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Myth: ‘off the peg’ green roof systems offer best value for money…

by Matt Downs

Fact: As the team at GRO explain, in truth there is no one-size- fits-all solution for green roofs, the best ones are tailored to the needs of the building, its environment and its occupants. 

Have you ever eaten a ready meal from the supermarket? They claim to be delicious, nutritious and satisfying. But in truth they’re not a patch on a custom-cooked meal tailored to your own taste and designed to nourish your body and soul. There’s usually a noticeable price difference between the two ways of eating, but in terms of the overall benefits, it’s the carefully made meal that offers best value.

When biodiversity net gain and carbon plans are viewed as a “box ticking” exercise, it’s tempting for architects and planners to take the route of least resistance when designing and specifying green roofs. There are plenty of systems out there that can be “copied and pasted” onto a plan with very little time spent on research or consideration. However, carefully designed and well executed, green roofs offer so many potential benefits that by employing in-depth knowledge of the principals of green roofing, rather than finding a one-size-fits-all solution, these popular architectural features can become a true asset to an area.

Let’s look at a prime example.

Case study: The Forge, Redclyffe Road, East London
The Forge is a residential development in the London Borough of Newham 

which was built on the site of a former bus depot. The complex of 192 homes is comprised of a mix of one, two, three and four bedroom apartments and town-houses.

The site posed a number of challenges including limited green space at ground level, close proximity to existing properties and strict rainwater management requirements with minimal opportunity for below ground attenuation.

Instead of creating ground level SuDS, water management systems were incorporated into a blue-green roof designed and supplied by Radmat in conjunction with RM_A Architects and Telford Homes.

Because the development needed to meet high thermal standards and provide as much amenity space as possible, as well as managing water, Radmat’s Blue Roof System had to be redesigned several times. In various sections of the roof span there are PV panels, habitat roofs and amenity areas. Each section uses different substrates and plant species in order to maximise the benefits generated by the roof.

Would an ‘off the peg’ green roof system have benefited this development? Absolutely not!

Best practice for bespoke green roof design

For a new building, designing from the top down is one way to ensure that the roof offers maximum benefits. Consider, as the architects mentioned in our case study above did, every possible function of your living roof. Which of those functions should take priority? And how will the roof need to be constructed in order to fulfil that function?

For an existing structure, you may need to consider possible changes to the roof deck and supporting framework in order to accommodate a green roof build-up. Alternatively, it may well be possible to design a green roof that works well within the parameters of the building. 

The GRO Code Of Best Practice provides a wealth of information on how to design a living roof that offers maximum benefits to a building, its occupiers, its neighbours, local wildlife and the wider environment. Download a your copy from www.greenrooforganisation.org/downloads/ or visit the GRO Pavillion at Futurebuild 2023 to collect a printed version.

Green roof training for designers and specifiers

Anyone involved with the design and specification of living roofs will find the Lantra Introduction to Green Roofs course invaluable. The course explores the principals and practicalities of green roof design and construction and will unravel some of the perceived mysteries about this amazing technology. (Visit https://www.lantra.co.uk/product/35103 for more information)

In summary

To create a living roof that will provide best value for money for your building or development, you need to be armed with enough knowledge to assess whether or not a system will fulfil the brief. Price is not an indication of value. 

In some cases an ‘off the peg’ solution, perhaps with a few modifications, will be ideal. However, please don’t be persuaded by the marketing blurb. The team at GRO recommend consulting with an experienced green roof designer before committing to any specific green roof system.

www.greenrooforganisation.org

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