Validation of multizone IAQ model predictions for tracer gas in a townhouse

To provide additional validation data for the multizone airflow and contaminant model, CONTAMW, experiments were performed in an occupied three-storey townhouse in Reston, VA. A tracer gas, sulfur hexafluoride (SF6), was manually injected within one room of the house and the concentration of SF6 was then measured in nine rooms. This same process was then recreated in CONTAMW and the resulting predictions were statistically compared to the measured values. A total of 10 experiments were conducted and simulated between May 2000 and June 2001. In four cases, the heating and air-conditioning system fan was operating. SF6 was injected in the recreation room (basement level), the kitchen= dining room (main level) and the master bedroom (upstairs level). A statistical comparison of measurements and predictions was performed per ASTM D5157 (ASTM 1997) for all cases. Comparisons were made for overall zone average concentrations and individual zone transient concentrations. The results for zone average concentrations were very good with many cases meeting most or all of the D5157 criteria. Several cases showed a poor to fair correlation between average measurements and predictions due to discrepancies with a single zonemdashthe main floor bathroommdashbut excluding that zone resulted in these cases meeting or nearly meeting the D5157 criteria. Comparisons of individual zone transient concentrations were mixed with many good to excellent cases but also numerous fair to poor. Zones other than the bathroom had occasional poor comparisons between predictions and measurements but no consistent discrepancies. The predicted SF6 concentration averaged over all zones and cases was within 10% of the average measured concentration.