This article investigates the sustainability benefits of green roofs. It was inspired by reading Green Roofs: Ecological Design and Construction. I thought this was an impressive book, and I learned a lot by reading it. It comes highly recommended from me.

In the preface by Earth Pledge Executive Director Leslie Hoffman, she shares an excellent quotation which I will post below:

“Green Roofs represent an elegant opportunity to simultaneously mitigate environmental problems and create immediate life-enhancing value. They individually offer building owners savings on energy and roof membrane replacement costs, while also greening the cityscape for owners and residents of neighbouring buildings. Flowering and native plants help cool the urban landscape and combat the pollinator crises in our region, and one doesn’t need to hear much about combined sewage overflow and the erosion and runoff issues in coastal zones to understand why pervious surface is desirable.”

In terms of the environmental benefits of green roofs, these can be broken down into a few categories.

Climate change

Green roofs help to address climate change by reducing the urban heat island effect. This is a phenomena where urban areas warm to a greater extent than rural areas.

Green roofs accomplish this by warming less in summer. Where an asphalt roof could reach 160^oF, a green roof would rarely exceed 80 ^oF.

There is also another green roof phenomena called evaporative cooling, which reduces heat transfer through the roof into the building, making the inside cooler and reducing the air conditioning load.

Hydrology

Urban infrastructure disrupts the natural movement of water, known as the hydrologic cycle.

Green roofs can help to solve this problem. They retain and detain stormwater, reducing runoff volume and slowing the rate at which it enters the sewage system.

Delaying the runoff is as important as reducing its volume, as this helps to prevent waste water systems from becoming overloaded.

Urban ecology

Green roofs can act as an ecological beacon in urban areas and support biodiversity.

Green roofs can be designed to protect endangered plant species, or to blend in with the local habitat.

Other roofs, so called brown or rubble roofs take material that is excavated during the build and use that soil to create a green roof on the finished build. The hope is that this is naturally colonised by indigenous plants and supports local ecology.

Green roofs can also support many varieties of bird and insect that would not survive without the habitat that they provide.

What you need to know

This article investigated the sustainability benefits of green roofs.

It was based on the book Green Roofs, by Earth Pledge, it comes highly recommended from me.

Green roofs provide many benefits, but particularly in terms of climate change, hydrology and ecology.

People are always looking for breakthrough technologies that will make the built envelopment more sustainable. Green roofs could be one of those solutions.

Thank you for reading,

By Barnaby Nash

Please share your thoughts in the comments section below or reach out to me on social media. What do you think needs to be done to promote the benefits of green roofs?

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