How Sustainable is a 'Sustainable Building' in Practice?

The first major review has been published of pioneering development One Brighton's performance against its challenging 2020 One Planet targets and show where it has succeeded and where it has failed over its sustainability targets.

One Brighton is a development by Crest Nicholson BioRegional Quintain LLP in Brighton, the coastal city south of London which has set itself the goal of being a one planet city.

The One Planet Brighton policy was decided on 18 April 2013 in Brighton & Hove by the local authority. As an evolution of BioRegional's One Planet Living philosophy the local authority approved a Sustainability Action Plan that would use BioRegional's methodology and embody the city's existing initiatives and climate change strategy, to be carried out by a wide-ranging partnership.

In this context, BioRegional worked with developers Crest Nicholson to develop an example of how this might work in practice with a development called One Brighton. This contains 172 residential units and 10,000 sq ft of office and community space on a former locomotive manufacturing site. The 0.39 ha parcel of land is close to Brighton train station.

The development has achieved an ‘Excellent’ rating under EcoHomes, a now-defunct national sustainability standard assessment for new homes, and was considered to be “Zero Carbon” under this assessment. Construction started in 2008 and the first residents moved in during 2009.

A post-occupancy assessment has now been completed to see exactly how well the development has performed against expectations. Was it really zero carbon? On the answers to this type of question hinges the performance of future buildings and developers should take note.

The developers are relieved to find out that One Brighton has significantly reduced lifetime greenhouse gas emissions, when compared to the average UK home, by 60%. However, its current emissions performance is not yet achieving design targets: its ‘as built’ lifetime CO₂e emissions are 53% higher than those of the
‘as designed’ model.

The gap is mainly because of the intermittent availability of the wood-pellet (biomass) burning boiler which supplies space heating and hot water. This has met approximately 30% of building’s heat and hot water demand, the remainder being supplied by natural gas.

If BioRegional’s target of meeting nine tenths of the building’s heat demand from biomass is achieved, One Brighton’s overall lifecycle carbon savings would be 78% lower than the average UK home’s (UK per capita CO₂e emissions = 9,122 kg/yr in 2011). This would be in line with achieving the (near) Zero Carbon target for operational emissions by 2020.

But under this assessment it's a good job that the EcoHomes standard is now defunct since it was clearly erroneous in its judgement.

One Brighton's sustainability features

Right: features of the building envelope and operational inputs affecting carbon emissions.
One Brighton was designed and is managed in a way to facilitate sustainable lifestyles. Design and management initiatives include:

• Only a very small number of parking spaces for disabled car users and shared car club vehicles, encouraging low levels of car ownership and use;
• Food-growing space on rooftop terraces, facilities for taking in deliveries of ‘veg boxes’ to individual apartments and a vegetarian café;
• Recycling and waste disposal initiatives (including the on-site in-vessel composting system for green and food waste).

The construction used a ‘green concrete’ frame containing blast furnace slag and an exterior wall made up of highly insulating clay blocks fired at low temperatures. Both features helped to reduce the building’s embodied carbon emissions, which came in 25% lower than for the average UK home.

Developer Crest Nicholson BioRegional Quintain set up an energy supply company (ESCo) for One Brighton to purchase electricity entirely generated from renewable sources. All owners/tenants sign an energy supply agreement with the ESCo. All of the electricity sold by the ESCo is backed by UK ‘Renewable Energy Guarantee of Origin’ (REGO) certificates issued by energy industry regulator Ofgem. This was a main plank of the near Zero Carbon strategy for the building devised at the outset.

One Brighton key lessons

The results of the one-year post-occupancy study have allowed comparison with the expected performance over its lifetime with actual performance to a limited extent. The report is honest about the conclusions, which also form recommendations for other developers attempting a similar kind of project:

• 67% of the buildings ‘as designed’ life cycle GHG emissions are attributed to embodied emissions and 33% are attributed to operational CO2e.
• Largest embodied impacts come from concrete in the floor slab, plasterboard and recurring impacts associated with painting and carpets.
• Largest operational impacts associated with energy consumption (REGO very low carbon grid electricity scenario) are due to gas backup for hot water and for the emissions associated with water supply and waste water treatment.
• Considering the model under a standard PAS2050 scenario (using UK average grid intensity) than the dominant emissions from electricity use come from appliances, cooking, white goods, refrigeration and MVHR (mechanical ventilation with heat recovery).

Pooran Desai, BioRegional ‘s cofounder who led the organisation’s involvement in One Brighton, said: “We’re really encouraged by the findings of this LCA, which shows the very low carbon fundamentals of this building are sound. But we are working to get greatly improved performance from the biomass boiler, to reduce operational emissions significantly and take us to our 2020 target.”

The life cycle analysis was conducted by eTool, whose director, Patrick Hermon, observed: "An LCA never fails to raise interesting design questions surrounding not only material selection but operational energy, water, transport, waste and functionality. This LCA of One Brighton is no exception, particularly thanks to the transparency of the developers and post occupancy monitoring - an important step forwards in closing the performance gap.

"The LCA will also be compliant with international standard EN15978. This methodology (also broadly used in BREEAM LCA credit criteria) standardises the LCA process and verifies the environmental performance benefits claimed within the LCA given the upstream data used, the methodologies applied and the documentation provided. A complete EN15978 report will be completed very soon."

It concentrates mainly on factors associated with the building itself, including materials, assembly, maintenance, transport of materials, operational energy use and end of life disposal. But there are other factors that would significantly influence the total LCA CO₂e emissions of the designs, to which the developers should take at least some responsibility, including:

• Personal transport of the occupants;
• Impacts associated with foods, goods and services (purchases made by residents, clothes leisure activities etc);
• Impacts associated with occupant waste and recycling;
• Embodied impacts of non permanent building fixtures such as furniture and appliances;
• Embodied impacts relating to building planning and sales.

These factors listed are considered out of scope of the LCA but nevertheless warrant declaration.

The main conclusion in general terms is that developers should beware of declaring that a development is zero carbon, and that there continue to be difficulties in achieving anything like this in practice. All credit to the developers in this instance to taking the trouble to examine their building's performance. If only more developers were to do the same.