The contribution of bioclimatic architecture in the improvement of outdoor urban spaces - Solar Energy Sciences and Engineering Applications - page 637

◦ Use of large-size trees to enhance shading and evapotranspiration in the

considered area;

◦ Use of light-coloured materials to decrease the absorption of solar radiation;

◦ Reduction of anthropogenic heat from traffic;

Maximum possible use of environmental heat sinks and in particular of the
ground to offer low-temperature fresh air.
The reduction of the ambient temperature achieved was up to 3 ◦ C, while the
surface temperature reduction was 6-8 ◦ C.

◦

• Improvement of microclimatic conditions of a square in the centre of Athens

(Greece) was studied by Gaitani et al. (2011). The area's environmental param-
eters were initially monitored, and surface and air temperature, wind speed and
direction, humidity and pollution levels were measured. Based on CFD model
analysis the following conclusions were made: (i) lack of spatial homogeneity of
the air temperature; (ii) increase in surface temperatures due to highly absorbing
materials; (iii) high wind speeds in specific areas of the region under study; (iv)
high concentration of particulate matter. Through a series of interventions, such
as increased greenery, installation of cool materials, increased shading and use
of earth-to-air heat exchangers, the area's comfort conditions were significantly
improved.

• An assessment of wind flow in the urban area of Dubai (United Arab Emirates)

and its contribution to passive cooling was performed by Al-Sallal et al. (2012).
The overall assessment was based on CFD analysis of laminar and turbulent flow
in the specific region. The study revealed the importance of street design for the
bioclimatic urban design. In the case study, the wind speed during the laminar
analysis showed that it was within comfort levels in the pedestrian area. Turbulent
wind flow was channelled by the street canyons and increased in various areas,
contributing to an improvement in thermal comfort sensation. Analysis showed
that passive cooling through natural ventilation can be effective in providing com-
fort for 25%, 26% and 27% of the year with wind speeds of 1.5, 3 and 6 m/s
respectively. Moreover, wind speed contributed to comfort when the aspect ratio
of the canyons was 1.75.

• The contribution of vegetation in urban structures was evaluated by Picot (2004)

for Piazza della Scienza in Milan (Italy). A set of field measurements, including
air and radiant temperature, wind velocity and relative humidity, were taken,
followed by an evaluation of thermal comfort coupled with a vegetation growth
hypothesis. A series of simulations were performed, taking into consideration
different vegetation growth scenarios without changing the site configuration. The
screening potential of tree foliage on the reduction of solar radiation was also
considered. The analysis showed that the presence of vegetation can reduce the
heat budget of a human body by 50-150/m 2 depending on the type of vegetation
and foliage.

• The influence of evaporative towers in the outdoor comfort levels for Madrid

(Spain) was studied by Soutullo et al. (2011). An experimental campaign was
carried out to analyse the thermal influence of the specific towers by installing
a series of wind, temperature and humidity sensors in different positions and at
different heights. At the pedestrian level a temperature reduction of almost 3.5 ◦ C
and a cooling efficiency of about 32% was revealed.