Indoor Air Quality Cost Comparisons in Three Typical Buildings

The options of increased ventilation and/or increased filtration to improve indoor air quality in existing buildings were compared. Three buildings, located in Greensboro, N.C., were studied in order to predict the construction, retrofit, and operating costs associated with each option. The analyses included reviews of the building design drawings; site visits and inspections of the heating, ventilating, and air-conditioning systems; review of construction costs; and review of annual utility bills. Retrofit costs were estimated based on supplier quotations for equipment and construction labor estimating guides. Increases in annual maintenance costs were based on the replacement costs of filters plus 5 of the cost of all additional equipment installed. Changes in energy costs were projected using the ASEAM computer simulation program. For each building, the outdoor air was increased from its current operating amount to 100 outdoor air. Similarly, particulate and gas-phase filtration was incrementally increased to filter efficiencies of 95. The retrofit and operating costs and the estimated reduction in indoor air contamination levels were projected. A final costs comparison of alternatives was computed based on a system performance that would reduce indoor air contamination by 80. As expected, meeting the performance target was most costly for the building with split system heat pumps. The building with rooftop units, economizer cycle capability, and a central exhaust system was less expensive. The building with the chilled water system and air handling units with economizer cycles was least expensive. This last building, however, had the highest initial construction cost.