The Heat Island Effect Makes Urban Cities Hot

Wed, 2012-11-14 10:14

Last Updated: 2017-09-11 02:45

This summer’s scorching heat, record temperatures, and devastating drought have certainly spurred more conversation about climate change, global warming, and the need for energy conservation. The need for change is especially evident in our cities where a large percentage of energy consumption is concentrated and where the heat island effect is causing temperatures to climb even higher.

The Heat Island Effect

The heat island effect is the increase in urban temperatures as a result of the sun’s energy being absorbed by the impervious surfaces that abound in cities. Concrete, brick, asphalt, and other dark surfaces absorb the energy of the sun during the day and store it. As a result, temperatures remain higher for a longer period of time, the city consumes more energy for cooling, and greenhouse gas emissions increase.

The heat island effect is nothing new to green building specialists and researchers who have been hard at work finding solutions. The LEED rating system has addressed the issue through credits that award points for measures aimed at reducing the heat island effect. As more cities set out to reduce energy consumption and carbon emissions, the heat island effect is demanding attention, from the top down.

Green Roofs

rooftop gardenGreen roofs don’t just look pretty; they come with a long list of benefits for the environment, city management, city dwellers, building owners, and occupants. Rooftop plantings provide a protective membrane that increases the life of the rooftop and adds an extra layer of insulation. Through evapotranspiration, vegetation cools the roof and helps filter contaminants out of the air. Cities and our ecosystems benefit further from enhanced stormwater and water quality management provided by green roofs. Vegetated rooftops have even been found to improve the production of solar PV panels by helping to keep the panels at a cooler, more optimal temperature. Rooftop gardens may also provide peaceful open space for city dwellers to escape the busy hustle of the city below and may even yield fresh produce.

Cool Roofs

Cool roofs are an alternative solution to green roofs when installation of vegetative cover is cost prohibitive or when the roof is not engineered to handle the load requirements of a garden. A cool roof is coated in a highly reflective material that is designed to reflect the sun’s energy, rather than transferring heat back to the building and surrounding air. In order to achieve the desired level of performance, the material must have high solar reflectance and high emissivity qualities.

Increasing Trend

According to the 2012 Annual Industry Survey of Corporate Members conducted by Green Roofs for Healthier Cities (GRHC), the green roof industry grew by 115% in 2011. Chicago remains the leader with the most square footage of green roofs installed, followed closely by Washington, DC and New York City.

Chicago’s City Hall is home to a rooftop garden that is a living laboratory to study the green roof’s effects on heating and cooling benefits, success rates of different plant types, and water run-off rates.

In Washington, DC, Mayor Vince Gray recently released a 20-year sustainability plan that includes a goal of installing another 1.5 million square feet of green roofs.

The city of New York has established its own NYC Cool Roofs program to promote the application of reflective surfaces on rooftops to cut energy usage and lower greenhouse gas emissions. New York also implemented a one-year tax abatement to support the installation of green roofs, and Brooklyn is set to serve as host to the nation’s largest rooftop garden.

The green building industry remains at the forefront of efforts to green our cities. Do you want to learn more about the LEED rating system and how it contributes to energy efficiency and pollution control through the built environment? To find out more about LEED accreditation, visit Everblue’s LEED Training programs.

photo credit: Pro-Zak via photopin cc

By Amy Malloy

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