Closing the performance gap

16th January 2015


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Author

Najib Hakim

A new development in Brighton has shown that sustainable buildings can work. Ben Gill reports

The gap between what is promised on paper at design stage and what a new structure actually achieves once it is built and its occupants have moved in is an issue that poses difficulties for those promoting low-carbon buildings. One Brighton, a 172-apartment complex in the seaside city, aimed to set a new standard in sustainability. Has it achieved that objective?

In the four years since the first residents moved in, the complex’s performance has been subjected to intense scrutiny, including an in-depth analysis of its lifecycle carbon emissions. The examination has revealed a mixed but broadly positive picture, with plenty of lessons to apply to other building projects and to the future management of One Brighton itself.

Building on BedZed

The complex comprises two blocks – one 12-storey and the other eight-storey. It was developed by Crest Nicholson and BioRegional Quintain, and was the follow-up to the sustainability charity’s world-renowned 100-home Beddington Zero Energy Development (BedZED) in Sutton, south London. The “eco-village”, which was finished in 2002, remains BioRegional’s head office.

The charity wanted to use the lessons learned from BedZED to work with leading commercial developers and build large-scale sustainable housing projects. Its aim is to bring “one planet” lifestyles into the mainstream. One Brighton returned a profit despite going on sale during the depths of the recession and provides dozens of affordable new homes in one of the most expensive UK housing markets outside London. Just under one-third of its apartments were allocated for shared equity or social housing. A further 11% were built as low-cost “eco-studios” offering people a first rung on the housing ladder.

Among One Brighton’s sustainability features are roof terrace allotments; a living roof planted with cliff-top vegetation; a community composter; a 9.6kW peak output array of photovoltaic (PV) panels; a community centre; and a sustainable food café, which began life as the construction site canteen. A communal biomass boiler provides heating and hot water. Non-PV electricity is purchased through a green tariff backed by Ofgem’s certificate of renewable energy guarantee of origin. One Brighton, which is next to the main railway station and many bus routes, is virtually car free; its few parking spaces are available for disabled users and car club vehicles only.

The building, designed by architects Feilden Clegg Bradley Studios and built by Denne under a design-and-build contract, was engineered to have low embodied carbon with a “green concrete” frame. The cement comprised 50% ground granulated blast furnace slag and all of the aggregates used were from demolition waste. The exterior walls were built of clay blocks fired at low temperatures, which further reduced embodied carbon.

These blocks had a honeycomb internal structure, providing a high standard of insulation. They were covered by a thick layer of wood fibre and finished with a layer of weatherproof mineral render and softwood cladding from an FSC-certified source. Triple-glazed windows throughout maintain the high levels of insulation.

Lifecycle analysis

The lifecycle analysis (LCA) carried out by eTool, an Australia-based software house, estimated greenhouse-gas (GHG) emissions for the entire operational life of the materials used in One Brighton plus those from the construction work and from
final demolition a century from now. For purposes
of comparison, eTool also modelled the GHG emissions embodied within the average new-build UK home. The estimate of the operational emissions from One Brighton was based on the development’s measured energy consumption.

The LCA was an ambitious undertaking, incorporating GHG emission estimates for more than 600 building components, from a variety of raw materials. Key finding are:

  • One Brighton’s lifetime GHG emissions are 60% lower than those of the average UK home. In other homes, the total lifecycle emissions are dominated by operational emissions, which occur while the house is occupied. In One Brighton, the embodied carbon emitted in constructing the building and making all the materials that go into it comprises a much larger part of the total lifecycle emissions – even though these embodied emissions are lower than in conventional housing.
  • The complex’s current emissions performance is not yet achieving design targets. The gap is mainly due to the intermittent availability of the biomass boiler. However, the boiler is not running as much as planned because the engineers oversized the spec and the water demand is lower than was forecast. So far, the boiler is meeting abouty 30% of the building’s heat and hot water demand, with the remainder supplied by natural gas. If BioRegional achieves its target of meeting 90% of the building’s heat demand from biomass, One Brighton’s overall lifecycle carbon emissions would be 78% lower than that of the average UK home. This would be in line with achieving the (near) zero carbon target for operational emissions by 2020.
  • The building’s annual operational carbon emissions were found to be 67% below the UK housing stock average. But they would be 89% below if BioRegional can hit its 90% heating and hot water target from the biomass boiler.

“The LCA shows the very low-carbon fundamentals of the building are sound,” says Pooran Desai, BioRegional’s co-founder, who led the organisation’s involvement in One Brighton. “But we are working to greatly improve performance from the biomass boiler, to reduce operational emissions significantly and take us to our 2020 target.”

Community action

The LCA was part of a wider review of One Brighton’s sustainability performance. The building is one of a growing international family of “one planet” communities, including the Sonoma Mountain village, near San Francisco, and the Grow community in Bainbridge Island, near Seattle. One planet communities aim to adhere to an action plan based on 10 sustainability principles (see panel, p.28).

The most evident benefit for One Brighton residents is that their heating bills are much lower than average. The building’s water-saving features appear to work too, as water consumption is considerably lower than the UK mean. A strong sustainability-minded community with close links between residents has yet to emerge. Many of the units that were sold were bought to let, and are being rented by students, who tend to be fairly transient.

But the positives strongly outweigh this negative. One Brighton has shown that a smart, modern and mainstream housing development can be far more sustainable than the norm, and profitable too. The few apartments that have been sold on since it was completed have attracted relatively high prices.

One planet communities

Health and happiness

Encouraging active, sociable, meaningful lives to promote good health and wellbeing

Equity and local economy

Creating bioregional economies that support equity and diverse local employment and international fair trade

Culture and community

Respecting and reviving local identity, wisdom and culture; encouraging the involvement of people in shaping their community and creating a new culture of sustainability

Land use and wildlife

Protecting and restoring biodiversity, and creating new natural habitats through good land use and integration into the built environment

Sustainable water

Using water efficiently in buildings, farming and manufacturing. Designing to avoid local issues, such as flooding, drought and water course pollution

Local and sustainable food

Supporting sustainable and humane farming, promoting access to healthy, low impact, local, seasonal and organic diets and reducing food waste

Sustainable materials

Using sustainable and healthy products, such as those with low embodied energy, sourced locally, made from renewable or waste resources

Sustainable transport

Reducing the need to travel, and encouraging low- and zero-carbon modes of transport to reduce emissions

Zero waste

Reducing waste, reusing where possible, and ultimately sending zero waste to landfill

Zero carbon

Making buildings energy-efficient and delivering all energy with renewable technologies


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