Indoor Air Quality Impacts of Residential HVAC Systems. Phase II.B Report: IAQ Control Retrofit Simulations and Analysis.
Indoor Air Quality Impacts of Residential HVAC Systems.
Phase II.B Report: IAQ Control Retrofit Simulations and
Analysis.
(7219 K)
Emmerich, S. J.; Persily, A. K.
NISTIR 5712; 89 p. September 1995.
Sponsor:
Consumer Product Safety Commission, Washington, DC
Available from:
National Technical Information Service
Order number: PB96-106877
Keywords:
indoor air quality; heating; ventilation; air
conditioning; air change rates; air flow modeling;
building technology; computer simulation; filtration;
heat recovery ventilation; infiltration; modeling;
outdoor air; residential buildings
Abstract:
The National Institute of Standards and Technology
(NIST) performed a preliminary study of the potential
for using central forced-air heating and cooling system
modifications to control indoor air quality (IAQ) in
residential buildings. The objective of this effort was
to provide insight into the use of state-of-the-art IAQ
models to evaluate such modifications, the potential of
these modifications to mitigate residential IAQ
problems, the pollutant sources they are most likely to
impact, and their potential limitations. This study was
not intended to determine definitively whether the IAQ
control options studied are reliable and cost-effective.
This report summarizes the results of Phase II.B of this
project, which consisted of three main efforts:
computer simulations of contaminant levels with IAQ
control retrofits, evaluation of the effectiveness of
the IAQ control retrofits, and development of
recommendations for future research. In Phase II.A of
the project, NIST used the multizone airflow and
pollutant transport program CONTAM93 to simulate the
pollutant concentrations due to a variety of sources in
eight buildings with typical HVAC systems under
different weather conditions. In Phase II.B, the
simulations were repeated after modifying the HVAC
systems with three IAQ control technologies -- an
electrostatic particulate filter, a heat recovery
ventilator, and an outdoor air intake damper on the
forced-air system return. The impact of these IAQ
control technologies on indoor pollutant levels was
evaluated by comparing average and peak pollutant
concentrations for the modified cases to the
concentrations determined for the baseline cases.
Simulation results indicate that the system
modifications reduced pollutant concentrations in the
houses for some cases. However, the heat recovery
ventilator and outdoor air intake damper increased
pollutant concentrations in certain situations involving
a combination of weak indoor sources, high outdoor
concentrations, and indoor pollutant removal mechanisms.
In cases where the IAQ controls reduced pollutant
concentrations, they led to larger relative reductions
in the tight houses than in the houses with typical
levels of airtightness, though the typical houses still
had lower post-control concentrations. The controls had
the largest impact on concentrations of non-decaying
pollutant from a constant source. Limited system
run-time under mild weather conditions was identified as
a limitation of IAQ controls that operate in conjunction
with forced-air systems. Another important objective of
the project was to identify issues related to the use of
multizone IAQ models and to identify areas for follow-up
work. Recommendations for future research include:
additional simulations for other buildings, pollutants,
and IAQ control technologies; model validation; model
sensitivity analysis; and development of a database of
model inputs.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899