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Cost Analysis of Indoor Air Control Techniques

Several studies have been completed addressing the costs and the cost-effectiveness of alternative IAQ control measures.

Methodology for Cost-Effective Selection of IAQ Control Options
A simplified methodology has been defined that can be used by indoor air quality (IAQ) diagnosticians, architects/engineers, building owners/operators, and the scientific community, for preliminary comparison of the cost-effectiveness of alternative IAQ control measures for any given commercial or institutional building. Such a preliminary analysis could aid the user in initial decision-making prior to retaining experts (such as HVAC engineers and building modelers) who could conduct a rigorous evaluation.

This preliminary methodology has been published in an EPA report entitled "A Preliminary Methodology for Evaluating the Cost-Effectiveness of Alternative Indoor Air Quality Control Approaches" (EPA-600/R-99-053; NTIS PB99-156184, June 1999). (Abstract)

This preliminary methodology consists of text, logic diagrams, and detailed worksheets (including reference tables) that are intended to aid the user in:

The methodology addresses the following IAQ control options:

The cost data that were used in developing this methodology were obtained from the following sources:

As used here, the term "cost-effectiveness" refers to the incremental increase in annualized cost per unit reduction in exposure by the building occupants. "Exposure" is the number of person-hours per year during which the occupants are exposed to a unit concentration of the contaminant of concern; in this report, the units of exposure are (mg/m3)-person-hr/yr. The most cost-effective control approach is the one offering the lowest annualized cost per unit reduction in exposure.

Energy Costs of Increased Ventilation in Humid Climates (DOE-2 Modeling)
A series of computer runs has been completed using the DOE-2.1E building energy model, simulating a small (4,000 ft2) strip mall office cooled by two packaged single-zone systems, in a hot, humid climate (Miami, FL). These simulations assessed the energy penalty, and the impact on indoor relative humidity (RH), when the OA ventilation rate of the office is increased from 5 to 20 cfm/person in this challenging climate to improve indoor air quality. One objective was to systematically assess how each parameter associated with the building and with the mechanical system impacts the energy penalty resulting from increased OA. Another objective was to assess the cost and effectiveness of off-hour thermostat set-up (vs. system shut-down), and of humidity control (using overcooling with reheat), as means for reducing the number of hours that the office space is at an RH above 60% at the 20 cfm/person ventilation rate.

The results of this analysis have been published in an EPA report entitled "Energy Costs of IAQ Control Through Increased Ventilation in a Small Office in a Warm, Humid Climate: Parametric Analysis Using the DOE-2 Computer Model" (EPA-600/R-97-131; NTIS PB98-113368, November 1997). (Abstract)

Cost Analysis of Air Cleaners for Removing VOCs from Indoor Air
A cost comparison has been conducted of 1 m3/s indoor air cleaners using granular activated carbon (GAC) vs. photocatalytic oxidation (PCO), for treating a steady-state inlet volatile organic compound (VOC) concentration of 0.27 mg/m3. The commercial GAC unit was costed assuming that the inlet VOCs had a reasonable carbon sorption affinity, representative of compounds having four or more atoms (exclusive of hydrogen). A representative model PCO unit for indoor air application was designed and costed, using VOC oxidation rate data reported in the literature for the low inlet concentration assumed here, and using a typical illumination intensity. The analysis shows that, for the assumptions used here, the PCO unit would have an installed cost more than 10 times greater, and an annual cost almost 7 times greater, than the GAC unit. It also suggests that PCO costs cannot likely be reduced by a factor greater than 2 to 4, solely by improvements in the PCO system configuration and reductions in unit component costs. Rather, an improved catalyst having a higher quantum efficiency would be needed, increasing reaction rates and reducing illumination requirements relative to the catalysts reported in the literature. GAC costs would increase significantly if the VOCs to be removed were lighter and more poorly sorbed than assumed in this analysis.

This analysis has been published in a journal article entitled "Cost Analysis of Activated Carbon Versus Photocatalytic Oxidation for Removing Organic Compounds from Indoor Air" (Journal of the Air and Waste Management Assoc., October 1998). (Abstract)

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