Study of Ventilation Measurement in an Office Building.
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.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899