F. Linhart* and J.-L. Scartezzini

Solar Energy and Building Physics Laboratory (LESO-PB),

Ecole Polytechnique Federate de Lausanne (EPFL), 1015 Lausanne, Switzerland
* Corresponding Author, friedrich. linharl@epfl. ch

Abstract

This article presents the results of a satisfaction assessment recently carried out amongst occupants of office rooms equipped with Anidolic Daylighting Systems. Questionnaires and complementary personal interviews were used to reveal which typical office lighting related problems are the most annoying to the occupants of the examined offices. The results show that occupant satisfaction within the examined offices is in general very good but that temporary daylight-overprovision and glare can sometimes cause considerable discomfort. The article concludes that window blind configuration, blind control as well as inappropriate handling by the occupants are the main reasons for the encountered problems and discusses different possibilities to deal with them.

Keywords: Daylighting, anidolic, office lighting, occupant satisfaction.

1. Introduction

Electric lighting often causes more than 30% of an office building’s electricity consumption [1]. The use of daylight (issued from the sun and the sky vault) for illumination purposes inside office buildings seems to be a very evident way to reduce a building’s electric lighting load. However, electricity savings do not come automatically with the installation of a sophisticated daylighting system. Lighting load reduction can only be ensured if the building’s occupants accept and agree to properly use this system. If, for example, building occupants override a sophisticated daylighting system by simply closing the window blinds and switching on artificial light in order to avoid glare related problems, then all effort was wasted. One main concern of architects and engineers should therefore be to develop daylighting systems that are easy to use and that allow the occupants to create a comfortable luminous environment within their office at all times.

The southern faqade of the LESO solar experimental building (LESO-SEB), located on the campus of the Swiss Federal Institute of Technology in Lausanne, is equipped with so-called Anidolic Daylighting Systems (ADS) [2]. These systems are based on the theory of non-imaging optics [3]: they transport a maximum of daylight from outside the building into its interior with minimal inter­reflections and minimal losses.

In order to get an insight into the occupants’ satisfaction and well-being when working within office rooms equipped with this type of faqade-integrated ADS, a detailed post-occupancy satisfaction assessment (based on questionnaires and personal interviews) has recently been carried out amongst 23 occupants of the LESO-SEB. The objective of this study was not only to find out whether occupants are satisfied with their office lighting or not, but also to identify weak spots in the lighting installation (e. g. within the ADS itself or the associated control system) and to find solutions for eliminating these weak spots.

This article first gives a detailed overview of ADS in general and the particular ADS installed within the LESO-SEB in Section 2. In Section 3, the results of the occupant satisfaction assessment are presented. Section 4 then outlines the lighting system’s identified weak spots and discusses possible ways to optimize occupant satisfaction within office rooms equipped with this type of ADS. A summarizing conclusion is given in Section 5.