Ashrae Journal - December 2008 - (Page 18) Criteria for Outdoor Air Monitoring By Thomas M. Lawrence, Ph.D., P Member ASHRAE .E., T CO tion for Acceptable Indoor Air Quality, but does not list what the actual CO2 concentrations are. LEED-NC, version 2.2, (new construction) offers a credit (EQ Credit 1) for monitoring of CO 2 concentrations in mechanically ventilated densely occupied (≥25 people per 1,000 ft² [100 m2]) spaces, and in all naturally ventilated spaces. Again, no specific maximum CO2 concentrations are ashrae.org ASHRAE Journal O 2 Selecting he operation of buildings is as, or is more important than, the original design in maintaining a healthy indoor environment and energy efficiency. A number of certification programs and standards specify the use of ventilation system performance monitoring. Monitoring is to be done either based on CO2 concentrations in the occupied space or actual measurement of outdoor airflow, depending on the space design occupancy and ventilation type (mechanical or natural). For example, outdoor air delivery monitoring is a credit option for new construction, existing buildings and the core and shell LEED® programs from the U.S. Green Building Council. The current standards or program descriptions do not provide detailed guidance for determining what concentration of CO2 should be considered the maximum concentration. The LEED-EB (for existing buildings) credit mentions CO2 concentrations 15% above that expected to occur with a corresponding minimum outdoor airflow rate required by ANSI/ ASHRAE Standard 62.1-2007, Ventila18 CO About the Author Thomas M. Lawrence, Ph.D., P .E., is a public service associate with the Faculty of Engineering at the University of Georgia in Athens, Ga. provided. The California Title 24 2008 Building Energy Efficiency Standards specifies a maximum CO2 concentration of 600 ppm above ambient as a “one size fits all” criteria for spaces using demand ventilation controls. However, this only applies to California because it has its own ventilation standard, which is not based on Standard 62.1. Decisions must be made regarding the balance between having adequate outdoor air ventilation to the occupied space while still considering the energy requirements needed to condition that ventilation air. Section 6.4.3.8 in ANSI/ ASHRAE/IESNA Standard 90.1-2007, Energy Standard for Buildings Except Low-Rise Residential Buildings, describes the allowances for dynamic reset of outdoor air ventilation for densely occupied spaces. ASHRAE Journal has published many articles during the past decade that deal with outdoor airflow control (demand-controlled ventilation 2 December 2008 http://www.ashrae.org
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