Post-occupancy study reveals how to really cut energy use in offices

One of the buildings studied in the research.

 Note: A version of this article appeared in The Fifth Estate on 21 March.

A new comparative study on the energy performance of existing office buildings has thrown light on the impact of tenant behaviour and the value of comfort.

Energy efficient buildings will only perform as intended with close collaboration between project teams, property managers and technical staff, a new study commissioned by Skanska, Go4Energy and Cushman & Wakefield has found.

The study analysed 20 office buildings in Poland, 16 of which hold LEED or BREEAM certification – meaning they are intended to be highly energy efficient.

By separating the energy consumption of tenants from the building’s total energy consumption, the research highlights the importance of tenant behaviour on performance.

Go4Energy analysed the energy use of the buildings and found that “the share of electrical energy consumed by tenants in the building’s overall energy balance ranged from 14 per cent to 65 per cent”.

The tenants have a significant impact on the energy consumption of the building and the electricity it consumes, dependent upon what type of tenant they are and the technological processes they use, which is why the share of electricity consumed by tenants varies so much.

The study is intended to make it easier to develop better, more targeted energy management systems for buildings in order to realise further improvements.

Waldemar Olbryk, director for support functions at Skanska, said the report was “a comparative analysis” between their buildings and other office buildings in Poland, and that no such study had been done previously.

“We looked at them in terms of their features, age and environmental specification,” he said.

One of the buildings studied in Poland.

The investor must care

The study found that the influence of the investor was a decisive factor in the designed energy performance of the building.

By supporting certification systems, the investor can achieve more than 30 per cent energy savings during the operational phase, meaning that the operating cost is reduced by up to £500,000 a year for the new office building studied in the report.

Certified buildings have a higher potential for energy savings due to the implementation of energy efficiency processes from the beginning, the report said.

But once completed and in use any further savings can only be made by the implementation of proper management processes.

The European perspective

European policymakers have identified the renovation of Europe’s inefficient building stock as a way to boost energy efficiency, as well as the economy. More than 75 per cent of European building stock is inefficient and the annual renovation rate across the EU is languishing at just one per cent.

The EU is currently revising its Energy Efficiency Directive, in order to put measures into law that will help it meet its UN commitments to cap global warming.

The European Commission’s bill is being amended by both the Council of Ministers and the European Parliament. Both members of the European Parliament and national diplomats must agree on an identical text before it becomes law. At the present moment Malta holds the six-month rotating presidency of the EU, and this is one of its priorities.

But leaked documents reveal that although member states will accept the executive’s proposed 30 per cent increase in energy efficiency compared to 1990 levels, they want them to be non-binding rather than compulsory.

Previously, in October 2014, EU leaders watered down the 2030 energy efficiency target to 27 per cent from a 30 per cent binding goal. Now, the Commission, which has vowed to put “efficiency first” in its energy policy, is arguing that the Paris Agreement justifies returning the draft target to 30 per cent.

Meanwhile, the European Parliament has backed resolutions demanding a 40 per cent binding efficiency target and is likely to call for greater ambition in the bill.

One of the results of the Polish study is a proposal to create a mechanism enabling the analysis of buildings according to the study’s methodology, which could help the wider European agenda.

There is a proposal to coordinate this project with the National Association for Sustainable Building Construction, which could bring huge savings across Europe, where the construction industry accounts for nine per cent European GDP and employees 18 million people.

Efficient buildings are evolving

The progressive areas of the industry are moving beyond where the EU leaders are debating, however.

Currently, the selling point for office buildings is around “performance based” comfort. This means the comfort level available for the user forms the basis of monitoring and verification by the management systems. The user’s working conditions, including ventilation, HVAC, lighting and so on are automatically adjusted and controlled.

With such buildings the most important goal is no longer to bring the greatest savings for the building owner but to provide a balance between the economics and the comfort and health of workers in the buildings.

Due to this trend, the definition of comfort is constantly expanding, in contrast to the traditional idea that there is only one factor (energy) that needs to be managed at the expense of others (for example, environmental quality of the internal atmosphere).

This is a valuable study that deserves translation into English (currently it is Polish only) and wider dissemination.

David Thorpe is the author of a number of books on energy, buildings and sustainability. See his website here.

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.