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The cooling effect in a courtyard's garden and in the adjoining ground- and first floor verandas, attached to the NNE side of a two-storey building is evaluated with measurements performed during a hot weather summer period in Athens. Results revealed a well defined and strong daytime cool island between the buildings rear garden (with about 85% canopy covering) and an air temperature reduction for the ground floor veranda, as compared with an urban square with low canopy coverage (about 15%), reaching a maximum air temperature reduction of 6.5 K during daytime. Compared with a nearby densely wooded park, the garden and the veranda were found 1–1.5 K cooler during 4 and 8 hours during daytime, respectively. Using the physiologically equivalent temperature thermal index with appropriate adjustments to local conditions, it was found that those two sites, compared with the urban square, were able to mitigate the extreme thermal stress conditions and to decrease the daily number of hours associated with strong thermal stress conditions. It is concluded that appropriately designed semi-open spaces in residential buildings, well known from vernacular architecture for their qualitative benefits, may be considered as positive bioclimatic pedestrian transitional elements in sustainable urban design for Mediterranean climates.
Tsiros et al. (2013) studied this question.