Zoontjens on bringing nature to roofing

Green roofs are well known for their contribution to reducing the carbon footprint and improving EPC performance, but the green building principle does not stop there.

As part of the Energy Performance of Buildings Directive, public buildings in England and Wales will have to display an Energy Certificate.

This requirement came into effect on 6th April for large commercial buildings with a total floor area greater than 10,000m2.

As energy prices increase, the cost of cooling air conditioned buildings in summer now routinely exceeds the costs associated of heating them in winter.

The opportunities to improve energy efficiency can only be welcomed.

Green roofs are well known for their contribution to reducing the carbon footprint and improving EPC performance, but the green building principle does not stop there.

Lightweight green roofs and facades are now available to create living environments where previously they would have been impractical.

Academic research at Universities such as Cardiff and Sheffield has shown they can make a tangible contribution to maintaining a regular temperature in buildings.

Some lightweight systems use panels fabricated entirely from post-use recycled plastic which would otherwise be sent to landfill.

Providing significant water retention characteristics, a product such as Aquadyne has been shown to be capable of retaining 22 litres of water per square metre, weighing only 35kg/m2 when saturated.

The equivalent storage capacity using stone (pea shingle drains for example) would weigh in the region of 130kg.

In addition to its significant attenuation and drainage properties, in tests verified by the University of Newcastle, a tangible saving of 1 tonne of CO2 / 22m2 has been proven.

The base sheet acts as wick, water store and diffuser, and assists with storm water attenuation.

It enables plants to be grown, fed and irrigated, the soil-less structure avoiding risk of soil slippage.

Used in conjunction with rainwater harvesting systems, such soil-less technology must meet the standards of BS EN 6920 - non-metallic products for use in contact with drinking water and the needs of SUDS.

In addition, they have to be suitable for vertical, pitched and horizontal surfaces and enable retro-fitting to existing buildings.

Depending upon the chosen system, lightweight options can reduce the substrate weight by more than 50%.

A variety of planting options is available, dense evergreen, self-seeding and non-invasive varieties with creeping root structures (such as birds' foot trefoil and rupturewort) requiring little more than annual inspection.

In the case of some Aquadyne applications, the panel's inherent properties enable such species to be used without irrigation for in excess of 3 weeks.

In addition, it prevents long-term problems traditionally associated with clogging, soil settlement and filtration failure.

Whilst the boundaries between sustainability and environmental credentials are often confused, green roofs contribute to overall sustainability by, for example, protecting the membrane and roof construction from the effects of UV light.

The protection also enhances whole life cost performance of the roof.

In addition, combining specialist roof paving with attenuation systems and green roofs will also significantly improve the EPC performance.

Suitable for cold, warm or inverted decks, roof decks at various levels can be linked to create a fully co-ordinated roof environment.

For pedestrian areas smaller slab profiles can even be produced to bespoke design.

The green roof concept is clearly no longer a purely urban design luxury.

As the demands for sustainable development have increased, many consider that the improved thermal efficiency of green roof and facade systems has been instrumental in their long overdue success.

Reduction in rainwater run-off of 60-70% has also become increasingly significant as building densities and flood problems in urban environments have increased.

Retro-fitting has become a more practical proposition as the structural considerations which would once have ruled out a green roof need no longer apply.

Increasing product sophistication involving intensive planting has increased scope for designers and successful green roof schemes have attracted a wider audience for urban regeneration designs.

It has also prompted use of the principle for ground level landscaping.

Even without any national strategy, the momentum for green roofs is growing and legislation to mitigate loss of open space can only be a matter of time.

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