The influence of human behaviour on the energy consumption in buildings

Occupant behaviour influences the amount of energy consumed to sustain a comfortable indoor environment. However, the extent to which occupant behaviour affects building energy consumption is largely unknown. The purpose of this study was to investigate the extent of this influence. This paper describes two studies using dynamic computer simulations of occupant behaviour in dwellings. The first study included simulations of a naïve and a rational behaving occupant. The naïve occupant controlled the indoor climate using an energy expensive behaviour, while the rational occupant controlled the indoor climate in an energy efficient way. The simulated occupant could manipulate six controls, such as turning on or off the heat and adjusting clothing. All control actions were carried out with the aim of keeping the PMV value within predefined limits. An energy consuming and an energy efficient behavioural mode were simulated. A reference simulation was made during which the occupant had no control over the environment. The occupant was able to keep the thermal indoor environment close to neutral when he/she had the possibility to manipulate the controls. The indoor environment was similar within each behavioural mode regardless of the PMV limits. However, the energy consumption in the energy consuming behavioural mode was up to 330 % higher than in the energy efficient behavioural mode. The second study was based on the results from simultaneous measurement of occupant behaviour, indoor and outdoor environment in 15 dwellings in Denmark during the period from January to August 2008. Based on the measurements occupant behavioural patterns were defined and implemented in the building simulation program IDA ICE. A case and a reference simulation were carried out. In the case, the behaviour patterns derived from the measurements were used while the reference used simulated behaviour patterns defined like they might have been by a consultant engineer. The simulated behaviour patterns resulted in large differences in indoor environmental variables between the two simulations. The heat consumption was more than three times as high in the case as in the reference simulation. This underlines the importance of considering the behaviour of the occupants in the design process of buildings.