Green Roofs as strategy to mitigate city problems (Part 1)

In the 21^st Century, the human species have chosen cities as the dominant place to live. In 2008 it was the first time in history of human kind that urban population equalled rural population. By 2050, urban population is expected to be the 70% of the total. This data means that nowadays almost 4 billion people live in cities and by 2050 will reach 6’5 billion. (Source: United Nations “World Urbanization Prospects: The 2007 Revision)

Giving the number of issues most world cities present, and knowing that they will continue to increase in size, it is essential to research and work on possible strategies to mitigate city problems. 

The use and promotion of green roofs right now is essentially focused on the mitigation of two mayor city challenges: Heat urban effect and water storm effect.

Heat Island Effect is essentially the result of an increasing of temperature within the city area due to the high mass paving and the buildings covering the natural soil. Recent studies done by the US Environmental Protection Agency (EPA, 2008) show that the temperature of urban areas rises up directly proportional to the number of people that live in them.

When choosing materials to cover the urban grid and to rise up its buildings, human have created a very extended impervious surface that act as radiators absorbing sun heat during the day and radiating it at night. Nowadays with climate change and the increase of the world’s temperature, urban heat island effect is becoming so much more prominent and intense. It causes in humans a high level of thermal discomfort and is directly proportional to the increase in the usage of Air Conditioning systems in the cities.

Green Roofs are presented as one the best solutions to mitigate Heat Island Effects. They provide a pervious surface that traps the heat and thanks to their evapotranspiration they cool up the air.

The design and installation of a green roof, must be done by a professional who would recommend what type of green roof to use, extensive, semi-extensive or intensive, what type of plants to use (better native adaptive species) and what are the extra needs for it to work properly. Normally in a cold climate, it is necessary to install insulation panel in addition to the green roof. And in hot and dry climates, it is necessary to intall irrigation system that can collect water from the rain.

If every city in the world had this ancient technique, which romantically means that you return the stolen soil to the Earth after placing a building over it, the temperature peaks would be more moderate reducing the cooling loads during summer, and the heat island effect would not be the big problem it is now.

Green Roofs are worth it. 

Review the climate chart with green systems benefits and conditions that GUASL has prepared after doing an extensive research on how well Green Roofs perform in different climates to make sure you know what you will get depending on your region.