations described in Section 6.2.5 and Appendix A can be complex. “When designing multiple zone recirculating ventilation systems, Table 6-3 provides a default value of Ventilation Efficiency (Ev) based on the largest value of the zone primary (Zp) outdoor air fraction, for all the zones served by the system,” he said. “However, if Max (Zp) exceeds 0.55, then Appendix A must be used to design the system outdoor airflow. Addendum f attempts to simplify the design process by providing a simplified default approach for cases with Max (Zp) greater than 0.55.” The earlier review draft set the default value of the zone primary outdoor air fraction based on a default minimum zone primary airflow set as 30 percent of the zone design primary airflow. “The public review comments pointed out that this formulation did not work mathematically under certain conditions,” Hedrick said. “This new public review version instead simply allows Ev to be set to 0.6, unless a higher value is provided by Table 6-3 or by using Appendix A. Use of a relatively low value of Ev will result in higher outdoor airflow rates, but using the default will simplify the system design process.” Also open for review is addendum i, which would add limits for low humidity. Recent studies have shown that excessively low humidity may result in unacceptable indoor air quality. The Standard 62.1 committee is interested in the appropriateness of the relative humidity limit and the climate zones where the requirement applies. The addendum is open for an advisory public review, meaning comments received allow for constructive input and need not be resolved or formally acted on by the project committee. In addition to addenda f and i, three additional addenda are open for public review from March 23 until April 22. For more information, visit www.ashrae.org/publicreviews. They are:
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