ANSI Upholds Ventilation Rate Procedure
The standard, "Ventilation for Acceptable Indoor Air Quality," sets minimum ventilation rates and other requirements for commercial and institutional buildings. The ANSI denial upholds Addendum 62n, which revises the procedure used to determine design ventilation rates. "The procedure now is more straightforward, allowing designers to determine rates and reduce the potential for overventilation in some densely occupied spaces," according to David Butler, P.E., committee chair. Furthermore, he said, the standard is now focused on minimum requirements. The addendum was approved for publication at the society's 2003 annual meeting. Six appeals were filed and later denied by ASHRAE. On May 20, the ANSI Board of Standards Review announced that it voted to deny all appeals made to that organization, thereby upholding its earlier approval of the addendum.
"Because air pollutants are generated by building occupant activities and by building contents, the addendum bases ventilation requirements on the number of people a space is expected to hold, as well as the space's floor area," Butler said. The "additivity" procedure calculates minimum outdoor ventilation requirements for a ventilation system. For example, in an office building the procedure determines the amount of outdoor air needed for each space type (i.e., offices, conference rooms, corridors); this in turn is used to determine the amount of outdoor air intake required at the air handler.
In comparison, "The existing procedure, issued in 1989, contains a number of requirements that are difficult for designers to comply with and that do not allow designers to explicitly account for occupant density in a space," Butler said.
A spreadsheet helps make the calculation methods easier for users to apply; 62n.VRP.xls is available under the SSPC62.1 directory at ftp.ashrae.org. Addendum 62n can be downloaded at no cost via the "standards addenda index" shortcut on www.ashrae.org.
Publication date: 07/12/2004