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Green roofs

[Sustainable products] Easy to install and delivering real benefits, green roofs are more popular than ever, says Sandy Patience

Cynics point to the proliferation of green roofs and claim that, like strapping wind turbines to a building, they are an easy route to green credibility. However, green roofs can deliver real environmental benefits.

Since entering the mainstream, recognition of the many benefits green roofs can bring has been reflected in the growth of policy, planning support, research and technological development.

London is at the forefront of policy, where green roof installation is encouraged through the London Plan. The Environment Agency also publishes an online toolkit to help developers and designers through the decision-making process.

Because of their low demand on structure, maintenance and budget, ‘extensive’ green roofs continue to be the most specified. More rapid installation with lower risk of failure is enabled through the development of pre-cultivated sedum blankets brought to site and laid upon single integrated filtration, drainage and protection layer systems.

Another development that offers rapid green roof installation is the grid module. Containing the entire planting and substrate within small plastic ‘baskets’ located together over the waterproofing layer, modular systems claim advantages of prefabrication and flexibility.

In recent years, the well-known ‘extensive’ and ‘intensive’ planting systems have been joined by a variation that recognises the importance of local habitats. A ‘biodiverse’ or ‘brown’ roof is a green roof designed specifically to encourage biodiversity through using local soil and spoil. Emphasis is on naturally occurring growth rather than planting imposed by the designer.

Designing a green roof involves the selection of a number of components that will include membrane protection, a drainage system, a growing medium as well as the planting. Products can be combined from a number of sources, but most roof membrane manufacturers offer, themselves or with horticultural suppliers, complete systems.

ALUMASC

Alumasc

Alumasc

Combines hard and soft landscaping to offer benefits associated with small urban parks or roof gardens, providing habitat for wildlife and recreational space for people. The greater substrate depth facilitates improved plant species diversity, stormwater attenuation and insulation.

Manufacturer Alumasc
Product ZinCo intensive system
Growing medium 150-1500mm
Drainage layer Recycled, hardened polyethylene with storage and irrigation reservoir properties
Build-up height (lawn approx) 270mm + turf
Other systems Extensive, semi-intensive, bio-diverse/brown roof
www.alumascwaterproofing.co.uk

TRELLEBORG

Trelleborg

Trelleborg

GreenGrid offers a modular design that contains all the separate layers that make up a traditional green roof in one unit. The modules arrive on site preplanted and ready for installation, lessening the risk of plant failure.

Manufacturer Trelleborg
Product GreenGrid modular system
Growing medium 100mm of lightweight material
Drainage layer Incorporated within the module
Build-up height (approx) 100mm
Other systems Semi-extensive, intensive, bio-diverse/brown roof
www.trelleborg.com/waterproofing/uk

IKO

IKO

IKO

A form of extensive roof that makes use of recycled materials in the growing medium. This type of green roof is intended to create a natural wasteland and can be seeded initially with selected species to create some growth.

Manufacturer IKO
Product Biodiverse (brown) roof
Growing medium Specially formulated mixtures
Drainage layer An integrated polystyrene sheet with a non-woven filter fabric
Build-up height (approx) 175-275mm
Other systems Extensive, intensive
www.ikoroofing.co.uk

BAUDER

Bauder

Bauder

A biodiversity roof that provides a natural living habitat to encourage a wider spread of birds, insects and plant species in the area. It generally seeks to replicate the ecological environment of the site upon which construction development is taking place.

Manufacturer Bauder
Product Biodiverse green roof
Growing medium Lightweight growing substrate, depth dependent on the selected planting scheme
Drainage layer Polyethylene reservoir/drainage board
Build-up height (approx) 100-400mm
Other systems Extensive, intensive
www.bauder.co.uk

SIKA SARNAFIL

Sika Sarnafil

Sika Sarnafil

Extensive systems are selfsustaining, naturalistic and low maintenance. Suitable for both flat and pitched-roof applications, they provide a raft of building performance benefits, reduce building impact and over time create a general habitat for a variety of flora and fauna.

Manufacturer Sika Sarnafil in conjunction with horticultural partner
Product SarnaVert extensive green roof
Growing medium 65-150mm of lightweight growing material
Drainage layer Recycled polypropylene drainage and protection layer
Build-up height (approx) 100mm
Other systems Intensive, brown/bio-diverse
www.sarnafil.co.uk

LANGLEY

Langley

Langley

The low growth characteristics of sedums makes them particularly suitable for growing in the inhospitable conditions found on roofs. It is the very nature of the sedum plant that makes it perfect for survival in drought conditions.

Manufacturer Langley Waterproofing Systems
Product Extensive green roof system
Growing medium HDPE drainage layer incorporating filter fleece and 40mm extensive substrate mix containing clay minerals and plant nourishment
Build-up height (approx) 70mm
Other systems Intensive
www.langley.co.uk

 

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