Occupant satisfaction and ventilation strategy - a case study of 20 public buildings.

Occupant response in a good indicator of the effectiveness of a ventilation system. In a one-year study in the province of Quebec region, 20 public buildings were studied. Occupants were asked to answer questions on their perception of their environment and the ventilation at their workstation. Annual energy consumption for each building was recorded. The ventilation systems were studied as well as their rates; minimum outdoor air rates and average total air rates, at each workstation and at the ventilation system. Ventilation rates were plotted against energy consumption. Occupant satisfaction was plotted against ventilation rate and against energy consumption. It was found that as outdoor air rates at the work stations increased, the occupants perceived a better indoor air quality, a better ventilation, and a more constant ventilation frequency above 70 l/s/p. No trend was found from their perception of the air movement. As the total air supplied at the diffusers increased, the occupants perceived a better indoor air quality, a better ventilation, and a more constant ventilation frequency above 110 l/s/p. However, all these perceptions decreased to the original values above 130 l/s/p. No trend was found from their perception of the air movement. As the total air flow rates at the ventilation system increased, the occupants perceived a better indoor air quality, a better ventilation, a more constant ventilation frequency, and a better air movement above 200 l/s/p. However, all these perceptions decreased to the original values above 250 l/s/p. As the ventilation efficiency at the workstations increased from 27 to 70%, the occupants perceived a poor indoor air quality, an insufficient ventilation, and an irregular ventilation frequency above 25%. No trend was found from their perception of the air movement. As the maximum carbon dioxide concentration at the work place increased, the occupants perceived a worst indoor air quality above 800 ppm of CO,, a worst air movement above 1000 ppm. The ventilation strategy resulting in the best perception from the occupants was of the type free cooling, with variable outdoor air supply, variable total air supply, and constant supply temperature.