Ethelred Estate - the green roof revolution

A package of regeneration at Ethelred

Ethelred TMO, in Kennington, received a grant from the Government Office for London for the years 2004-2005 and 2005-2006, as well as money from Lambeth Housing for major repairs. Together with contributions from leaseholders, this money is being used to carry out a number of improvements to the estate. These include new sedum roofs for many of the medium rise blocks, which basically involves putting plants on the roof.

What are sedum plants?

The photograph below shows a type of sedum plant known as Spurium Summer Glory. There are many different varieties of sedum, but they are similar in a number of important ways, which makes them suitable for using on the roof:

• They are succulents - which means they store a lot of water in their leaves, making them extremely drought resistant.
• They are small plants, preferring to spread across the ground rather than grow upwards, which makes them excellent for protecting a roofing membrane beneath.

What is a sedum mat?

A sedum mat is a like a carpet of sedum plants, rolled onto the roof after all the waterproofing and drainage layers have been installed. This is what now covers over 4000m² of roofs at Ethelred. This is the biggest area of green roofs on a refurbishment in the UK.

What advantage do sedum mats provide?

Environmental benefits

Residents at Ethelred are excited about the possibility of small garden birds making a come back in the area. Dusty Gedge, of livingroofs.org, even thinks they could see the return of the Black Redstart, which hasn't been recorded nesting in Lambeth for over 20 years.

During storms, the hard surfaces of London's streets and roofs causes water to run off into drains and sewers very quickly. Sometimes these channels become overburdened, and spill out onto streets or into rivers. Marine life in the river Thames suffered from such an event in the summer of 2003, when so much sewage spilled into the river that most of the fish died, starved of oxygen. Green (living) roofs help to slow down the rate at which rainwater finds it way to the drains, and helps to avert such catastrophes.

Social benefits

At home, staying warm in the winter and cool in the summer is very important. The sedum plants provide an effective layer of insulation which helps address both of these things, which also saves energy, which saves money.

Residents at Ethelred are pleased with their green roofs. Many have commented that they are pleased "something green" is happening in their neighbourhood.

Economic benefits

Damage from UV light is often the primary reason a flat roof needs to be replaced. Because the sedum plants help to intercept, absorb and reflect UV light as it meets the roof, the sedum mats are expected to extend the life of the roofs at Ethelred, by as much as twice. The additional up front cost of the roofs is estimated to be around 15% above a traditional flat roof, so they do look like excellent value.

What is the future?

In the future, Lambeth Housing is looking to go one step further for wildlife. Green roofs don't have to be made up of sedum plants, you could also have a wildflower meadow, or even a landscaped park.