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What Are Green Roofs?

And why are so many of them showing up on commercial buildings?

So much of the news these days concerns the color green. We’ve all heard the phrase “going green” enough times that it’s now firmly entrenched in our lexicon. And while usually green is meant figuratively as shorthand for sustainability or environmental concerns, in some cases it is being used literally. In recent years, green roofs have become popular, and they are actually green because they are essentially rooftop lawns or gardens. Because this type of roof helps with energy efficiency, they are starting to pop up on many commercial buildings.

How does a green roof work?

Planting bushes or flowers on your lawn is easy because you’re starting with a layer of dirt. When your base is concrete or asphalt, this becomes a much bigger challenge. Therefore, a green roof has to be constructed properly to be successful, and this involves building these layers:

  • Membrane: A green roof has to start with a good membrane, as this separates the roof from the structural supports. Because a green roof needs a lot of water, the membrane has to prevent it from leaking through, and it also has to be strong enough for the extra water weight. In order to avoid deterioration, a membrane needs a protective layer, and this can be comprised of copper foil, thick plastic, or other suitable materials.
  • Insulation: On top of the membrane needs to be a layer of insulation, which protects the membrane.
  • Drainage: The drainage layer works to remove any excess water. A good drainage system for a green roof is designed to allow plant life to use stormwater for a long period without causing oversaturation of the entire roof.
  • Root barrier: The root barrier is another essential component of a green roof because it stops roots from getting to the membrane and puncturing holes in it, which could lead to leaks.
  • Growing medium: The growing medium is what the vegetation will grow out of. Choosing the right type and mixture will depend on which types of plants will be used.
  • Vegetation: The top layer of a green roof is the green stuff itself, and what exactly this is should correspond to the climate and the building’s condition. Flat roofs should be able to support tall and heavy vegetation, while slanted roofs are better suited for plants that are lighter and shorter.

What are the benefits of a green roof?

There are several reasons why a green roof is good for the environment as well as building owners, including:

Reduced energy usage

A green roof supplies a building with shade, and it also creates evapotranspiration. This happens when the plants absorb water and then use heat in the air to evaporate the water. The result is a much cooler building. Green roofs are especially useful in cities because they counter what’s referred to as the Urban Heat Island Effect. With so many dark roof surfaces in urban settings, this causes the temperature to go up, and this leads to more air conditioning usage. But because green roofs can help cool the area, this can cut cooling costs significantly, often up to 25%.

Lower air pollution

Green roofs help cut down on air pollution in three ways. First, because they reduce energy consumption, fewer greenhouse emissions are released into the atmosphere. Secondly, plants naturally remove pollutants from the air by using their leaves and roots to absorb them. Finally, plants put more oxygen out into the air.

Water conservation

Through two processes – evaporation and transpiration – much of the stormwater that falls on a green roof can be captured and sent back into the atmosphere. In the winter, it’s estimated that as much as 40% of precipitation can be retained, and this number goes up to as much as 90% in the summer. And because green roofs absorb so much water, this can prevent excessive runoff and perhaps even flooding during the rainy season.

Points toward LEED certification

For building owners that want to show their commitment to the environment, a green roof is the clear way to do it. But it also can help them achieve Leadership in Energy and Environmental Design (LEED) certification. LEED is a system that rates buildings based on different factors, including energy efficiency, and a green roof can earn a building up to 34 points.

Improved aesthetics

While it’s always good to help Mother Nature, it is even better when you can look good doing it. A green roof is a striking addition to a building. And when it comes to growing things, the sky is the limit. Aside from grass and plants, an assortment of different flowers or shrubbery can be grown. In some locations, green roofs have sprouted urban farms that grow fruits and vegetables. Also, a green roof can offer building employees or residents a beautiful communal spot where they can relax.

Interested in a green roof for your building?

Whether you want to help the environment, save money, create a sky-high oasis, or all of the above, a green roof may be ideal for your commercial building. If you would like to get more information about the installation process, costs, or anything else, get in touch with Peck Brothers. If you’re not ready to completely go green with your roof, we can also discuss other options, including solar panels. Contact us by phone at 201-791-3235 or send an email to

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101 Van Riper Ave. Elmwood Park, NJ, 07407

Phone: 201-791-3235