Earthy Thursdays

The Living Roof

This week I want to share something Dana and I have been looking into called the 'Living Roof'. It's a new eco-friendly way to build that has many cost and environmental benefits. Many city buildings are already using these methods and is very popular in the UK.

What is a living roof anyway? A living roof is basically a roof with vegetation or part vegetation, also called eco-roofs or roof gardens. There are three types of living roofs. Intensive, extensive and domestic, which basically range in the height, depth and maintenence of the plants on the roof. So now you know what it is, let's talk benefits.

While 'living roofs' are not that popular yet in rural and suburban Canada, cities like Toronto are already reaping the benefits of these eco-friendly treasures. In a concrete jungle, the obvious benefit is the increase of green space which has been linked to reducing stress and improving health through air quality. But what is the benefit to an average builder?

Let's talk money, because that seems to a driving force in our decision making process.
EXTENDED ROOF LIFE- While most roofs last an average of 25 years, living roofs can sustain for upwards to 60 years so you will replacing your roof basically once in your life if you buy you do the living roof in your early twenties.
ENERGY CONSERVATION- The living roof acts as a natural cooling and heating insulation. A green roof not only acts as an insulation barrier, but the combination of plant processes [photosynthesis and evapotranspiration] and soil processes [evapo-transmission] reduces the amount of solar energy absorbed by the roof membrane, thus leading to cooler temperatures beneath the surface. Green roofs can help to reduce heat loss from buildings during the winter when root activity of plants, air layers and the totality of the specific system create heat and thereby provide an insulation membrane.

The major benefits are for the environment and us sustaining our planet. Did you know that 1.25 million tonnes of asphalt-based roofing materials are discarded annually in Canada. In the United States, the number is between six and nine million tonnes. That's alot of waste in our landfills not to mention the affect that asphalt has to the Green Island Effect.

REDUCTION IN SURROUNDING HEAT-Roof areas are a significant part of urban hard surfaces. Plants on green surfaces absorb heat and then use it through evapotranspiration. Green roofs therefore would play an important role in reducing urban temperatures, and subsequent improvements in air pollution/smog, as associated with the albedo effect.
NOISE AND SOUND INSULATION-The combination of soil, plants and trapped layers of air within green roof systems can act as a sound insulation barrier. Sound waves are absorbed, reflected or deflected. The growing medium tends to block lower sound frequencies whilst the plants block higher frequencies.The amount of sound insulation is dependent on the system used and the substrate depth.
RECYCLED MATERIALS-A number of materials used in green roofs are from recycled sources, such as the membranes and growing mediums, such as crushed porous brick, which is used by some suppliers. In London, uniquely, there has been a move to use recycled secondary aggregate as the growing medium, preferably from the original site.
STORM WATER AMELIORATION-Green roofs store rainwater in the plants and growing mediums and evaporate water into the atmosphere. The amount of water that is stored on a green roof and evaporated back is dependent on the growing medium, its depth and the type of plants used. In summer green roofs can retain 70-80% of rainfall and in winter they retain between 25-40%.

For more information on this great eco-friendly method, check out Living Roofs!