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Simulations of Indoor Air Quality and Ventilation Impacts of Demand Controlled Ventilation in Commercial and Institutional Buildings.


pdf icon Simulations of Indoor Air Quality and Ventilation Impacts of Demand Controlled Ventilation in Commercial and Institutional Buildings. (2081 K)
Persily, A. K.; Musser, A.; Emmerich, S. J.; Taylor, A. W.

NISTIR 7042; 50 p. August 2003.

Sponsor:

Architectural Energy Corp., Boulder, CO

Available from:

Orders Only) 800-553-6847;
Website: http://www.ntis.gov

Keywords:

ventilation; commerical buildings; institutional buildings; carbon dioxide; energy efficiency; indoor air quality; volatile organic compounds; simulation

Abstract:

Carbon-dioxide (CO2) based demand controlled ventilation (DCV) offers the potential for more energy efficient building ventilation compared with constant ventilation rates based on design occupancy levels. A number of questions related to CO2-based DCV exist regarding potential energy efficiency benefits, optimal control strategies for different building types, and sensor performance and deployment. In addition, questions have been raised concerning the indoor air quality impacts, primarily with respect to contaminants with source strengths that are not dependent on the number of occupants. In order to obtain some insight into the issue of IAQ impacts of CO2-based DCV, a simulation study was performed in six commercial and institutional building spaces using the multizone airflow and IAQ model CONTAMW. These simulations compared six different ventilation strategies, with four of them using CO2 DCV, the simulations, performed for six U.S. cities, were used to compare ventilation rates, indoor CO2 levels, indoor concentrations of a generic volatile organic compound (VOC) as an indicator of non-occupant contaminant sources, and energy impacts. The results indicate that these impacts are dependent on the details of the spaces including occupancy patterns, ventilation rate requirements in the relevant standards and ventilation system operating schedule as well as the numerous assumptions used in the analysis, including contaminant source strengths and system-off infiltration rates. For the cases studied, the application of CO2 DCV resulted in significant decreases in ventilation rates and energy loads accompanied by increased indoor CO2 and VOC concentrations. The increases in CO2 were not particularly large, in the range of 180 mg/m3 (100 ppm (v)). The indoor VOC levels increased by a factor of two or three, but the absolute concentrations were still relatively low based on the assumed emission rates. The annual energy load reductions due to the use of CO2 control were significant in most of the cases, ranging from 10% to 80% depending on the space type, climate and ventilation strategy.