In the considered two case studies, performed calculations , simulations and comparison have shown that it is possible to reach an average decrease on the mean air temperature that varies between 0,25 up to 4,5 Celsius degrees, for mainly the summer period and especially the period that corresponds to the highest temperatures. For the simulations executed both for Peristeri and Evripidou area it was considered as a reference day the hottest day of the summer of 2014 (7 of July), which according to the measurements already done by the University of Athens the department of Physics is the period which is more visible the HIE in both areas. The different compactness of the two areas leads to different energy demand and consume, according to previous studies.
By increasing the green areas, changing the surface materials replacing asphalt with pavement tiles more adaptable to a sustainable design, adding water elements, creating more parks and pedestrian streets and plus on the level of building design, adding green roofs and green walls where is applicable and also by creating shadow areas on the rooftop with photovoltaic elements, it can be observed a reduction in the air temperature, the surface temperature and as a result create and ambient with a high level of life quality and improved thermal comfort. This strategy is showing how a huge potential for energy savings lies eventually in the renovation of the existing building stock.
A complete and comprehensive simulation has been performed for both two different urban complexes considered as case studies in the Athens area.
Peristeri urban compound is characterized of an open area with stand alone buildings with the possibility to act with more possibilities in the urban redesign of the area. Possible organization of the parking spaces and creation of the double of the existing green area has shown that the air temperature around the buildings can reach up to 2.5 Celsius degrees which is an important impact. The existence of strong wind coming from the Aegean sea, the actual location of Peristeri as it is in a higher level from the centre and its medium dense urban character allows to have a sufficient decrease of the air temperature during the hot days of the summer even with the minimum basic transformations already mentioned.
On the other hand, Evripidou area that is located in the centre of Athens, it is characterized as a high dense area, with narrow streets, tall building blocks, lack of green and traffic. The existence of wind is rare as the urban complex does not allowed circulation and as a result the quality is poor.
Even if the transformation proposed in order to calculate the possible air temperature change were limited, the results show an adequate decrease. As mentioned earlier there was a reduction around the main block between 0.7 up to 1.5 Celsius degrees.
In total, it can be observed that with basic transformations in different urban compounds and mainly with the existence and the increase of the existing green
It can be observed a reduction in energy consumption that varies between 33% and 31%, showing how a huge potential for energy savings lies in the renovation of the existing building stock.
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DISCUSSION
Nowadays, there is much research being done into ways to better incorporate
landscape as part of urban design, to integrate new forms of green in the buildings. In recent years, very interesting examples of new public landscapes being developed, combined with increased urban density, and new recreational landscapes utilising urban sites have been realized. Theoretically, the increased density of a city should not create limits and restraints and a more sustainable approach could be introduced. (Creation of small urban gardens for recreation and food cultivation, in combination with green roofs water system that could help to collect the rain water for irrigation of the open areas). A very interesting example that has been successfully re-naturalised and turned into Public Park is the park at Port Forum in Barcelona (2006).
It is generally important to ensure and introduce the appearance of new development in tree planting and vegetation. As far the results collected on this chapter the addition of green areas in the urban environment, the use of more natural materials lead to a significant improvement of the microclimate and the outdoor comfort. Innovative ideas of vertical landscaping and the recreation of ground conditions to roof gardens, are now a realistic scenario applied in many cases. Today most cities have established policies on the principle that removal of potential green area at ground level should be offset by planting the equivalent area at roof level. France for example, is one of the few European countries that with a new innovative law have established that all the new structures are forced to have on the terraces or green roof or photovoltaic systems.
Athens, as a particular city, with a complex urban development over the years, as analysed before, is in the need of new measurements to be performed in a first level in the urban redesign and also to the adaptation of the existing buildings and structures to the energy saving demands in European and global scale. Due to its charismatic climate should be a pilot study for all the problematic cities of south Europe and the Mediterranean Area that demonstrate similar climatic data, existence of HIE phenomenon and also have similar urban geometry.
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