Analysis of Ventilation Data from the U.S. Environmental Protection Agency Building Assessment Survey and Evaluation (BASE) Study.
Analysis of Ventilation Data from the U.S. Environmental
Protection Agency Building Assessment Survey and
Evaluation (BASE) Study.
(5553 K)
Persily, A. K.; Gorfain, J.
NISTIR 7145-Revised; 122 p. November 2008.
Sponsor:
Environmental Protection Agency, Washington, DC
Keywords:
ventilation; surveys; evaluation; carbon dioxide; office
buildings; air intake; systems engineering; maintenance;
occupants; air flow; diffusers; air quality; ventilation
systems; ASHRAE 62-2007
Abstract:
[Replaces Version (NISTIR 7145) Published in December
2004] The U.S. Environmental Protection Agency (EPA)
Building Assessment Survey and Evaluation (BASE) study
included a range of measurements in 100 randomly
selected U.S. office buildings for the purpose of
characterizing the existing building stock with respect
to determinants of indoor air quality and occupant
perceptions of indoor environments. One aspect of the
evaluation was the characterization of the ventilation
systems serving the study spaces and selected
measurements of ventilation performance. This report
presents an analysis of these data with a focus on
supply and outdoor airflows, including comparisons of
the measured data with design values and the outdoor air
requirements in ASHRAE Standard 62-2001. The results
indicate that, as expected based on thermal load
considerations, the average value of the design and
measured supply airflow are both about 5 L/sDT-m2 (1
cfm/ft2). The measured outdoor air ventilation is higher
than might be expected, with a mean value of 49 L/s (105
cfm) per person based on volumetric airflow measurements
at the air handlers and measured occupant densities.
These outdoor air ventilation values are high on average
relative to the minimum outdoor air requirements in
Standard 62 due to the high outdoor air fractions
(relative to minimum) and the actual occupancy being on
average 80% of the design occupancy. Nevertheless, about
17% of the ventilation measurements are still below the
10 L/s (20 cfm) per person requirement in Standard 62.
Under conditions of minimum outdoor air intake and
accounting for the lower occupancy levels, the mean
ventilation rate is roughly 11 L/s (22 cfm) per person
and about onehalf of the values are below the per person
requirement in Standard 62. In addition, this report
contains a number of suggested modifications to the
protocol used in these assessments for consideration in
future studies. This report is a revision of the
original report on these data published in 2004. This
revision reflects some additional analyses of the data,
which results in some changes to the numerical values
reported, but not to the overall conclusions. The
additional analyses are discussed in Appendix F of this
report, which was published as a NIST Letter Report in
October 2008. All values in this revised report that
have changed relative to the original report are noted
in bold font. Those tables and figures have been updated
are also noted in bold font in the lists of tables and
figures page vii and viii respectively.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899