ASHRAE’s new 2007 ventilation standard contains key changes impacting ventilation system designers and their designs. ANSI/ASHRAE Standard 62.1-2007, Ventilation for Acceptable Indoor Air Quality, sets minimum ventilation rates and other requirements for commercial and institutional buildings.

“Standard 62.1 has served the building industry and the public as the most prominent standard on ventilation for indoor air quality,” Dennis Stanke, committee chair, said. “Changes in the 2007 standard build on the improvements published in the 2004 version, providing additional guidance for designers of building ventilation systems.”

The new standard includes requirements for the separation of areas with environmental tobacco smoke (ETS) from areas without ETS in the same building. Although some local building and health codes prohibit smoking indoors in many buildings and locations, other codes allow smoking in designated areas. In buildings that allow smoking in designated areas, effective separation of ETS areas ensures “ETS-free” areas contain little or no ETS-related contaminants. The new separation requirements help designers ensure effective separation, according to Stanke.

Another change clarifies of how designers must analyze mechanical cooling systems to help limit space relative humidity. Many buildings suffer from air quality problems related to dampness, including mold and other microbial growth. In the past, the standard required a design analysis at specified load conditions, in an effort to demonstrate that a given design approach in a given climate could successfully limit space RH to 65 % or less.

“Those load conditions could be confusing and difficult to establish,” Stanke said. “The new requirements include a specific easy-to-establish load condition. Each system must be analyzed to check its dehumidification performance at this challenging condition to help designers make system configuration and control choices that reduce the likelihood of high-humidity problems in buildings.”

Other changes include:

• Additions to Table 6-1 of minimum outdoor air requirements for dwelling units in high-rise residential buildings. These requirements apply to residences in buildings over three stories. Low-rise residential buildings are covered by ASHRAE Standard 62.2, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings.
• New or previously overlooked occupancy categories.

  In response to proposed changes from users of the standard, ASHRAE added several occupancy categories to Table 6-1 with associated minimum outdoor air rates. These include, for example, daycare sickrooms, university/college laboratories, break rooms and coffee stations, and laundry rooms.