Green Roofing: Pros and Cons of Having a Green Roof

Green roofing in Chicago, Illinois
Green roofing in Chicago, Illinois

You might not know this, but green roofs have been around for a long time. In some parts of the world, they are making a comeback.

The Hanging Gardens of Babylon – which was one of the 7 wonders of the ancient world – was a terraced garden structure outside of modern-day Baghdad that used a complicated irrigation system. In Germany, many homes are required to have green roof space.

What is a Green Roof?

You may read this and think it’s about “green” roofing materials or practices: you know that catch-phrase used to describe environmentally friendly things? It actually means having a literal green roof. Like a garden on your roof, complete with soil.

Now, before you get excited and start pitching dirt onto your asphalt roof, there are a few things you need to know. There are two types of green roofs, extensive and intensive.

Extensive green roofing is made up of a thin layer of soil planted with hearty ground-cover plants that require very little maintenance.

Intensive green roofs are basically like parks with a much thicker level of soil, plants – even trees – that require maintenance and even sometimes buildings. Chicago’s City Hall is a famous example of a green roof that has both extensive and intensive elements.

Green roofs can be very heavy. Intensive roofs can create a load of up to 100 lbs per square foot. Extensive roofs can still be very heavy at up to 50 lbs. per square foot. For a building not already structurally ready to support that load, the needed changes can cost a lot up front.

Price of Green Roofs

Green roofs can be quite pricey and hard to maintain. Because they need multiple layers and systems, green roof pricing can start at $8 per square foot, as opposed to the just over $1 per square foot of a regular built up roof (flat roof) price. Plus, you do have to make sure the plants get enough water, which could require some type of irrigation system, depending on where you live.

Advantages of Green Roofing

Green roofs do a lot of great things, which is why the city of Chicago has an incentive program for businesses and homeowners who are willing to incorporate green roofing.

Urban areas, especially, create what’s known as an urban heat island. Asphalt and concrete heat up quickly and hold heat the way vegetation does not. Cities trap heat and drive up the cost and the environmental damage of trying to mitigate all that heat.

Green roofs stay at outside temperature, whereas traditional roofing materials can soar up to 90 degrees above outside temperatures. Obviously, if you can keep your roof cooler, you can minimize the amount of air conditioning you need and do your part to protect the environment from more CO2 emissions.

Green roofs also can provide habitat for animals in the midst of large swaths of land that would otherwise be hardscape. They can protect your roof from UV wear and tear, making it last twice as long.

Green roofs also act like a sponge, soaking up extra stormwater that would otherwise run into the sewers and potentially cause an overflow. The other great natural benefit of a green roof is called evapotranspiration. It’s when, as water evaporates from plant leaves, the air is cooled.

Of course, green roofs are also more attractive than more traditional roofing. Accessible green roofs provide a place for office workers or residents to have a private garden or break spot. Nonaccessible green roofs can still be seen and enjoyed by neighbors.

Take Away

Green roofing is more environmentally sustainable. There’s no doubt about that. It might take some time to catch on because of the expense and the need for retrofitting. However, with government programs designed to promote green roof spaces, it may become the new roofing material of the future.

Over to You

What do you think about green roofs? Do you think they are the roof of the future?

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