Carefully planned use of natural light for indoor lighting has positive effects on the overall building energy demand. Because of the variable nature of daylight and in order to avoid visually unacceptable conditions, this must be done in a controlled way, which is possible using advanced daylighting systems. It requires also an electronic control of the supplementary artificial lighting. The performance of such combined systems is not yet understood in a quantitative way. Two issues are crucial for the success of any integrated daylighting/controls system: the energy savings and the user acceptance.
A minimum of 2 and a maximum of 4 systems will be evaluated both in practice and under laboratory conditions. The evaluation includes both energy saving potential and user acceptance. This way it is anticipated to develop a method for the performance prediction of real systems on the basis of simple laboratory tests.
The overall system performance must be evaluated in direct comparison to conventional systems, i.e. windows without any electronic controls. The performance evaluation must include the artificial lighting system and the appropriate controls. It is not sufficient to measure workplane illumination levels. Luminance distributions are probably more important and shall be evaluated as well. The comparison will be performed in defined, unused full-scale test rooms. In order to provide methods for future comparative evaluation studies, parallel investigations using scaled models under an artificial sky and computer simulations will be carried out, compared to the test room results, modified, if necessary, and validated.
The user reaction is determined in three different ways: One of these methods is based on computer simulation by creating a static virtual reality. This is important for the inclusion of natural daylight in subjective test procedures: it is the only way to ensure reproducible test conditions. Another method is questioning office workers under specific conditions. The advantage is that subjectives are in a real environment with their work and movement etc.. The third method uses objective testing of persons with respect to measurable criteria. The disadvantage of tests in reality is that test conditions with daylight are not reproducible.
Expected Achievements and Exploitation
Having both at hand: a standardized test procedure and a reliable user assessment prediction, it will be possible to make realistic assessments of the energetic impact of daylighting technologies on buildings.
Funding SchemeCSC - Cost-sharing contracts
2628 VK Delft
5600 JM Eindhoven