Clean air effectiveness: An indicator for assessing the energy use implications of gas-phase air cleaning

Gas-phase air cleaning (GPAC) may improve indoor air quality by removing harmful pollutants. GPAC may be employed to substitute part of the outdoor air flow rate for the same resulting indoor air quality, thereby reducing energy use. For air cleaners to be adopted as potential energy saving solutions, a convenient method to evaluate the energy impact and air quality performance is needed. This study presents the development and assessment of the clean air effectiveness (CAE), an indicator which can be used to include the energy benefits for substituting outdoor air supply in the design process. To demonstrate the application of the CAE, a building simulation model assisted by experimental studies was used as a case study for assessing the implications of combining stand-alone air cleaners with a variable-air-volume ventilation system. Results show that the CAE can be used to select the optimum air cleaning system. It can be used to assess and compare the effectiveness of individual air cleaning systems or their effectiveness against ventilation systems responsible for providing clean outdoor air. Furthermore, air cleaning represents an air quality or energy saving measure in both cold and warm humid climates. For a fair comparison, heating and cooling energy use of the entire heating, ventilation, and air conditioning system should be included in the evaluation when comparing its effectiveness with the air cleaning solution. The number of air cleaners, flow rate, and control may be used to optimize the system towards the desired function, air quality or energy savings.