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Indoor Air Quality Impacts of Residential HVAC Systems. Phase II.B Report: IAQ Control Retrofit Simulations and Analysis.


pdf icon 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.