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Atlanta is a scorching heat island, but can green roofs help?

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A Q&A with local pros about the pricier—but potentially effective—green-roof alternative

Thermal imagery from urban Atlanta in the year 2000, when the city’s “heat island” issues were reportedly at their worst.
Thermal imagery from urban Atlanta in the year 2000, when the city’s “heat island” issues were reportedly at their worst.

It’s midsummer, which means that perennial, suffocating, climatological sauna has befallen Atlanta.

Like most urban places, Atlanta’s status as a heat island is hardly surprising, what with all the heat-capturing concrete and carbon emissions, which spell hotter summer temps intown (2.4 degrees in the daytime, about 4 degrees at night) than surrounding rural areas.

What’s more surprising: The ATL’s heat-island problem is actually getting better.

That’s the word from Bill Lomel, Sentry Roof Services president, whose company has worked with Hartsfield-Jackson International Airport and other major clients to implement green-roof practices that include reflective roof materials and energy-effecient insulation.

An image from around 2000, when metro Atlanta’s heat islands reached a peak.

The result, per Lomel, is that Atlanta’s heat island footprint has been dramatically reduced in the past decade, as buildings implementing “cool roofs” throughout town are saving up to 20 percent in energy costs. Meanwhile, the tops of such buildings are more than a third cooler than standard roofs, which can reach July temperatures of a blazing 150 degrees.

Atlanta leaders have recently gotten serious about powering the whole city with nothing but sustainable energy by 2035, and Lomel points to anecdotal success stories where the cooler, green-roof trend is catching on: NCR’s new global headquarters in Midtown, the High Museum, Georgia World Congress Center, SPANX headquarters in Buckhead, Ponce City Market, and Atlanta City Hall, where Lomel says a vegetative roof has slashed energy usage by 25 percent since 2008.

That’s the good news (although this town, obviously, still boils). But what might the future hold?

We caught up with Lomel and Stella Mathews, Atlantic Star Design landscape architect, for an email Q&A on the subject:

Curbed Atlanta: What unique advantages does Atlanta offer when it comes to implementing sustainable or green roofs?

Lomel: Atlanta is truly a city in the forest surrounded by vast stretches of greenery and landscaping and intermixed in the city’s Midtown and downtown areas. As a city, we have invested a lot in our green, urban areas, which will help lay a perfect foundation for Atlanta to begin taking the next steps in implementing green roofs on office towers, residential buildings, and industrial structures.

Our local government has placed a high value on advancing green and sustainable building practices for the city’s future, positioning Atlanta closer to the forefront of the green roof trend.

NASA imagery from 2000 showing the relationship between non-vegetated areas of Atlanta and urban heat.

Mathews: Atlanta is already made up of heavy-duty existing and planned structures that can be utilized to create a positive impact on the environment and economy. The city can transform these residential and commercial structures to create unique, private green spaces that will bring wildlife to the city’s core and add a biodiverse element to the heart of Atlanta, which is unseen in major cities across the United States.

What about unique challenges?

Lomel: It’s no secret Atlanta’s climate can reach both extremes, from scorching hot summers with 100 percent humidity to below-freezing winters, which presents an interesting challenge. Atlanta is also a cost-driven market that will likely have concerns about the large costs of the implementation and maintenance of green roofs.

Can you give an idea of what these costs?

Mathews: Green, vegetative roofs typically cost two to three times as much as a standard roofing system. The cost is affected by the maintenance of the roof, the design of the components, and the landscaping used.

But, the benefits of a vegetative roof greatly outweigh the costs. Vegetative, green roofs can improve stormwater management and reduce the temperature of the roof, allowing the system to last longer and work more efficiently. Green roofs are also a major value-add to any building.

Research shows that resident turnover is lower in residential buildings that offer personal green spaces and amenities to residents. Green roofs can also have a positive effect on people’s productivity and mental wellness. Research shows that professionals that can see green space from their office windows are more productive than those who cannot. Green roofs can also speed up the recovery process for patients at hospitals or healthcare facilities.

Can you explain the actual materials used? Is this typically a living roof with grasses and even edible vegetation?

Lomel: The foundation of a green roof is the waterproofing and that is basically a standard commercial roof. We typically use 60-mil thick membrane that can withstand wear and tear.

Mathews: After the foundation of the roof system is placed, a proper drainage system is installed that consists of several drainage boards and aeration components to avoid water pooling. Engineered soil is often used on vegetative roofs to help with the weekly or annual maintenance of the vegetative roof system. Any species of plant can be placed on the roof, as long as the roof is properly designed and maintained.

Vegetative roofs can also be used in tandem with solar panels. The plants and vegetation work to increase the efficiency of the solar panels, allowing the system to provide benefits for the building.

Are there particular areas of the city that are poised to be improved?

Lomel: Industrial parks in Atlanta can implement green roof practices to offer a unique value-add to tenants and decrease development costs and improve the industrial park’s environmental footprint. Residential and commercial buildings are also ready for sustainable roof practices.

How much more of a difference can Atlanta make by addressing its roofs?

Lomel: Implementing these sustainable, green roofs will have a positive impact on the environment and save the city money. These practices will increase the efficiency of your roofing system, resulting in better performance and a longer lifespan for your roof.