Heat Island Effect - How To Minimize It
Reducing Your Heat Island Effect Can Significantly Affect The Environment & Your Microclimate
The heat island effect refers to the amount of heat a surface radiates during the sunlight hours of the day.
Why is heat island effect bad for our environment?
The buildup of radiated heat adds to the total heating and greenhouse effect of our planet. The annual mean air temperature of a city with 1 million people or more can be 1.8 degrees F to 5.4 degrees F warmer than it's surrounding rural areas and can be as high as 22 degrees F higher in the evening and on a clear night.
Another example of heat island effect: On a hot summer day, try to walk barefoot on asphalt pavement, especially pavement only a few years old. You can't, at least I can't. Now walk on a light concrete surface exposed to the same sun. It is only warm to the touch. Think of the difference in heat radiated from these 2 different surfaces and you start to realize the heat island effect.
By reducing heat island effect we can lower energy costs, reduce our dependence on fossil fuels and reduce air pollution. Also higher air temperatures promote the formation of ground-level ozone.
Also, increased heating along with higher level of pollution can contribute to general discomfort, respiratory difficulties, heat cramps,exhaustion, nonfatal heat stroke and other heat-related mortality.
And yes, all the little things that we can do to control our own micro-climate can help greatly.
To Reduce Heat Island - Shade Pavements
There are several solutions and we will look at each of them carefully:
Install light and highly reflective roofing materials.
Live Roofs Cool Your Structure
Small Homes Can Seem Large
A live vegetative roof benefits your home in several ways. It reduces the heat island of the living space below by absorbing the suns rays and insulates at the same time. This process is called evapotranspiration. On a hot day a green roof can be cooler than the surrounding air temperature, whereas a normal roof can be upwards of 90 degrees F.
Secondly it slows down or delays a storm water event. This is important because as the roof absorbs some of the water and slows down the flow of the storm, it impacts the flash-flooding aspect of a storm. When an area on your home site has no ability to absorb any water it is called impervious. Items that fall into this category are concrete and asphalt drives, roofs and patios.
Roofing That Is Reflective Sheds Heat
Many manufacturers have been improving the performance of their roofing products over the past few years. Others are now publishing data that relates to the reflectance facts their roofs exhibit.
One of the easiest characteristics to look for when searching for roof materials to reduce the heat island effect, is an Energy Star Label for that roof. Roofs meeting the Energy Star program of the EPA and DOE help consumers identify the most energy-efficient roof materials.
Heating characteristics of a roof are based on 2 properties. These properties are solar reflectance or "albedo", which is the most import factor, determines how much of the sun's heat will be reflected away from the roof. Albedo can be from 0, which means it absorbs all the sun's radiation to 1.0 which represents total reflectivity.
Low-slope roofs < 2:12 should have an albedo of 0.65 or higher.
Sloped Roofs > 2:12 should have an albedo of 0.25 or higher.
The second characteristic is emittance which also plays a role, especially in warm climates. The emittance of a material refers to its ability to release absorbed heat. This can vary from 0% to 100%. Look for roofing materials that exceed 85% emittance.
Cool roofs do deflect some desired heat in the winter, though the net energy savings in the summer easily makes up for this.
Install or Replace Your Pavements With Cool Pavements
Traditional asphalt pavements can reach temperatures upward of 150
degrees F in the summer.
If your prevailing breezes blow over this super-heated surface, toward your home, that extremely warm air heats up your home and it's occupants. Also this air is radiated into the atmosphere adding to greenhouse gasses, air pollution and overall planet heating.
Cool pavement can be created with cool pavement technology for both concrete and asphalt, as well as newer technologies such as coatings to apply over existing pavements and grass paving.
If your are planning on the replacement or installation of a new driveway, consider a concrete drive with an added whitening agent to provide the greatest reflectivity possible for your new pavement.
Another desirable aspect of concrete pavement is the lack of petroleum in the product whereas asphalts have a high petroleum content. The recycle content of asphalts is increasing dynamically though so the actual impact on our natural resource is being reduces as time passes.
If you are interested in more information of cool pavements click HERE for a PDF from the EPA.
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