Research on ecological design to enhance comfort in open spaces of a city (Valencia, Spain). Utility of the physiological equivalent temperature (PET)

For many years now, research has focused on issues concerning making cities easier to live in and some of the most important of these concern climatology and thermal comfort issues. There is also a growing awareness of the importance of open spaces and green areas, as key elements in providing opportunities for human interaction, leisure and physical exercise. They are important for all inhabitants, but particularly so for children and the elderly population. Of especial interest are the studies which have examined the interaction of comfort with the urban climate. This issue was studied throughout the twentieth century, but recently the role which can be played by biometeorological indices has come to be recognized, especially because of the better understanding them for those responsible for the design of these urban spaces. This study explores the application of the PET index to urban micro-spaces (urban structures), where general values for cities are not valid and where there is a need to know the PET values in order to measure the impact of all items of the urban environment which can provide an increase in comfort. The study was carried out in Valencia (Spain) with the aim of discovering, through these indices, the natural and ecological effects of urban design which can improve comfort. The study focused on: the role of water features, streets with and without trees, squares with hard and soft street surfaces, the effect of different street orientations and the impact of breezes on the city. We have found that the sheets of water, or ponds, provide a cooling effect for the space in which they are located because they have a lower albedo than its surrounding area. In narrow streets, the trees may have a blanket effect and prevent the passage of breezes. Water jets of the fountains should be designed to take advantage of the effect of the breeze to improve the thermal comfort in the surrounding area. The use of hard surfaces and light colors causes a great thermal stress in summer due to higher solar reflexivity that involves higher heat load.