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.
(3103 K)
Persily, A. K.; Gorfain, J.
NISTIR 7145; 101 p. December 2004.
Keywords:
carbon dioxide; design; measurement; mechanical
ventilation; office buildings; ventilation
Abstract:
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/sBLm2 (1 cfm/ft2). The measured outdoor air
ventilation is higher than might be expected, with a
mean value of 55 L/s (117 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.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899