If you live in an asphalt jungle in the middle of an urban area, you will surely have heard of the concept of heat island . Urban centers are “ hotter” than the rest of the hinterland, so if you live in the middle of a city you have to resign yourself to the fact that the mercury column in your area will be a few degrees higher than in the suburbs.
The heat island phenomenon has several negative impacts that can be reflected directly and indirectly on human health. The effects of the heat island can be summarized in the following points:
- Increased use of energy to cool rooms in summer (air conditioners, climate control systems, ventilation, etc.)
- Consequent high emission of pollutants and greenhouse gases, including tropospheric ozone
- pollutants transported by urban runoff water and consequent increase in surface water temperatures
Heat Island, the causes
What causes the heat island phenomenon ?
There are two causes and they intensify each other!
#1
In urban centers, solar radiation is absorbed more due to materials such as asphalt and concrete that increase heat accumulation. Due to heavy cementation and lack of green spaces, urban islands lack evaporating/evapotranspiring surfaces.
#2
Use of equipment that releases heat: cars, appliances, air conditioners… anything that uses energy releases heat. If an air conditioner cools your home, the external unit releases heat that increases the phenomenon of the urban heat island .
Heat Island – the solutions
The question becomes more difficult: how can we save ourselves from this mess we have created?
As is clear, the urban heat island is a direct consequence of human activity. Very little could have been enough: to mitigate the heat island effect , it would have been enough to better manage urban spaces. Careful planning of urban centers would have allowed for more green spaces to be maintained in proportion to the cemented surfaces. Unfortunately, human urbanization has always moved and continues to move in the direction of cementing: land consumption is a disconcerting reality that is killing the environment and not only in our country. The advance of cement represents a European problem that requires community directives. Every year, over 1,000 square kilometers of new land are used for human activity and therefore cemented.
The heat island effect is only one of the consequences of the wild concreting, other dramatic implications can be found in the problem of hydrogeological instability, which is strongly felt in Italy .
To slow down the concreting, some contributions have been created to promote the reuse of areas that have already been concreted over but left to decay: in your city, how many abandoned warehouses have you noticed? In this context, tax incentives for the reuse of land have been launched .
Environmental problems rarely have immediate solutions. To mitigate the problem of the heat island in some cities around the world they are looking for materials to replace asphalt. Asphalt is a dark color and therefore has a low reflection coefficient: asphalt absorbs heat. A NASA test is using white roofs to counteract the urban heat island ; white is a reflective color. Even more effective could be the use of green roofs and vegetal walls.
An “improved” version of classic asphalt has already been developed for roads, which is lighter and less prone to absorbing heat. Lightweight asphalt is not harmless to the environment but at least it does not absorb much heat and reflects light better, thus making traffic safer. Bio asphalt (bioasphalt) made with nano materials of organic origin has a lower impact but its high production costs still make it prohibitive.
To get an idea of the gap between green space and asphalt, just think that a square meter of asphalt surface absorbs 6 times more thermal energy than the same surface of lawn. If you are interested in combating the heat island phenomenon (very much felt in the cities of Bologna, Milan, Trento, Ancona, Turin …) you can establish, in your small way, a movement to support the installation of green roofs and to increase green spaces in the city. If you intend to start from your home, here is a guide on how to create a green roof . Do not exclude the possibility of organizing an urban garden or proposing to the administration of your municipality of residence, the use of intelligent urban furnishings such as the Tillandsia plant .
