Developing a performance-based 3D green-blue index for sustainable urban living (14617220) (1 Dec 20 - 30 Nov 23)
• Researchers: NG Yan Yung, JIM Chi Yung
• Funding Amount: HK$1,168,207
• Funding source: Research Grants Council - General Research Fund

Urban overheating is a foremost environmental challenge facing tropical cities including Hong Kong, and results in several health impacts including heat stress and discomfort leading to illness and death (Kjellstrom, Holmer, & Lemke, 2009). One verified solution is the innovative integration of greenery and waterbodies into city design. Based on our previous study (Ng 2012), 20 – 30% of the gross floor area is allotted for greening particularly to mitigate the heat island effect. This greenery coverage was based on ~1C temperature regulation and derived from ground-level tree planting numerical experimentation. However, when implemented, the government practice note included façade and rooftop greening, and waterbodies with variable reduction factor from 0 - 50% to allow practical flexibility. However, these variant combinations have no empirical evidence to ascertain equal thermal regulation performance. To fill this knowledge gap, this study will develop a new performance-based green-blue
infrastructure index for urban overheating mitigation by conducting very-highresolution microclimate analysis of the impact of different combinations of proportions of green-blue infrastructure coverage relative to the total surface area in the highdensity context.

The objectives are to:
(1) Conduct field measurements of bio-meteorological variables at 12 realistic sites where green-blue infrastructures interfaced with the built-environment using coupled Human Biometeorological monitoring Systems (HuBioSys) to have a better understanding of the impact of their cooling effect and human comfort improvement, and to provide a basis to calibrate and validate the model to be used for objective 2;
(2) 768 sets of parametric models composed of varying urban morphological parameters and realistic/practical green-blue infrastructure coverage options will be numerically tested for their heat mitigation performance in the prevailing hot-humid weather conditions. The obtained understanding will be used for objective 3;
(3) Develop a new performance-based green-blue infrastructure index using multivariate regression modelling which will be proposed as a new tool for climate-sensitive urban planning and design; and
(4) Using the index, sensitivity test will be conducted on realistic sites and scientifically proven green-blue implementation strategies that could be used to modify the greening aspects of the Sustainable Building Design (APP-152) and Hong Kong Planning Standards and Guidelines (HKPSG) chapter 4 will be drawn.

In conclusion, this study will respond to the need for a new “green index” for liveable high-density city proposed in the Hong Kong Government’s “Hong Kong 2030+” by providing the first green-blue infrastructure index that is transferable to other highdensity cities in the region e.g. Singapore.