Abstract
Point Daylight Factor (DFP) has been used for daylighting design in Sweden for more than 40 years. Progressive densification of urban environments, in combination with stricter regulations on energy performance and indoor environmental quality of buildings, creates complex daylight design challenges that cannot be adequately solved with DFP. To support a development of the current and future daylight indicators in the Swedish context, the authors have developed a comprehensive methodology for the evaluation of daylight levels in existing buildings. The methodology comprises sample buildings of various use and their digital replicas in 3D, detailed numerical simulations and correlations of diverse DF metrics in existing buildings, a field investigation on residents’ satisfaction with available daylight levels in their homes, and a comparison between the numerical and experimental data. The study was deliberately limited to the evaluation of DF metrics for their intuitive understanding and easy evaluation in real design projects. The sample buildings represent typical architectural styles and building technologies between 1887 and 2013 in Gothenburg and include eight residential buildings, two office buildings, two schools, two student apartment buildings, and two hospitals. Although the simulated DFP is 1.4% on average, i.e., above the required 1%, large variations have been found between the studied 1200 rooms. The empirical data generally support the findings from the numerical simulations, but also bring unique insights in the residences’ preferences for rooms with good daylight. The most remarkable result is related to kitchens, typically the spaces with the lowest DF values, based on simulations, while the residents wish them to be the spaces with the most daylight. Finally, the work introduces a new DF metric, denoted DFW, which allows daylighting design in early stages when only limited data on the building shape and windows’ arrangement are available.
Highlights
Point Daylight Factor (DFP ) is an official criterion for daylighting design of buildings in Sweden.It was introduced after the 1970’s energy crisis to secure a minimum daylight quantity in indoor environments and, thereby, to counterbalance stricter regulations on limited energy use for space heating [1]
Energies 2019, 12, 2200 perceived quality of daylight in a space, where the latter according to [2,3,4] is composed of both physical metrics and psychological criteria, its simple definition and resource-efficient evaluation during the building design have determined its decades long presence in the Swedish building regulations [5]
To get good insight into the available amounts of daylight in buildings, it was decided the study would be performed on existing buildings and by using DF metrics that were known to daylight designers in Sweden
Summary
Point Daylight Factor (DFP ) is an official criterion for daylighting design of buildings in Sweden. It was introduced after the 1970’s energy crisis to secure a minimum daylight quantity in indoor environments and, thereby, to counterbalance stricter regulations on limited energy use for space heating [1]. The minimum requirement for DFP has been set to 1% at a specified point in an indoor space where people stay for a longer time and where the nature of their activities requires access to daylight. Energies 2019, 12, 2200 perceived quality of daylight in a space, where the latter according to [2,3,4] is composed of both physical metrics and psychological criteria, its simple definition and resource-efficient evaluation during the building design have determined its decades long presence in the Swedish building regulations [5]. As pointed by national experts in daylighting design [6], the 1%
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