When was the last time you cycled out the city after dark? Once you left the buildings behind did you become aware of just how the temperature range lowered? Particularly evident in the evening, if there is very little breeze, you instantly recognize the particular way our built up landscape creates as well as stores warmth that's then discharged.
There is a name just for it: the Urban Heat Island Effect.
When the concrete and bricks of houses in the area plus the asphalt of streets have replaced the permeable vegetation layers of the natural surroundings then it forms an urban heat island.
The ability of an urban area to gather and collect heat in this way was initially noticed by a British meteorologist, Luke Howard, in the early 1800's. Since the 1800, buildings have grown larger and towns have spread out claiming more green land. As well as buildings growing in quantities and scale, now we have introduced far more technology, from cars to air-conditioning, which pumps additional heat in to the places where we reside.
Satellite technology now allows us to gauge far more successfully the temperatures of our urban and rural areas. The final results reveal that the natural landscape is cooler than the 'islands' that we have designed. The need for increased cooling because of the increase in temperature creates higher energy consumption and additional air pollution. Additional pollution and increased temperature ranges affect the health and wellness of people who live and work there, and help to make towns and cities less pleasant areas to reside in.
Stormwater is warmed as it runs off the non-porous surfaces of buildings and streets and when it's released into streams, can harm fragile ecosystems. Often the rainfall alone can result in issues so that designers and urban planners need to develop complex systems to channel it faraway from population centres. These are generally overloaded when rainwater combines with sewage and results in increased health concerns and damage to ecosystems.
The numbers of people living in a city are climbing each and every year with somewhere around 50 percent the world's population already living in a city. Seeing that we can't adjust where many people are living, urban organizers try to look for techniques for creating the usable living space healthier and more energy-efficient.
A large proportion of virtually any city's surface area is made up of rooftops. They signify an important factor within the heat island challenge but most likely since they're mostly out of eyesight, they sometimes are overlooked. The speed at which a physical object can reflect radiation from the sun is known as its 'albedo'. Surfaces within a city which have a reduced albedo tend to be not as effective because they do not reflect radiation away from the surface and thus assist in keeping structures warmer.
Common asphalt built-up roofs have got a modest albedo, reflecting just about 26% of the sun's radiation. The rest of the solar radiation is soaked up and produces heat that remains in the area if you have little or no wind.
An eco-friendly roof top however, which has a increased albedo, reflects a lot of the sun's radiation from the structure. It keeps the building beneath it cooler as it supplies shade and heat insulation. The vegetative layer keeps rainwater, instead of basically warming it and transporting it away. The evaporation of water from the substrate and transpiration of wetness from the vegetation acts to cool the rooftop and prevent it from becoming another supply of urban heat.
It's crystal clear that upgrading normal roofs with flat roofing products that are cooler can play an important role in offsetting the undesirable influence of the urban heat island.