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• On-site measurements were conducted to investigate the synergistic cooling effects (SCEs). • The littoral forest yielded more than 3.3 °C cooling effect than that of the separate trees. • The air temperature differences depended strongly on land cover features of each site. • As the LAI of littoral trees decreased 1.0, the average SCE increased by 0.19∼0.31 °C. Both green and blue space are found to be effective for urban heat mitigation and air quality improvement. However, studies on the Synergistic Cooling Effects (SCEs) of green-blue spaces are limited. This paper aims to investigate the SCEs of green-blue spaces in Chongqing, a typical hot humid city in China, through the field measurement and numerical simulation. First, air temperature and relative humidity over different land-use sites (forest, lawn, and impervious pavement) were measured with and without water simultaneously, from July to August 2018. Experimental results revealed the SCEs of green-blue spaces were obvious in 7–12 m surrounding waterfront areas, where the mean air temperature reduction was 3.3 °C higher than the sums of cooling effect of standalone water and forest. Additionally, an ENVI-met model was validated against the measured data before conducting simulation for the study area in five scenarios, including one control group with no trees and four greening cases with different Leaf Area Index (LAI) values to investigate the importance of green infrastructure on the waterfront thermal environment. Simulation results showed that a decrease of 1.0 LAI can lead to a reduction of average air temperature by 0.19–0.31 °C, possibly owing to the enhanced ventilation flow. [ABSTRACT FROM AUTHOR]

• Single image modeling (SIM) method of 3D thermal environment is developed and its accuracy is confirmed. • The flow area distribution of air temperature and wind speed can be calculated. • On-site measurements were also conducted to validate the simulation results. • Simulation results can be used as a guideline in the regional design stage. This paper presents a single image modeling method (SIM) to efficiently identifying the regional thermal environment parameters, which is used to predict and optimize the regional thermal environment and operation in advance. Coupled with the simplified solar radiation solution model, the building complex thermal model is established to predict the temperature distribution of the underlying surface and building surface. Then the heat and mass exchange equations of the horizontal and vertical boundary are simplified and interacted to obtain the flow area air-dry bulb temperature, wind speed, and other information. To validate the proposed SIM method, the method is applied to simulate and analyze the thermal environment in the Huxi Campus in Chongqing, China. The meteorological parameters and building material thermal physical property parameters are used as the initial conditions of the simulations. The simulation results are validated using the summer measurements carried out in Huxi Campus. The results showed that the simulation results were consistent with the measured data. The RMSEs (root-mean-square errors) and MAPEs (mean-absolute-percentage errors) of air temperatures adopting the SIM method were less than 1.65 and 5.00%, and the MAPEs of wind speed was less than 10.00%. [ABSTRACT FROM AUTHOR]

This study presents the experimental measurement of the energy consumption of three top-floor air-conditioned rooms in a typical office building in Chongqing, which is a mountainous city in the hot-summer and cold-winter zone of China, to examine the energy performance of white and sedum-tray garden roofs. The energy consumption of the three rooms was measured from September 2014 to September 2015 by monitoring the energy performance (temperature distributions of the roofs, evaporation, heat fluxes, and energy consumption) and indoor air temperature. The rooms had the same construction and appliances, except that one roof top was black, one was white, and one had a sedum-tray garden roof. This study references the International Performance Measurement and Verification Protocol (IPMVP) to calculate and compare the energy savings of the three kinds of roofs. The results indicate that the energy savings ratios of the rooms with the sedum-tray garden roof and with the white roof were 25.0% and 20.5%, respectively, as compared with the black-roofed room, in the summer; by contrast, the energy savings ratios were −9.9% and −2.7%, respectively, in the winter. Furthermore, Annual conditioning energy savings of white roof (3.9 kWh/m 2 ) were 1.6 times the energy savings for the sedum-tray garden roof. It is evident that white roof is a preferable choice for office buildings in Chongqing. Additionally, The white roof had a reflectance of 0.58 after natural aging owing to the serious air pollution worsened its thermal performance, and the energy savings reduced by 0.033 kWh/m 2 ·d. Evaporation was also identified to have a significant effect on the energy savings of the sedum-tray garden roof. [ABSTRACT FROM AUTHOR]

Increasing envelope facet albedos considerably reduces solar heat gain, thus yielding building cooling energy savings. Few studies have explored the potential benefits of utilizing cool coatings on building envelopes ("cool-coated buildings") based on life-cycle cost analysis. A holistic approach integrating the field testing, building energy simulation, and a 20-year life-cycle-based optimization was developed to explore cool-coated building performance and the maximum net savings of optimal building envelope retrofit and design. Experimental results showed that applying cool coatings to a west wall of an office building in Chongqing, China reduced its exterior surface temperature by up to 9.3 °C in summer. Simulation results showed that in Chongqing, making the roof and walls cool could reduce annual HVAC electricity use by up to 11.9% in old buildings (with poorly insulated envelopes) and up to 5.9% in new buildings. Retrofitting old buildings with a cool roof provided the net savings per modified area with present values up to 42.8 CNY/m2; retrofitting a new building with a cool roof or cool walls was not cost-effective. Optimizing both envelope insulation and envelope albedo can achieve 5.6 times the net savings of optimizing the insulation only, and 1.6 times that of optimizing albedo only. • Potential benefits of cool-coated buildings are comprehensively investigated. • The method integrates field testing, energy simulation and life-cycle-based optimization. • Retrofit and design optimization of cool envelopes are performed based on trade-off options. • The optimal retrofit and design alternatives are presented. • 11.9% and 5.9% annual HVAC energy savings for old and new buildings can be achieved. [ABSTRACT FROM AUTHOR]