"Daylight levels in Swedish buildings as a base for modernized regulations" by Marie-Claude Dubois
Marie-Claude Dubois (SE)
Lecture from the 7th VELUX Daylight Symposium “Healthy & climate-friendly architecture– from knowledge to practice” that took place in Berlin on 3-4 May 2017. For more information visit http://thedaylightsite.com
“Daylight levels in existing Swedish buildings as a base for modernized national regulations” by Marie-Claude Dubois and Paul Rogers. Daylight has always been a precious commodity in Sweden but recent trends towards urban densification coupled with stringent energy and acoustic requirements jeopardize basic daylight access. Poor daylight access is not only connected to poor indoor environments but also to an increased dependency on electrical lighting. Previous research indicates that in Swedish residential buildings, better daylight utilization could potentially yield a 25% reduction of electricity use for lights.
While mandated daylight levels provide a potential safeguard against poor daylighting, daylight requirements were largely ignored until the environmental certification system Miljöbyggnad was introduced in 2005. Within this scheme, compliance with the building code’s point daylight factor criteria is compulsory. As this certification scheme has gained in popularity, so too has interest in the national regulations. Unfortunately, the current regulations are based on outdated calculation methods. Furthermore, there is a lack of evidence supporting its mandated threshold of a 1% point daylight factor (DFp) at half room’s depth. With the aim of providing valuable information to the authorities in their update of the building code, an exhaustive simulation study of daylighting in the existing residential building stock was undertaken.
This paper presents a cross analysis of the output data, drawing relations between building age, context, height, orientation and daylight performance metrics. A total of 100 buildings were chosen to represent common Swedish multifamily housing typologies built between 1875 and 1990. These buildings were modelled using Rhinoceros, DIVA and Grasshopper/Honeybee suite. The process entailed calculating nearly fifteen- thousand rooms in their surroundings. Results show that while the average DFp value for all the studied rooms is clearly above 1%, this threshold is not met in approximately half of the rooms tested. Kitchens generally obtained the lowest daylight levels in spite of the fact that inhabitants expressed their need for higher daylight levels in these rooms.
Buildings in urban contexts fared poorly but perhaps most surprising was the fact that of all the buildings tested, only eight were fully compliant. Another important finding is that the code’s simplified method based on window to floor area ratio had limited applicability due to geometric limitations inherent in the method. In summary, the findings of this study support the need for a fundamental reformulation of the current Swedish daylight legislation as it pertains to multi-family residential build- ings. Particularly so if the regulations are to successfully maintain a balance between daylighting and urban densification. Marie-Claude Dubois is associate professor at the Division of Energy and Building Design at Lund University, Sweden and environmental specialist at White Architects, Malmö, Sweden.
She has previously been associate professor (2003-2010) at Laval University, in Canada, and senior researcher (2001-2003) at the Danish Building Research Institute after award of her PhD in Construction and Architecture at Lund University (2001). She has contributed as author or co-author to some 100 scientific communications mainly in the field of daylighting, energy-efficient buildings, and sustainable architecture. She has also participated in the lighting and energy design or environmental certification of more than 30 buildings around the world. In her career, she has been leader of Subtask D of International Energy Agency IEA-SHC Task 50 on “Advanced Lighting Solutions for Retrofitting Buildings” and of Subtask B of IEA Task 40 on “Solar Energy and Architecture”.
Paul Rogers is an architect and Sustainability Coordinator at BAU Architects in Stockholm. A registered BREEAM assessor, he leads a division of three daylight specialists working with daylight certification of buildings. He is founder of the LinkedIn discussion forum ‘Svensk dagsljusberäkning’ (Swedish daylight calculation) which has nearly 300 members. Along with select members of this group, he is working to advance domestic daylight certification methodologies and to help Swedish Building code authorities modernize the country’s daylight regulations. He is also founder of an ongoing initiative which challenges Swedish urban planning authorities to better integrate daylight into municipal planning process.