Daylight in offices: A comparison between the Dutch and European standards for daylight in buildings

The current Dutch standard for daylight in buildings does not assure good daylight quality.Designers therefore often do not know when a building has good daylight quality and how they can design a visually comfortable and healthy building.The new European standard for daylight in buildings is more elaborative and recommends a higher daylight quality. When this standard is introduced, the assessment method must be adopted in the Dutch building regulations. The assessment method however differs a lot from the current Dutch assessment method, which makes it difficult to compare the standards and determine the exact differences.To make it easier to design buildings with good daylight quality, the goal of this research was to establish a set of recommendations. For these recommendations, it was necessary to compare the Dutch and European standards. Three aspects of the standards were considered in this research: the requirements, the assessment methods and the effects on daylight quality.Literature review on the standards gave insight in the requirements and assessment methods. The most obvious difference was that the European standard is more elaborative and assess, besides daylight, also sunlight, glare and view. Another big difference is that the Dutch standard is normative and the European standard descriptive. Both standards do not consider the orientation of a building and opposite obstructions. After a literature study, two case studies were performed. The assessment of daylight in a basement showed that a space that meets the Dutch standard, can have a really bad daylight quality. It also led to the orientation factor which can be used to convert simulated daylight factors. This can be useful to gain insight in the amount of daylight in a space in common situations when the sky is not completely clouded and sunlight influences the daylight quality a lot.The second case had quite good daylight quality, but still did not meet the European standard. There is not enough daylight, at the south east side there is too much glare, and at the north west side there is not enough exposure to sunlight.The last part of the research was a systematic study. Variants were simulated according to the Dutch and European standard. Variants with a minimum daylight area from the Dutch standard had a bad daylight quality and showed that the window shape influences the access of daylight. In almost all other variants with bigger windows, higher reflection factors, or less obstructions, itwas not possible to meet the European standard on both side of the building. This means that in a dense area the European standard is almost unachievable. Because of the many influencing factors, there is no clear relation between the equivalent daylight area and the daylight factor.For designers it is recommended that they consider the orientation, surroundings and reflection factors, even though it is not required according to the standards. This gives a more realistic insight in the daylight quality. Rooms should comply with a minimum daylight factor of 0.8% in 50% of the area and an average daylight factor of 1.5% also in 50% of the area. Besides the amount of daylight, sunlight, glare and view also influence the daylight quality and should be taken into account during the design process.Of course, there might be more factors that should be considered by designers. Those are not mentioned in this research, but can be investigated in future research.Architecture, Urbanism and Building Sciences | Building Technology | Sustainable Desig