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Study of Ventilation Measurement in an Office Building.


pdf icon Study of Ventilation Measurement in an Office Building. (1538 K)
Dols, W. S.; Persily, A. K.

NISTIR 4905; 42 p. October 1992.

American Society for Testing and Materials. Airflow Performance of Building Envelopes, Components, and Systems. ASTM STP 1255. 1995, Philadelphia, PA, ASTM, West Conshocken, PA, Modera, M. P.; Persily, A. K., Editor(s)(s), 23-46 pp, 1992.

Sponsor:

Bonneville Power Admin., Portland, OR

Available from:

National Technical Information Service (NTIS), Technology Administration, U.S. Department of Commerce, Springfield, VA 22161.
Telephone: 1-800-553-6847 or 703-605-6000;
Fax: 703-605-6900.
Website: http://www.ntis.gov
Order number: PB93-113595

Keywords:

office buildings; air flow; building performance; carbon dioxide; commercial buildings; indoor air quality; measurements; tracer gas; ventilation; pitot tube; hot wire anemometers

Abstract:

The National Institute of Standards and Technology has conducted a study of ventilation and ventilation measurement techniques in the Bonneville Power Administration (BPA) Building in Portland, Oregon. The project involved the comparison of outdoor air ventilation measurement techniques for relative accuracies and an examination of changes in building ventilation rates over time. The following measurement techniques were compared: tracer gas decay measurements of whole building air change rates, the determination of air change rates based on peak carbon dioxide (CO2) concentrations, the determination of percent outdoor air intake using tracer gas (sulfur hexafluoride and occupant-generated CO2), and direct airflow rate measurements within the air handling system. In addition, air change rate measurements made with an automated tracer gas decay system approximately three years apart were compared. The major findings of the study are as follows. Airflow rates were measured in the air handling system ductwork using pitot tube, hot-wire anemometer, and vane anemometer traverses, and good agreement was obtained between the different techniques. While accurate determinations of percent outdoor air intake were achieved using tracer gas techniques, the use of CO2 detector tubes yielded unreliable results. Reliable determinations of ventilation rates per person were made based on SF6 decay and direct airflow rate measurements but the use of peak CO2 concentrations led to inaccuracies, i.e., the overprediction of ventilation rates by as much as 100%. The measured values of the whole building air change rates, and their dependence on outdoor air temperature, did not change significantly over a three year period. The minimum air change rates were above the building design value and ASHRAE Standard 62-1981, the standard on which the design was based, but the minimum rates were below the minimum recommendation given in Standard 62-1989. The whole building air change rate under minimum outdoor air intake conditions was determined to be twice the outdoor air intake rate provided by the minimum outdoor air intake fans. The additional air change under minimum outdoor air intake conditions was due primarily to leakage through the main outdoor air intake dampers.