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Design For Living

August 1, 2006 6:00 PM
By Carolyn Fry in IEE Review
Apartment Block

BedZED Apartment Block

The BedZED architectural project in South London aims to deliver high living standards with low environmental impact.

A report published this year by conservation organisation the WWF estimated that the average person in the UK has an 'ecological footprint' of 5.4 global hectares. A global hectare is a hectare of globally productive space with an output capacity equal to the average capacity of the 11.4 billion productive hectares on the planet. The figure means we each need that amount of land to produce the food, clothing, energy, water and other materials we consume throughout our lives. The imbalance that has long existed between rich and poor countries has enabled us to get away with far more than our fair share for a long time. But populous developing nations such as China and India are understandably now keen to take up their place in consumer society, putting an additional strain on the world's resources. The report concluded that if the world's six and a half billion inhabitants all began consuming at the same level as the UK, we would need three planets to support us. Clearly, we don't have three planets, so our only option is to reduce our ecological footprint. But is it possible to live in a more sustainable manner, without making huge compromises to our standards of living?

Origins

Roof garden

Roof garden

An architectural project in south London, the Beddington Zero-Energy Development (BedZED), is living proof that we can. The UK's biggest eco-village, BedZED is a high-density development of 99 residential properties ranging from one-bed flats to four-bed houses, plus 1450m2 of office space - all designed to be powered by non-fossil fuels. The development integrates privately owned flats and houses with social and key-worker housing. It came about through a co-development between the Peabody Trust, the charity BioRegional Development Group and Bill Dunster Architects (BDA).

"Bill Dunster had finished building Hope House in Thames Ditton, a prototype ZED design," explains Kate Millbank, communications officer for BioRegional Development Group. "He was then looking to design and build a ZED on a much larger scale that incorporated residential and office space as a live-work community. At the time, Bioregional was looking for environmental office space so Bill and Bioregional's co-founder Pooran Desai got together and began moving the idea forward. Peabody Housing Association came on board as the developer, because its social agenda to reduce fuel and car poverty among residents very much matched Bioregional's and BDA's environmental agendas."

Low Energy

PV cells

PV cells

The prime aims of the development were to reduce the amount of energy required by the housing and office units, and then to supply the power that was needed through on-site renewables. The building's design has been fundamental to lowering energy needs. For a start, the office space is located on the north side of the blocks and the residential units on the south side. This is because you generally need to heat houses more than you need to cool them, and cool offices more than you need to heat them. Each terraced block is built with a south-facing triple-storey glass 'sun-space'.

On the ground floor, this tiled conservatory-cum-entrance hall overlooks a small garden. On the second floor, it provides access to a bridge leading to a roof garden on the north-facing side of the next block. The idea is that the sunlight enters these spaces throughout the year, even at winter solstice when the sun is at its lowest point in the sky. Because the internal concrete walls have a high thermal mass, heat coming in from the sun is stored in the building fabric and re-released throughout the day. Each block is also wrapped in a thermal jacket of 300mm-thick rockwool insulation. The outcome is that the internal temperature stays at around 18-21°C throughout the year. "We don't need any heating at all in the residential units so there are no central heating units installed," says Millbank. "There is one radiator in the bathroom, and every unit has an oversized hot-water tank. If the temperature drops a little, all the residents have to do is open the doors of the airing cupboard and let the excess heat from the tank warm the air. There is heating in the office spaces, but there's no air-conditioning at all."

So far, the only real problem with this simple method of heating has been one of too much, rather than too little, heat. Some of the top-floor flats have glazed roofs on their sun spaces, which has sometimes pushed up the temperature too much on the upper levels. This is now designed as a solid roof in similar ZED ventures. For cooling, residents simply open and close windows. Because of the high mass of the building, the internal temperature does not fluctuate quickly, even if the external temperature changes. This is similar to how a church can stay cool on the inside, even if it is hot outside. There is also a ventilation system to keep fresh air circulating through the houses.

Air Flow

Wind Cowling

Wind Cowling

As you approach BedZED from its nearest station, Hackbridge, you get glimpses of the roofs of the terraces behind other mainstream houses. It's an unusual sight, because the roofs are topped by a series of multicoloured wind cowls, which look a little like the combs of giant metallic cockerels. As the wind blows, fins catch the oncoming wind and swing round, drawing cool, fresh air into the houses through air vents positioned low-down on room walls. At the same time, warm, stale air rises and is expelled through ducts positioned higher up on the internal walls. When it's not windy the ventilation works on a 'passive stack' system, with the rising warm air naturally drawing in cooler air. There's a heat exchanger within the cowls, so as the cool air comes in it passes over the outgoing warmer air and is slightly pre-heated. The cowls are an important part of the design because the units are so airtight. "The buildings have a very low U-value - that's the rate at which the heat is lost through a surface, in this case the walls," says Millbank. "It's around 0.1W per metre-square Kelvin 0.1W/m-2K-1 which is about two-and-a-half times better than the 2002 building regulations."

