The climate in cities differs significantly from those found in the surrounding area. These differences results from modifications of the Earth's surface that alters the disposition of "natural energy balance" at a micro-scale and the concentration of activities that results in anthropogenic emissions that change the composition of the atmosphere. These urban effects have distinctive temporal and spatial properties with different impacts on building energy performance depending on their purpose, which are rarely accounted for. This paper examines performance implications of a change-of-use (from office to residential) in the context of the UK government's proposal to encourage regeneration and to meet housing needs. However , the diurnal occupation and activity patterns of these uses are distinct. For office buildings, with daytime occupation, focus is on the diurnal heating cycle driven by solar energy gains to which internal energy sources must be added. For residential buildings occupation and activity are primarily associated with the diurnal cooling period, and lower levels of activity that results in a primary heating need. This paper highlights the link between the timing of the urban climate effects, the urban setting and energy performance in a typical city street, where buildings are currently designed for commercial use. It employs London's current and projected climate to simulate heating and cooling demands. By studying the role of urban form and its implications on the suitability of a buildings function we find that a 'form first' approach should be considered in the early design stages over the standard 'fabric first' approach.

One of the tenets of urban sustainability is that more compact urban forms that are more densely occupied are more efficient in their overall use of space and of energy. In many designs this has been translates into high-rise buildings with a focus on energy management at their outer envelopes. However, pursuing this building focused approach alone means that buildings are treated as standalone entities with minimal consideration to their impact on the surrounding urban landscape and vice versa. Where urban density is high, individual buildings interact with each other, reducing access to sunshine and daylight, obstructing airflow and raising outdoor air temperature. If/when each building pursues its own sustainability agenda without regard to its urban context, the result will diminish the natural energy resources available to nearby buildings and worsen the outdoor environment generally. This paper examines some of these urban impacts using examples from the City of London where rapid transformation is taking place as very tall buildings with exceptional energy credentials are being inserted into a low-rise city without a plan for the overall impact of urban form. The focus of the paper is on access to sunshine and wind and the wider implications of sustainable strategies that that focuses on individual buildings to the exclusion of the surrounding urban landscape. The work highlights the need for a framework that accounts for the synergistic outcomes that result from the mutual interactions of buildings in urban spaces.

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Regulated energy loads of buildings are typically explored at the scale of individual buildings, often in isolated (and idealised) circumstances. By comparison, there is little research into the performance of building groups that accounts for the interactions between buildings. Consequently, the energy efficiency (or penalty) of different urban configurations (such as a city street) are overlooked. The research presented here examines the energy demand of a city street in London, which is comprised of typical office buildings with internal energy gains associated with a daytime occupancy. Simulations are performed for office buildings placed in urban canyons that are defined by ratio of building height (H) to street width (W). The results show the annual energy demand is dominated by the cooling load, which can be significantly reduced through street design that provides shading by increasing the H/W value. However, the 'best' street design for modern office buildings may be incompatible with that for residences or, for that matter, outdoor climates.

Ti t l e D e si g n s u m m e r ye a r w e a t h e r-o u t d o o r w a r m t h r a n ki n g m e t ri c s a n d t h ei r n u m e ri c al ve rific a tio n