Effectiveness of operable windows in office environments

A field study was conducted between November 2011 and March 2012 in nine modern office buildings in the Netherlands. One of the objectives was to objectify (under given weather conditions) how much control can be exercised by office workers over their indoor climate with operable windows. To evaluate the effectiveness of the operable windows, dynamic experiments were conducted. The experiments started with the opening of windows by the research team. Next, response times and step responses were assessed in terms of air temperature changes and CO2 concentration alterations. An average maximum outdoor temperature of 8 °C and an average wind speed of 4 m/s were measured during the study.
For the cases studied, as far as temperature effects are concerned: the study revealed that the step response on average was -2.2 K; the average halftime value was 8 minutes; and the temperature on average changed with -0.18 K per minute after windows were opened. As far as effects on CO2 concentrations are concerned: step response on average was -390 ppm; the average halftime value was 7 minutes; and the CO2 concentration on average changed with -37 ppm per minute after windows were opened. With some limitations, the outcomes can be used to quantify how effective operable windows can be -during the heating season- to office building users that periodically want to fine-tune their indoor climate.