Electricity Supplies

Sun-space

Sun-space

All units have light fittings that can only be used with low-energy CFL (compact florescent) light-bulbs, and all the appliances are A-rated for energy efficiency. This has reduced the electricity needs of BedZED inhabitants by 25%. "The UK average is 4kWh hours a day and at BedZED its about 3kWh hours a day but it does vary enormously," says BioRegional's Jess Hodge. "Some people are very careful but some use much more than the UK average. Not everyone who lives here is an eco-angel. Some people just moved here because it happened to be at the right price and area for them, and electricity use is very much related to lifestyle."

Electricity is usually provided by an on-site combined heat and power (CHP) unit located in a separate building plus 777m2 of photo-voltaic cells positioned on the terraces' roofs and windows. Initially, the CHP plant was designed to provide all the electrical and water heating needs of the site, while the PV cells powered a fleet of electric cars.

Running On Wood

The CHP plant is powered using woodchip biomass from Croydon's TreeStation, three miles away. The TreeStation receives waste wood from many sources, turning it into woodchips to provide fuel for heating and CHP units. Bioregional set up the supply chain to ensure there would be enough woodchip to meet its needs by charging London's tree surgeon's less than they would usually have to pay to dispose of the wood in landfill. The Tree Station delivers around 20 tonnes of wood per week through the large double doors of the CHP building. Inside, an automated grabber loads the woodchip onto a conveyor belt and spare heat from the CHP is used to dry the biomass to 45% moisture. "We half-burn the woodchip and capture the methane, carbon dioxide and nitrogen that is given off," explains Hodge. "We convert these to electricity by feeding them through a combustion engine like you'd find in a lorry. Ideally you would run it continuously but we were only given planning permission to run it for 18 hours a day."

"Typically, when you generate electricity, you get twice as much heat as you do power, and, as well as drying the woodchip, we use that to heat the hot water and distribute it through a district heating network to the tanks in each residential unit," adds Millbank.

Boiler Problems

Utility Meters

Utility Meters

Although the CHP initially worked to plan, supplying all the hot water and electricity needs of the development, it was not working when I visited. Because the plant constantly had to be switched on and off, condensation built up inside it as it cooled each day, and its built-in self-cleaning device didn't perform its job as well as intended. Hodge explains that these two factors contributed to its failure. For the time being, BedZED is drawing 11% of its electricity needs from its PV cells, as the development has only one electric car, and the water is heated using two back-up gas condensing boilers drawing gas from the national grid. The plan is to install a new CHP unit.

"We have had some problems," admits Millbank. "It was running periodically for a few years when BedZED first started but it never ran to full efficiency. We think the problem has been the type of biomass boiler; it was the first type of its size for this kind of development so it was a bit of a prototype. With CHP you can turn it on and off, but not so regularly, so we think the gas was condensing in the boilers and blocking the filters. This prevented the plant from running at its full efficiency and then slowly clogged it up completely. With all new projects there are hiccups and we are looking at installing a new CHP plant. I think it will be a different model, but we'll still use woodchip."

Although there have been problems, the BedZED has shown that it is possible for high-density housing developments to function without using up vast quantities of fossil fuels. Other features aimed at reducing environmental impacts include using aerated water in taps and low-flow shower heads to reduce water use; planting sedum on roofs to reduce run-off and increase biodiversity; and gathering rainwater in tanks for use in the low-flush toilets. Kitchen units are made from beech wood so contain no formaldehyde and all the paints used in the initial decoration of BedZED were eco-friendly. Split recycling bins in the kitchens make recycling easy; BedZED aimed to cut waste by 60%. Other materials come from recycled sources; for example, the floorboards in the show flat came from the Abbott Public House in Redhill, Surrey.

One Planet

BedZED has inspired the ideology of 'one planet living', a 10-point formula that will inform future eco-developments in Australia, China, North America and South Africa. The points are listed in the box 'Ten Points to achieve One Planet Living'.

"There are changes that we have tried to bring into people's lifestyles but they are all so inherently designed into the architecture that people don't notice that much," explains Millbank. "If you want to buy local food from farmers' markets and use our car club instead of owning a car then that can reduce your impact further, and we encourage residents to do that. So I would say that it is very possible to lead the same if not a better quality of life and reduce a large percentage of your environmental impact living in an eco-house."

Ten Points to achieve 'One Planet Living'

A report published by the WWF estimated that the average person in the UK has an 'ecological footprint' of 5.4 global hectares. This means that, if everybody on the planet laid claim to the same ecological footprint at the average UK resident, we would need three planets to sustain us. BedZED has inspired the ideology of 'one planet living', a 10-point formula that will inform future eco-developments in Australia, China, North America and South Africa.

The 10 points are:

1. Zero carbon

2. Zero waste

3. Sustainable transport

4. Use of local and sustainable materials

5. Use of local and sustainable foods

6. Sustainable water supplies

7. Natural habitats and wildlife

8. Culture and heritage

9. Equality and fair trade

10. Health and happiness.

  • David Goodall's note to reader - this article demonstrates that it is possible to build low carbon housing now, whereas Labour planning regulations plan to achieve this by 2016. Liberal Democrat run London Borough of Sutton have achieved this development today.