When it comes to greening our houses, we all know about insulating our walls and draught-proofing, but the latest big thing in environmentally sound building technology is… plants. Sarah Lewis investigates the eco craze for covering buildings in foliage.

The carbon offsetters may not quite have the bigger picture in focus, but they have one thing absolutely right: planting green stuff is good.

In fact, sticking plants and trees in the ground is so good, a study by the University of Manchester calculated an increase in green cover in our cities of just 10% could lead to a surface temperature decrease of as much as 4C.

Climate change is predicted to lead to hotter summers and colder winters, and those hot summers can kill.

An estimated 35,000 people died in the 2003 heatwave across Europe, the greatest number in cities.

On the whole, urban areas are hotter than their rural counterparts, sometimes by as much as 5C. The change in land use is the main cause, with darker concrete and tarmac absorbing more heat than reflective, shiny greens. The next to blame is waste heat from energy use.

Smothering our streets, roofs and walls in leaves and flowers is one way to help mitigate these temperature rises, but that is not the only advantage to greening our cities.

At Brighton and Hove City Council’s seventh annual sustainability conference, held last week at Bellerbys College in the New England Quarter, the hot topic was the city’s application to be a Unesco Biosphere Reserve.

The title would mean the United Nations Educational, Scientific And Cultural Organisation (Unesco) recognising Brighton and Hove as one of the most biodiverse and green cities in the world. In order to do this, it must “promote and demonstrate a balanced relationship between humans and the biosphere”.

The 12 speakers discussed the advantages of encouraging plant life to thrive in cities at length and, in particular, what it would mean for Brighton and Hove.

Speaking at the conference, Professor Helga Fassbinder, editor of Biotope City Journal, a magazine examining the integration of nature and city, said: “Providing the city with green cover seems obvious.

It addresses both problems of climate change and biodiversity at once and it integrates the red of bricks with the green of nature. It is also something people can see and sustainability must be tangible and visible before people can take it into their hearts.”

Mathew Frith, the landscape regeneration manager for the Peabody Trust housing association, talked about our disconnection from nature and how we have become environmentally illiterate over the past two or three generations.

He suggested this has left our children with “nature deficit disorder” and the knock-on effects of childhood obesity, ADD and general depression.

Indeed, Dr William Bird, the strategic health advisor for Natural England went on to comment that recent studies showed a walk in the park could be as effective as antidepressants in some circumstances.

With one in six UK adults affected by mental illness, Dr Bird says: “something has gone very, very wrong”, yet increasingly evidence suggests both mental and physical health is improved by moving away from our unhealthy, stressed environments and towards more contact with nature.

It seems we have all these problems: climate change, biodiversity loss, mental illness, obesity, and all the pointers are a few more trees and a handful of herbaceous borders are a pretty good fix. Putting them on our streets is a start, but putting plants on our roofs and walls comes with added value.

Not only do they create much-needed and attractive outdoor spaces and enhance biodiversity, but they can provide flood relief, improve insulation of homes and improve the appearance of the city.

James Farrell is the chair of Brighton and Hove Building Green, a voluntary forum set up to “promote the use of plants on roofs and walls as a contribution to a sustainable Brighton and Hove”.

He says: “Green roofs are not the solution to everything. They are not going to solve world hunger. But I think they are a very, very important part of our armoury in the fight for sustainability.”

There are already a handful of green-roofed buildings in the city, such as the Crew Club in Whitehawk, Diggers in Hollingdean, Downs Link College on Surrenden Road and the King Alfred Leisure Centre, but James says: “To make a big contribution it has to be widespread, not just one roof here and there.

It needs to be adopted in planning policy and rolled out everywhere.”

Countries such as Austria, Switzerland and various American states have already implemented incentives for green roofing, with authorities calculating how much they need to reduce mid-summer inner city temperatures and applying incentives in planning policy.

According to James, in Brighton and Hove the benefits we are likely to see include a significant contribution to storm water management by absorbing heavy rainfall and increased habitats for wildlife.

As for planning policy, changes are brewing, as you can see in the New England Quarter, with a handful of green walls growing up the side of Bellerbys College and a scattering of green roofs. James says: “There is certainly not enough. We want those policies to be as strong as possible with green roofs and walls in all new developments.”

A spokesperson from Brighton and Hove City Council said: “Our draft Nature Conservation and Development Supplementary Planning Document (SPD) includes an innovative nature points system, which promotes the use of green roofs and other nature conservation features. It takes the size of the development and the impact on the environment into account to ensure ecological gain is maximised. The SPD is planned for adoption early in 2009.”

  • Find out more about green roofs at Green Up Your Home, an event by the RIBA and the Low Carbon Trust. Guest speakers from BBM Sustainable Design, Climate Outreach Information Network, The Green Roof Consultancy, Low Carbon Trust and RIBA South East. Tuesday, November 11, 6pm-8pm. Free. The Thistle Hotel, Kings Road, Brighton.