Urban densification affects daylighting: existing daylight levels in Swedish multi-family housing as a base for future daylight requirement

This article presents the results of a study of the Swedish multi-family housing stock in relation to its daylight performance under overcast sky conditions. A total of 8573 rooms in 35 existing buildings were investigated using advanced lighting simulations to determine their point daylight factor, as defined in the current building regulations. The buildings were selected based on their architectural typology and construction era. The results show that, on average, the existing rooms meet the current daylighting requirement (point daylight factor DFp of 1%). The window sky exposure factor was found to affect the DFp significantly. Rooms with a large sky exposure angle that failed to meet the requirement were deep rooms or rooms with a small window-to-floor ratio. The general conclusion is that the current requirement can be considered realistic to ensure an adequate provision of daylight in multi-family dwellings.