Daylighting and sunlighting in street canyons. A quantitative research on the visual perception and in-situ daylight measurements of four urban canyons in Copenhagen.

Abstract

“Light creates ambience and the feel of a place, as well as the expression of a structure.”
Le Corbusier

With the current urban pressure and large waves of immigration, cities are facing an increase in population and therefore urban densification. This increase in building quantities affects daylight reaching the public space. City densification is easily readable in large metropolitan areas, while its effect is less noticeable in the Nordic countries. However, in such a context where natural light is scarce throughout the year and skies are consistently cloudy, daylight is of great importance. This thesis is based in Copenhagen and is a thorough analysis of the daylight and sunlight parameters that define the visual comfort in the outdoor environment. Four urban canyons, each with different geometry, orientation, materiality and use, were selected as case studies. The research is composed of two parts. The first part consisted of in-situ measurements and calculations, in particular: luminance; illuminance; HDR photographs; false-color diagrams; material reflectance; Daylight Factor and Vertical Daylight Factor. The second one, based on questionnaires, was a thorough investigation of daylight level, daylight adaptation, daylight quality, daylight distribution, visual comfort, sunlight, glare and a qualitative investigation of the feeling of space. The main research question aims at developing a relationship between parameters that defines the optimal urban canyon in terms of visual comfort. The sky condition was found to be a driving force along with other subjective reasons given by people, such as their personal background, urban density or geographical locations of their origins. However, the general conclusion emphasized the importance of the material and its key role on the visual perception of daylight. The material itself has several properties that define its visual performance, such as color contrast, reflection and specularity. The correct combination of these properties can create a different impression even if the geometry remains the same. These conclusions show the complexity of the topic and how subjective assessments are intertwined with daylight metrics. This research opens the door to future research on the subject of outdoor daylight and sunlight perception, for architects and designers alike.

Popular Abstract

This paper focuses on the visual perception of daylight and sunlight in an outdoor urban context in Copenhagen, and the parameters that define visual comfort.

Cities are facing an increase in population and therefore urban densification due to the current urban pressure and large waves of immigration. This increase in building quantities affects daylight reaching the public space.

The case studies are four urban-street canyons, with different geometry, orientation, material and use. The research is composed of two parts. The first part consisted of in-situ measurements and calculations, in particular: luminance; illuminance; HDR photographs; false-color diagrams; material reflectance; Daylight Factor and Vertical Daylight Factor. The second one, based on questionnaires, was a thorough investigation of daylight level, daylight adaptation, daylight quality, daylight distribution, visual comfort, sunlight, glare and a qualitative investigation of the feeling of space. For this research are completed 192 questionnaires covering two sky conditions, fully overcast and sunny.
The sky condition was found to be a driving force along with other subjective reasons given by people, such as their personal background, urban density or geographical locations of their origins. However, the general conclusion emphasized the importance of the façade material and its key role on the visual perception of daylight. The material itself has several properties that define its visual performance, such as color contrast, reflection and specularity. The correct combination of these properties can create a different impression even if the geometry remains the same. The integration of these material properties with other components such as geometry, direct sunlight, or the presence of glare could create different impressions for the same space.
These conclusions demonstrate the complexity of the topic and how subjective assessments are linked to daylight metrics. This research will help future designers to further investigate the subject of outdoor daylighting and the impact of façade design on the outdoor visual perception. In order to achieve visual comfort, which is a very relative concept, designers should comply with some degree of discomfort in order to have their best design performance. In Copenhagen, which most of the year is characterized by cloudy conditions, it is essential to have high outdoor daylight levels. Therefore, it implied that a certain visual discomfort can be tolerated in sunny conditions so that the rest of the year has good daylight conditions. The above-mentioned relations and factors contribute to the visual perception of urban space, its comfort and the sense of belonging.

• author: Lami, Olesja
• supervisor: Marie-Claude Dubois
• organization: Department of Architecture and Built Environment; Division of Energy and Building Design
• course: AEBM01 20181
• year: 2019
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: daylighting, sunlighting, urban canyon, visual perception, visual comfort
• funder: Erasmus+ EU Programme
• language: English
• id: 8972033
• date added to LUP: 2019-02-27 08:12:39
• date last changed: 2019-02-28 13:02:11