New requirements for demand control ventilation in single zone systems are contained in a proposed addendum to theASHRAEenergy conservation standard.

ANSI/ASHRAE/IESNA 90.1-2001, Energy Standard for Buildings Except Low-Rise Residential Buildings provides the minimum requirements for the design of energy efficient buildings. The standard is written in mandatory language and is intended for code use.

Addendum 90.1v was approved for a first public review at ASHRAE's Technology Weekend, October 3-6, 2003 in Atlanta. Public review dates will be announced later this fall.

Reducing the outside air volume when a space is not fully occupied saves energy without compromising the indoor air quality of the building, according to Carol Marriott, a member of the 90.1 committee and chair of its mechanical subcommittee.

In recent years this type of control strategy, termed demand control ventilation (DCV), has become increasingly popular and economically attractive as more manufacturers offer the components needed to implement it and equipment prices have decreased.

Proposed addendum 90.1v, which resulted from a proposal for continuous maintenance to the standard, would create new requirements for DCV in single zone systems serving spaces with high design occupant density.

"Adding the single zone requirements will ensure adequate ventilation to each space while minimizing energy required for conditioning ventilation air," Marriott said. The committee felt that since the volume of carbon dioxide sensors is increasing, and prices decreasing, DCV is economically justified for more applications.

To avoid over and under ventilation of zones, which often results when DCV is required in multizone applications, single zone DCV requirements were proposed.

Existing requirements in the standard for the application of DCV to larger, multiple-zone systems serving spaces with very high design occupant density remain unchanged.