Landscape offices at high latitude: daylight autonomy and electric lighting savings in relation to key design features

This paper presents a parametric study about daylight autonomy and electric lighting consumption in a typical open-plan (landscape) office space located at high latitude. The parameters studied include: furniture, climates and latitude, orientations, glazing-to-wall ratios (GWR), Venetian blind use and electric lighting control systems. The study is carried out using DAYSIM, which is based on the validated backward raytracing simulation program RADIANCE. The results indicate that the furniture can significantly reduce daylight autonomy, especially at the back of a deep room, and this parameter must therefore be considered seriously in future simulation work. Furthermore, the results show that daylight autonomy is good to excellent in Stockholm-Östersund and good in Kiruna for work stations next to the window, even on North facades. The North façade has the advantage of no direct sunlight glare compared to South. However, daylight autonomy is much more limited on the North orientation for work stations located a few meters away from the window, which suggests that deep open-plan offices with North orientation should generally be avoided. An examination of electric lighting pattern use confirmed results of earlier studies i.e. the selection of control strategy for the electric lighting system is more important than the selection of GWR and that the occupancy switch on/off system yields the highest energy use while a perfectly commissioned photoelectric dimming system can achieve very significant energy savings for all GWR, orientations and climates, compared to a manual switch at the door.