Shading device control: Effective impact on daylight contribution

Abstract

This paper presents the results of a project funded by the Swiss Federal Office for Energy that focused on the effective use of movable shading devices in offices, and on the impact on the indoor daylig hting availability. The first pa rt of the project consisted in the observation of the use of sunscreens when the command is not automated (office buildings, operating webcams from 01-02-2013 to 31-012014 over 125 openings, e.g. more than 500,000 individual blind positions analysed). The key finding is that sunscreens are adjusted infrequently (less than 2 movements blinds / week) regardless of the orientation or season. The consequence of this misuse is that the contribution of natural light is far from being optimised. The second part of the project focused on the simulation of the actual contribution of daylight in each of the observed rooms (Simulations DIAL + / Radiance). This allowed us to compare the results with those that would have been achieved with automated blinds. The results of these simulations were then used to estimate the electricity consumption for lighting. This study shows that the energy savings associated with automated blinds can reach several kWh/m 2 per room and per year. Comparison with SIA 380/4 calculations points out that the actual version of the Swiss Standard underestimates the potential related to blinds automation and also tends to overestimate the effects of artificial lighting automated control. The main conclusion of this study is that the implementation of automatic blinds can significantly increase the number of hours during which artificial lighting is not required while preserving the visual comfort and freedom of choice for users. The other conclusion is that the Swiss Standard should encourage the use of daylight by imposing specific targets on this topic.