Green roofs and why the UK needs to get up to speed
With space at a premium in the UK, it’s time to look up and rethink how we design our roof tops.
There are some incredible examples around the world of buildings already doing this well, from eight level rooftop gardens in Japan to a 2.5 acre living roof on the top of the California Academy of Sciences in America.
The Vancouver Convention Centre in British Columbia has a six-acre roof and is one of the ten largest green roofs in the world. Even the roof of Gap’s headquarters in California is covered in native indigenous grasses and wildflowers cultivated from native grasslands.
Here in the UK you can spot an intensive green roof on some large commercial buildings such as New Providence Wharf in Docklands, which covers an area of 8.3 hectares. It’s one of around 700 green roofs in central London.
Closer to our studio in Cheshire, Chester Bus Interchange was designed with a green roof to help to improve air quality, biodiversity and wildlife in the city centre as well as reducing the effect of the drainage run off on the sewer network.
Green roofs are starting to gain popularity in the UK but we need to speed up and catch up with other European cities who have been making them part of the urban landscape for decades.
We could learn a lot from Stuttgart in Germany which is considered to be the ‘green roof capital of Europe’. This is mainly down to a forward-thinking government and their enhanced environmental policies. Many of its municipalities are using regulations to make green roofs mandatory, so it’s little wonder that they have become an accepted standard in the building industry.
In the UK, the environmental regulations in the building sector aren’t well accepted and it’s why cities have been left to develop individual policies. One of the reasons why London is home to much of the UK’s green roof market is because the London Plan has doubled the use of green roofs since 2008. Cities outside of the capital should take note.
There are “living labs” at both the University of Sheffield and Salford which are helping to establish precedent to convince developers and investors to adopt green roofs and show the benefits these can bring but government environmental policies are required to drive this. Perhaps the new Biodiversity Net Gain regulations coming in from this month could help with the push for the green roof on inner city developments.
We certainly need more green roofs. Urban densification is rapidly eroding our green spaces and in order to have sustainable and resilient cities in the future, nature reintegration is essential.
How do we do it? Unused roof spaces could contribute to the solution but only if projects include green/blue roofs in their specification right from the start. Too often, photovoltaic panels or other renewable energy technologies take favour, but why can’t we have both?
Integrating renewable technology and rooftop vegetation innovatively can optimize roof spaces, offering climate-smart energy while enhancing biodiversity, stormwater retention, and temperature regulation.
Green roofs could also be combined with a blue element which by managing water at its source to replicate natural processes either through irrigation of the green roof, reuse within the building, or storage to slow water down, can help towards reducing flooding to our downstream receptors.
The photovoltaic panels on our roofs when combined with vegetation could help to cool down the environment and therefore increase energy efficiency. Using the PVs to shade vegetation in the summer also helps provide better drought resistance during dry periods.
We need better investment too. Cost is a common initial obstacle due to the additional structural support required to handle any increased loading. However, over time the green blue roof can more than make up for the outlay when you consider the additional benefits.
Conducting a comprehensive cost analysis is essential, examining not only the savings in construction expenses associated with excavating large holes for subsurface water attenuation but also considering the overall life costs associated with improved energy efficiency through water reuse and mitigating the heat island effect.
Maintenance of plantings is a debated concern but if designed early within the process, with the correct planting specification, the maintenance may actually not be as onerous as believed. After all, photovoltaics need ongoing maintenance.
A comprehensive design should cover waterproofing, water storage, penetrations, soil specification, and vegetation selection.
If this design approach doesn’t currently fit with how consultants are appointed on projects, something needs to change. After all, if we want to use roof spaces more efficiently, and catch up with Europe, we need to crack on and build more green roofs.
Our green roofs in Gibraltar
One of our green roof projects was in Gibraltar on a luxury apartment development. We took inspiration for the rooftop gardens from the dramatic landscape of the nearby Rock and specified drifts of flowers and grasses, statement planting pots and trees to bring the landscape into the site and also to frame the views. Find out more here.