Mitigation Strategy Assessment Using ENVI-met

Using climate modelling techniques, strategies for improving outdoor thermal comfort (OTC) were assessed specifically for green- and brown-fields in Singapore. In collaboration with two Singaporean Agencies, Urban Redevelopment Authority (URA) and Housing Development Board (HDB), we designed and modelled several specific strategy scenarios for test areas in the Jurong Lake District, in the Central Business District and in an HDB estate in Punggol. These scenarios were composed by measures including vegetation, urban geometry and surface materials, aiming to improve the wind flows and reduce heat storage. Using micro-scale computational fluid dynamics (ENVI-met model) we were able to study the thermal environment under different annual meteorological conditions at the building and neighbourhood scale. We conducted a spatio-temporal analysis that included a sensitivity analysis as well as a thermal comfort exposure mapping for each specific test area. Specific climate-responsive planning guidelines with quantitive and qualitative recommendations will be developed.

 Source: Lea Reufenacht  Top (left to right): Increase setbacks on ground floor from 4 to 9 meters; Re-arrange and re-orientate punctual buildings blocks; Adjust height, location and form of C-walk. Bottom (left to right): Increase number of trees (33% and 60%); Install large-scale urban canopy/pergola to increase shading; Retrofit pavement and façade materials with green facades and retro-reflective materials at different heights.

Source: Lea Reufenacht

Top (left to right): Increase setbacks on ground floor from 4 to 9 meters; Re-arrange and re-orientate punctual buildings blocks; Adjust height, location and form of C-walk.
Bottom (left to right): Increase number of trees (33% and 60%); Install large-scale urban canopy/pergola to increase shading; Retrofit pavement and façade materials with green facades and retro-reflective materials at different heights.

Some of the results for Singapore are:

  • It is relevant to use reference weather types to analyze OTC throughout the year

  • Porosity and increasing ventilation can improve OTC in courtyards and open areas

  • Green facades can only have an impact on OTC in areas very close to them (< 2 - 4 m). Orientation of the facade affects significantly its outdoor thermal performance.

  • Green roofs have little impact on OTC, if applied only locally.

  • Shadowing of trees might not be sufficient to attain an acceptable OTC level in low wind conditions (during midday and afternoon).

  • Void deck can improve ventilation and thermal comfort levels in outdoor spaces (e.g. courtyards).

  • New developments can increase one category the thermal comfort level (e.g. from warm to hot) in already existing developments