As we spend 90% of our time indoors, the places where we live, work, study and play inevitably affect our well-being. Faced with such complex interactions between the built environment and human activities, SDE consciously integrates domain knowledge from other fields to understand these interactions as part of our efforts to improve living and environmental outcomes.
SDE adopts well and green thinking in our pedagogy and research that emphasises human-centric design within a sustainable natural and built environment. To do this successfully, we collaborate with experts from fields such as medicine, public health, engineering, computing, as well as the social sciences to craft integrated and holistic solutions for our communities.
Urbanisation creates cities that have higher concentrations of man-made structures and materials, and less natural vegetation. This produces a hotter and more polluted urban climate as human activities generate heat and pollutants that are trapped and disperse slower to the surroundings. The imbalance results in a phenomenon known as the Urban Heat Island (UHI) effect, whereby there are marked differences in air temperatures between the city centers and the vegetated rural surroundings, as shown in Figure 1 below.
Figure 1 UHI profile in Singapore (Wong and Chen, 2003).
The satellite image in Figure 2 below shows the air temperature differences between man-made areas and vegetated areas in Singapore.
Figure 2 Satellite infrared image of Singapore’s Heat Island effect (Wong and Chen, 2009).
Measurement campaigns are undertaken to understand the significance of the UHI phenomenon. Figure 3 below shows weather measurements being carried out on the roof to capture the ambient weather conditions, and near pedestrian level in the city centre to capture conditions inside street canyons.
Figure 3 The outdoor weather measurement setup on the roof (left) and close to pedestrian level (right).
Pedestrian level measurements are done to understand the thermal environment surrounding the human body, as shown in Figure 4 below. At that level, the biggest heat contribution is from vehicles. Figure 5 shows the impact of vehicles on the air temperature differences between weekends with less vehicular presence and weekdays with more vehicular presence.
Figure 4 Roadside measurement tripod with meteorological sensors to capture pedestrian level conditions.
Figure 5 Average air temperature recorded at 1.5m above ground during weekdays (blue) and weekends (orange) for peak hour period (5:45PM to 6:15PM) for nine sunny days.
Thermal comfort measurements and surveys are also important to understand the impact of environment conditions on humans. Figure 6 shows the typical setup of conducting surveys.
Figure 6 Thermal comfort surveys done with environment measurements on the ground.
The high reflective surfaces of metal and glass can also cause discomfort due to glare. Figure 7 below shows a setup indoors to measure how glare from opposite structures and buildings affect conditions indoors.
Figure 7 Indoor glare measurement setup.
Figure 8 below shows the profile of air temperatures at pedestrian height at the Kent Ridge campus.
Figure 8 Air temperature contour map at pedestrian height at the Kent Ridge campus, with cooler zones in blue and hotter zones in red
Urban ventilation is a passive strategy whereby buildings are designed to allow prevailing wind directions to flow through the site. Figure 9 below shows the North East prevailing wind direction blowing through the Kent Ridge campus.
Figure 9 Wind velocity contour (top) and vector (bottom) of the Kent Ridge campus.
Cool paint on horizontal surfaces is a good strategy to reflect solar radiation back to the atmosphere. Figure 10 shows the application of cool roofs and the comparison of surface temperatures against conventional roofs.
Figure 10 Infrared thermal imaging of conventional and cool roofs.
Greenery is important to minimise solar exposure on man-made surfaces in the urban environment by providing shade and evaporative cooling to lower the immediate air temperature. Figure 11 below shows the impact near a single tree with and without transpiration rate. Volume weighted average air temperature under the tree canopy shows a maximum of 0.8˚C reduction under canopy.
Figure 11 Single tree cooling effect. From the top (Case 1 - no tree scenario), middle (Case 2 - tree without transpiration rate) and bottom (Case 3 - tree with transpiration rate).
Figure 12 below shows the impact of multiple trees in a precinct called Matilda at 2m above ground. The area weighted average air temperature shows a maximum of 1.9˚C reduction.
Figure 12 Multiple trees cooling effect. From the top (Case 4 – precinct with no tree scenario), middle (Case 5 – precinct with trees without transpiration rate) and bottom (Case 6 – precinct with trees with transpiration rate).
In a high density tropical environment like Singapore, reflection of solar radiation via reflective surfaces, such as metal and glass, causes discomfort due to glare and increase in surface temperature of the surroundings. By reflecting solar radiation back to the atmosphere, for instance, using the retro reflective film as shown in Figure 13 below, both heat and discomfort glare can be minimised.
Figure 13 Results of the reflected shortwave (300nm to 2800nm) solar radiation to an upward direction.
Evaporative cooling via misting sprays can help minimise the air temperature around its immediate surroundings. Computational Fluid Dynamics (CFD) simulations are conducted to understand the impact at urban canyon level. For low density areas (Height-to-Width (H/W) ratio ≤ 1.0), a windward wall injection of water droplets provided more effective air cooling at the pedestrian level than a leeward wall injection as shown in Figure 14 below.
Figure 14 The parametric study of dry mist effect on air temperature at Height-to-Width (H/W) ratio of 0.4 and 1.0.
Adaptive thermal comfort suggests that a human connection to the outdoors and control over the immediate environment allow them to adapt to (and even prefer) a wider range of thermal conditions than is generally considered comfortable. Figure 15 shows the rResearch being conducted that enables the quantification of air movement on occupants in mixed-mode ventilated buildings. This research is also in time with increasing interests in hybrid air-conditioning systems, which proposes to achieve energy savings by raising the cooling setpoint. Ceiling fans are then used to offset any discomfort caused by warmer temperature by providing elevated air movement.
Figure 15 Research conducted with Hybrid Cooling Analysis Tool (developed by Mahmoud AbdelRahman and Sicheng Zhan, Ph.D. Students, NUS Department of Building).
With the emergence of the Internet of Things (IoT), it has become cost-effective to implement a digital twin of a building’s operation. A digital twin, as shown in Figure 16, is a digital replica of the actual physical building or system, created through an integration of real-time monitoring and control, advanced energy modelling, and data analytics. The digital twin acts as a bridge between the physical and digital world, providing a platform for advanced analytics to improve building performance and occupant well-being. Examples of its application include:
Figure 16 Creating a digital twin of the building with real-time environmental and occupancy monitoring.
One of the biggest challenges in the evaluation of human satisfaction of the built environment is getting people to interact with the building to provide subjective feedback. Surveys, even online versions, are tedious and impractical for daily use. Research conducted at SDE enables the interaction of occupants with their environments in ways that are useful to them, such as finding and booking a hot-desk space or learning about sustainability features in the buildings on campus. Two smart-phone applications are being launched in SDE to facilitate human-building interaction - SpaceMatch and the SDE4 Learning Trail.
Figure 17 SDE4 Learning Trail – A Human-Building interaction environment for occupants to learn about sustainability features on campus while giving subjective feedback about their comfort.
Figure 18 SpaceMatch - An AI-powered space recommendation application that crowdsources comfort feedback.
Personal comfort preferences can be based on factors such as personality, lifestyle, and physiological-based preferences. Building systems could be much more responsive if they could use these additional preferences in an automated way. Urban design could be influenced by an understanding of the clusters of preferences. Figure 19 shows research that is currently underway to collect data from fixed environmental sensors, various subjective feedback crowdsourcing techniques, and wearable devices to develop a typology of thermal comfort personality profiles.
Figure 19 Thermal comfort personalities are developed using wearable devices that collect physiological and subjective feedback.