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The study looks at the potential of physical characteristics in mitigating the Urban Heat Island Intensity (UHI) in London during summer. This research uses six on-site variables namely aspect ratio, surface albedo, plan density ratio, green density ratio, fabric density ratio and thermal mass for the investigation in six data sets. The climatic variations in summer are controlled by classifying the data into clear sky, partially cloudy and cloudy periods. Geographical variation is controlled by classifying the data into core, urban and semi urban areas. Maximum daytime UHI of 8.9 º C is found in semi-urban area during partially cloudy period while maximum nocturnal UHI of 8.6 º C is found in urban area during clear sky period when the wind velocity is below 5 m/s. The most critical climate and geographical location in determining the changes in outdoor air temperature in London are partially cloudy periods and urban areas respectively. Among the variables studied, most critical 2 variable that determines the daytime and nocturnal changes in outdoor air temperature is surface albedo.

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The urban heat island (UHI) is a well-known effect of urbanisation and is particularly important in world megacities. Overheating in such cities is expected to be exacerbated in the future as a result of further urban growth and climate change. Demonstrating and quantifying the impact of individual design interventions on the UHI is currently difficult using available software tools. The tools developed in the LUCID ('The Development of a Local Urban Climate Model and its Application to the Intelligent Design of Cities') research project will enable the related impacts to be better understood, quantified and addressed. This article summarises the relevant literature and reports on the ongoing work of the project. Practical applications: There is a complex relationship between built form, urban processes, local temperature, comfort, energy use and health. The UHI effect is significant and there is a growing recognition of this issue. Developers and planners are seeking advice on design decisions at a variety of scales based on scientifically robust, quantitative methods. The LUCID project has thus developed a series of tools that (1) quantify the effect of urbanisation processes on local environmental conditions, and (2) quantify the impact of such conditions on comfort, energy use and health. The use of such tools is vital, both to inform policy but also to be able to demonstrate compliance with it.

One of the primary reasons for the application of cool materials is their energy and associated environmental impact on the built environment. Cool materials are usually applied on the roof of buildings to reduce cooling energy demand. The relative benefits of this reduction depend on the construction of the building, external weather conditions and use of the building. This paper examines the impact from the application of a reflective paint on a flat roof in a naturally ventilated office building in the area of London, UK where the climate is moderate with high heating demand by buildings.The environmental conditions (internal/external air and surface temperatures) of the building were monitored before and after the application of the cool roof during the summer. It was found that internal temperatures were reduced after the application of the cool roof. The building was modelled using TRNSYS and the model was calibrated successfully using the measurements. A parametric analysis was carried out by varying the reflectivity and insulation of the roof and ventilation rate; the heating and cooling demand for a year was calculated using the Summer Design Year for London as the weather file. It was found that cooling demand is significantly reduced, heating demand is increased and the total energy savings vary between 1 and 8.5% relative to an albedo of 0.1 for the same conditions. In free floating (naturally ventilated) buildings summer comfort is improved but there is a penalty of increased heating energy during the winter. Thermal comfort can be improved by an average of 2.5 o C (operative temperature difference for a change of 0.5 in albedo) but heating demand could be increased by 10% for a ventilation rate of 2 air changes per hour. The results indicate that in the case of temperate climates the type, operation and thermal characteristics of the building should be considered carefully to determine potential benefits of the application of cool roof technology. For the examined case-study, it was found that a roof reflecticity of 0.6-0.7 is the 2 optimum value to achieve energy savings in a cooled office, improve summer internal thermal conditions in a non-cooled office (albeit with some heating energy penalty). It indicates that it is a suitable strategy for refurbishment of existing offices to improve energy efficiency or internal environmental conditions in the summer and should be considered in the design of new offices together with other passive energy efficient strategies.