The focus of this dissertation is the urban roofscape of Athens and aims to identify the variables, as well as to explore the potentials that are associated with the sustainable regeneration of this particular layer of the urban configuration. The investigation of the prevailing types and spatial characteristics of this layer will identify the variables affecting the environmental behaviour of the urban rooftops and whose assessment, through microclimatic simulations and literature review, will establish the layout of possible interventions; the outcome of this research is related with the specific climatic context and the factors that define the perception of outdoor comfort. Finally, these environmental factors will formulate the design proposal for an urban rooftop in the centre of Athens.

The research deals with the impact of urban form and vegetation on the microclimate and consequently, outdoor thermal comfort and energy consumption for the residential sector in New Delhi (28° 35′ N, 77° 12′ E). A representative form for the region- The Urban Street Canyon is studied and the variables evaluated are orientation, aspect ratio (H/W), façade projections and the addition of vegetation. Performance indicators for assessment are established through literature review, namely, air temperature, mean radiant temperature and wall surface temperature. The investigation is carried out using fieldwork measurements as a starting point and then in detail, through analytic work. The three dimensional numerical model ENVI-Met (v.3.1), which simulates the microclimatic changes in the urban environment in a high spatial and temporal resolution is used as the tool for analysis.

Symmetrical urban canyons oriented N-S and E-W with aspect ratios ranging from 0.5 to 4 were tested on a typical summer day in June. Air temperature proved to be sensitive to variation in aspect ratio, decreasing with an increase in aspect ratio, the maximum difference being of the order of 1K. Mean radiant temperatures experienced by a person showed a direct link to the exposure to solar radiation, with shading resulting in a lowering in temperature by 15-35K. Wall surface temperatures were strongly affected by the aspect ratio in the case of N-S streets, while the E-W orientation limited the effectiveness of the walls in shading the canyon surfaces as the sun movement is parallel to the street.

Shading by two types of tree canopies – light and dense was tested. A dense tree canopy covering the entire street lowered air temperatures by about 2K. Both canopies showed benefit for lowering mean radiant temperatures and wall surface temperature, especially for E-W streets where the duration and area of exposure is high.