Jul 09

Can Garden Roofs Combat Global Warming?

Green Roofs Are Winning The Battle Against Climate Change

Find out how garden roofs full of green vegetation help to both insulate and cool our buildings whilst reducing the acidity of rain in our cities.

New research from the Proceedings of the National Academy of Sciences in the US suggests that the answer to combatting climate change might lie at the tops of our houses. Traditional roofs are usually black and made from substances such as tar. These types of roofs absorb heat which make the buildings beneath them even hotter. During the summer months some of these roofs reach temperatures of 70C and an entire city of black roofs can mean that local temperatures are raised by a degree or two.

Yet a solution can be found with the introduction of garden roofs, which are also known as green, cool or living roofs.

What Is A Garden Roof?

A garden roof is one which is covered in vegetation. Typically they consist of a base layer of felt which must be strong enough to retain water and feed the plants and grasses on top of it. The felt is then covered with about an inch of soil which is commonly made up of substrates such as clay and porous shales. The vegetation then completes the top layer of the garden roof.

Heating And Cooling Benefits

By covering your roof in greenery, you will benefit from a cooling effect during the summer months and will need to spend less money on air conditioning systems in order to enjoy a pleasant room temperature in your building. However, during the winter months a green roof adds an extra layer of insulation to a property which means that fuel bills for heating also go down. On a personal level, this means that you will save money on monthly energy bills throughout the year. However, if everyone committed to covering their roofs in vegetation then it would also have an enormous impact on climate change at a global level. This is particularly the case as plants remove large amounts of carbon dioxide from the atmosphere.

A recent study by scientists in the Maryland and Michigan areas of the US, measured carbon levels from 13 rooftops over the space of 2 years. Their findings proved that if an urban area with approximately 1 million inhabitants was covered in green roofs, then an estimated 55,000 tonnes of carbon would be removed from the environment. This is the equivalent to eradicating 10,000 trucks from the road over the same period.

Acid Rain 

Green roofs also absorb more rainwater which reduces the water run-off and wastage that is associated with black roofs. In fact, some people also build blue roofs, which collect water to reduce flooding. However, the greenery also manages to filter the rainwater to make it less acidic. In a densely populated urban area such as New York City, the rain falls with a pH level of approximately 4.2 which is quite acidic. However, precipitation that has been filtered through a green roof comes out as 6.2 which is significantly more alkaline. The cooling effect of the rainwater which has been evaporated from rooftops also reduces the local temperatures by 2C.

It is clear that garden roofs provide benefits to both the homeowner as well as to the environment. If you are considering looking into converting your roof into a garden in order to save money and affect climate change for the better, then always make sure that you get in touch with an experienced roofer who has adequate roofing insurance to complete your job safely.

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Nick Watson is the Chief Operating Officer of BrokerPower.co.uk, which provides pub insurance to UK public houses and bars.