Daylighting in environmentally certified buildings. Subjective and objective assessment of MKB Greenhouse, Malmö, Sweden

Abstract: What could be considered an adequate level of daylight in buildings has become a debated question in the Swedish building industry. The current daylight requirements are often found difficult to meet in practice, especially in combination with other requirements regarding energy use. Outdated daylight requirements in the national building code combined with limited knowledge about the subjective impression of daylight in residential buildings are two issues that form the bottleneck around the question of daylight and energy in buildings. Daylight is of great importance to our health and well-being. It is thus important to identify an adequate daylight level while defining an appropriate expression of this level through relevant daylight metrics in building codes and certification systems. This study focuses on the tenants’ subjective impression of the daylight conditions in the apartments of MKB Greenhouse, Malmö, Sweden. The goal of this study is to link the subjective impression of daylight to objectively measured and simulated data. This study contributes to knowledge in the field that will help to determine suitable daylight conditions in future energy efficient multi-family dwellings. Self-administered questionnaires are used to collect information about the subjective impression of daylight in Greenhouse. Physical measurements are carried out and existing daylight simulations are further analyzed and discussed in relation to both measurements and subjective assessments. The subjective assessments show that the respondents have a clear preference for daylighting and that their perception of daylight level is affected by other parameters than the daylight factor alone. The objective assessment shows that the daylight factor (DFp) varies between 0.8-1.2% in the main living spaces of the apartments. Linking the objective results to the subjective ones, the results of this study is that the objective daylight level does not correspond to the expected level of subjective satisfaction. The final conclusion is thus that a lower threshold than the current (DFp ≥ 1.2%) is not recommended.