2009 - Daylight Symposium
LONG TERM ASSESSMENT OF COSTS ASSOCIATED WITH LIGHTING AND DAYLIGHTING TECHNIQUES by Marc Fontoynont
Danish Building Research Institute, Aalborg University
Building lighting and daylighting systems disserve to be assessed over long periods of time (over 30 years) for optimization. The interest is to provide professionals and investors a way to compare the real cost of lighting solutions. This assessments must include product costs, installation costs, maintenance cost, and energy requirements. In our process, the lighting techniques are compared on the basis of illumination delivered on work plane (0.8 m from the floor) per year (Unit: Megalumen.hours/year). The currency is the Euro since all data were computed for the European environment. Performance of daylighting techniques were assessed using climatic data recorded in Lyon, France (Latitude 45.7°N). The selected daylighting techniques were: roof monitors, façade windows, borrowed light windows, light wells, daylight guidance systems, as well as off-grid lighting based on LEDs powered by photovoltaics. These solutions were compared with electric lighting installations consisting of various sources: fluorescent, tungsten and LED.
After classifying the total annual running costs associated to illumination delivered for each system, we found that standard daylighting techniques provide light in a cheaper way than electric lighting (3 to 20 times typically) with best performances reached by rooftops. However, if the objective is to bring daylight deep into building interiors, daylighting solutions appear expensive, except if daylighting guidance systems are employed (using highly reflective coating). Hence the necessity to approach optimal design of daylighting with care, giving high priority to roof systems and facade systems. Core daylighting techniques aiming at bringing daylight deeply in building interiors need a very careful financial assessment.
The study points out however, than if LED lighting options could be delivered at a third of today’s price (30 €/ Klm instead of 100 €/Klm today) LED could become a cost effective solution for indoor lighting, competitive to fluorescent lighting.
This study does not address the life cycle analysis and the environmental impact of lighting systems, which could make daylighting solutions even more appealing.
Marc Fontoynont, Professor, Director Laboratoire Sciences de l’Habitat, Département Génie Civil et Bâtiment, ENTPE. Vice president of CIE (International Commission on Illumination) and Director of CIE division 3. Vice- President of l’Association Française de l’Eclairage (AFE Paris). Marc Fontoynont is responsible for extensive research in the areas of optics, photometry, light distribution, luminous environment perception and daylight characterization.