An Ideal Window Area concept for energy efficient integration of daylight and artificial light in buildings

There have been many developments in energy efficiency in buildings in the last few decades, but many new buildings are still not designed whereby daylight is efficiently integrated with the artificial lighting system. In cases where there is integration, the potential for energy savings to be made on lighting is not always assessed. This paper presents a methodology to predict the potential for energy savings on lighting using an Ideal Window Area concept when there is effective daylight integration with the artificial lighting system. The methodology was developed by using rooms of ten different dimensions and five different room ratios. The energy analysis work was performed using the VisualDOE programme for the climatic conditions of Leeds, in the UK, and Florianópolis, in Brazil. Following this, the potential for lighting energy savings was assessed for each room using a method based on Daylight Factors. It was observed that the potential for energy savings on lighting in Leeds ranged from 10.8% to 44.0% over all room sizes and room ratios for an external illuminance of 5000 lux; and in Florianópolis, the potential ranged between 20.6% and 86.2% for an external illuminance of 10000 lux. The methodology presented can be applied to any location around the world.