Concept: Urban heat island effect mitigation – Shadings
Alternative cooling strategies based on improved thermal protection of the building envelope, and on the dissipation of a building's thermal load to a lower temperature heat sink, appear to be very effective.
These strategies and techniques known as passive and hybrid cooling have already reached a serious level of acceptance from both the technical and scientific experts.
The present document aims to inform and provide knowledge and recommendations on the use of artificial solar control devices in cities.
Technologies dealing with the solar control of open spaces is one of the most important strategies for heat gain prevention. Their role focuses on the prevention of solar gains on landscape surfaces, occupant clothing or skin. The way outdoor spaces are used as well as the duration and intensity of the use depends highly on how comfortable they are. It is possible to control the climate of outdoor spaces by modulating the heat flows that determine thermal comfort levels, like the direct or diffuse solar radiation on the human body as well as the infrared radiation received by the human body by the surrounding surfaces, Figure 1.
Figure 1: Heat flows over the human body in an outdoor space. Source (1).
Provision of solar control in outdoor spaces reduces the intensity of direct and diffuse solar radiation on the human body, while it keeps the surrounding opaque surfaces (pavements, roads, walls, etc.), at low surface temperature. As a result, the infrared radiation emitted by the surrounding environment to the human body is considerably lower, while opaque surfaces of low temperature contribute to decreasing the ambient temperature as well.
Solar control of outdoor spaces can be achieved either by using trees and other green spaces or using dedicated artificial shading devices.
Solar control of outdoor spaces offers important health benefits protecting humans from skin cancer. As reported by the World Cancer Research Fund, 300,000 new cases of skin cancer were reported in 2018, (2).
The design of solar control devices in cities should present a very high aesthetic value to be accepted by the visitors and the local population. In parallel, they should not significantly restrict the levels of daylight especially during the winter period while satisfying the proper air flow between the shaded area and the surrounding zones.
Shading of Open Public Spaces
Figure 2 : Vainiai Palace Rehabilitation Senatorių Pasažas , Vilnius, Lithuania, (3)
Figure 3. Coffee Shop, Public Space, Jerusalem, (4).
Figure 4. Public Space, Renovation, China, (5).
Figure 5: Solar Control of Public Spaces, Preston, UK, (6).
Figure 6 : Public Space, Pier, Bruges, Belgium, (7).
Figure 7: Public Space, Bus Station, Rotterdam, The Netherlands, (7).
Shading of streets
Figure 8: Street-Shade in Madrid, (8).
Figure 9: Shading of a street in Lisbon, Portugal, (9).
Figure 10: Metal Shading in Darwin, Australia, (10).
Figure 11. Metal and Glass Shading in Singapore, (11).
Figure 12. Shading of a street in Pato Bragado, Spain, (12).
MATURITY:
Urban solar control systems are very mature mitigation techniques. Proper architectural and engineering design of the shading systems can contribute to improved outdoor thermal comfort and mitigating urban overheating. Most of the used components are industrial systems well tested under adverse conditions.
