Advanced Window and Lighting Technologies in net Zero Energy Buildings

Light has an important visual and non-visual impact on humans. Most of our information exchange, especially within office working spaces, occurs through it, our circadian rhythms are directly influenced by its presence. On the other hand, artificial lighting is responsible for a large fraction of electricity consumption in non-residential buildings. The latter becomes even more dominant within net Zero Energy Buildings (nZEB) where yearly net heating and/or cooling loads are reduced almost to nil by the way of energy savings measures and renewable energy technologies. Anidolic Daylighting Systems (ADS) are very effective façade-integrated daylighting systems which can collect and redirect diffuse daylight deep into office rooms under almost any climatic conditions: several studies have demonstrated their efficiency in the Northern and Central European regions, as well in sub-tropical climates. Recent studies have shown that their integration with high efficacy electric light sources and efficient luminaries can lead to very low lighting power densities (e.g. 3 - 4 W/m2 instead of 12 – 15 W/m2), as well as an improvement of visual comfort, visual performance and contribution to human health. As such, they offer excellent opportunities to reduce the electric lighting load in solar buildings and nZEB. An integrated day- and electric lighting system has been implemented in the south-facing office rooms of the LESO solar experimental building located on the EPFL campus in Lausanne (Switzerland). Objective visual performance and subjective visual comfort assessments were carried with 20 subjects, confirming the adequacy of this approach regarding human response factors, as well as from an energy savings perspective. A ceiling integrated anidolic daylighting system was also implemented last year in an nZEB, located in Singapore and erected through the refurbishment of an existing building. The system was based on a former study carried out on the EPFL campus by the way of a 1:1 scale mock-up office room equipped with a comparable device. Significant electricity savings, as well as visual comfort and performance improvement, were also observed in this case.