Electric lighting in a single family house in relation to daylight availability for real users.

Daylighting strategies in building design can lead to reduce of the energy consumption for electric lighting. However, the potential energy saving for electric lighting is highly dependent on user’s behaviour. While in office buildings the standardized user’s behaviour reveals a robust correlation between daylight availability and the electric lighting energy use, in residential buildings this relationship is not so straightforward. The aim of this study is to investigate if the availability of natural light is related to a decreasing of the electric energy use for lighting, analysing the actual users’ behaviour in three different rooms of a single family house in Trondheim (Norway). The investigation is based on a set of data collected during a monitoring experiment that took place in the ZEB Living Lab. The ZEB Living Lab is a single family house located in Trondheim at the NTNU Campus. It is equipped with a monitoring system that keeps track of the electric and thermal energy use as well as the outdoor boundary conditions. During the winter 2016, six different users’ groups lived alternatively in the house. In this occasion, the complete users’ behaviours were monitored. These data include information about the use of electric lighting as well as the outdoor daylight condition. Experimental and numerical analyses were carried out in order to compare the use of artificial lighting against daylight availability. Through experimental and numerical analyses, it was possible to estimate the actual electric energy use and the indoor daylight illuminance in the interiors of the house and therefore determine the correlation using the Pearson’s coefficient. The results show weak correlation between daylight availability and the electric energy use. A different users' behaviour in the sleeping and the living area was found. The former is generally unoccupied during the day, since no use of electric lighting was recorded in most of the cases, showing a degree of carefulness in user. However, in residential context, the use of electric lighting weakly depends on the indoor daylight availability.