Raising the green roof

Green roofs boast many benefits from providing insulation and absorbing rainwater to helping to lower urban air temperatures but are they suitable for mass installation?

A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems.

There are two types of green roofs: intensive roofs, which are thicker and can support a wider variety of plants but are heavier and require more maintenance, and extensive roofs, which are covered in a light layer of vegetation and are lighter than an intensive green roof.

At the recent New Designers Exhibition – showcase for the UK’s best graduate design student work – Brunel University student, James Ward, Industrial Design and Technology BA, unveiled his plans to bring Green Roofs to the mass market.

His design uses carpet fibre as an alternative to soil – helping to solve the problem of old carpet materials ending up in landfill. Plastic tiles replace slate – and these can be produced out of recycled products.

Secondly the tiles are specifically designed for pitched roofs. Currently ‘Green Roofing’ is only available for flat roofing, but Ward felt this was missing a trick, as the majority of buildings outside of high-rise office buildings have sloping roofs.

The tiles are designed to slot together in a similar way to traditional roofing tiles, making it easy for people to install the roofing themselves, and the grips built into the tile holds the carpet fibres in place.

James says: “Green roofing and turning eco is the way forward. We have got to change our ways; all this gas guzzling is killing the environment. You look at cities and you look at reports and it is full of issues like the Urban Heat Island and water absorption issues.

“Green roofing helps to tackle all of these and it brings wildlife to the environment. It brings benefits to the environment but also people who live in these green roofed houses. It increases their insulation and brings down energy costs.”

One of the perceived barriers against green roofs is the structural implication to the building. Green roofs promoter livingroofs.org says: “Any landscape feature on a roof will have loading implications and the saturated weight of any such features must be used to calculate the structural load. It is interesting to note that many inverted roofs are covered in paving slabs in order to ballast out the insulation. The use of an extensive green roof system would have a negligible effect on the structural load in this instance.”

Recently a structural report for a current commercial building in London allowed for an extensive green roof to be applied on top of the paving slabs of an inverted roof without any negative structural implications.

As design applications and experimentation in lighter materials progresses, then the potential for seeing our town and city roofscapes turning an eco shade of green looks a lot more promising.

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