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


Campaigns

We have conducted three social campaigns so far, focusing on studying the relationship between climate, urban space, and people. Through online and on-site surveys, on-site measurements and workshops, we have investigated people’s thermal perception, their attitudes and beliefs about urban warming, their preferences for specific heat mitigation strategies, and their willingness to contribute / pay to improve their neighbourhood’s thermal comfort. Through these studies, we also aimed to communicate the importance of citizen engagement in policy-making as well as planning neighbourhoods in Singapore in order to improve residents’ thermal comfort and encourage their outdoor activities. More than 2500 Singapore residents have participated in the campaigns. The social studies have been conducted in collaboration with Singapore University of Technology and Design (SUTD) and the local NGO Participate in Design (PiD).

An additional outdoor thermal comfort and daily mobility campaign (on-site survey, measurement and pedestrian counting) has been conducted in the  central Tanjong Pagar district. It specifically targets transiting pedestrians in their daily commutes. As the three social campaigns it may helps to characterize the walking habits and OTC thresholds of this specific population, highly subject to short-time variations of their thermal environments. More specifically, the role of air humidity in the overall perception and sensation of thermal discomfort in Singapore has been investigated.


 Measurement Study in Punggol (February 2018) / Source: Lina Meisen Photography 2018

Measurement Study in Punggol (February 2018) / Source: Lina Meisen Photography 2018