Getting real about energy use

CarbonBuzzz, design energy use

Design energy use and actual energy use are, usually, very different. An online tool now makes it possible to make comparisons, as Ken Sharpe describes.

It is widely known, even accepted as the norm, that the actual energy use of buildings exceeds, even far exceeds, what they were designed to use. But even if you know the difference for a building that you were involved in designing, you probably don’t know how that difference compares with other similar buildings. That is one of the questions that the latest development of the CarbonBuzz online tool addresses.

Legislation to reduce the energy consumption at design stage tends to favour complexity and have a disconnect from how buildings are actually used and run. How a car is driven can produce fuel-consumption figures very different from those published — and the same applies to buildings.

Indeed, there is growing evidence that legislation is not achieving the expected reductions in the actual energy use of buildings — and could even have significant unintended consequences. Large portfolio holders, in particular, are taking notice of the commercial risks associated with ‘low carbon’ buildings and refurbishments falling short of expectations.

CarbonBuzz aims to encourage users to go beyond compliance with mandatory Building Regulations and refine estimates to account for additional energy loads in operation. Users can compare design energy use with actual energy use to help them close the gap between design and operational energy performance.

What is apparent from around 400 projects that have been uploaded to CarbonBuzz is just how much actual energy use exceeds predictions. On average, buildings consume 1.5 to 2.5 times more energy than the design value.

One aim of CarbonBuzz, a free resource, is to ‘get real’ about building energy consumption and help participants close the gap between calculations and actual building performance. You can look at the site and get involved using the link at the foot of the page.

Dr Judit Kimpian of Aedas, which led the development of the CarbonBuzz tool, explains that it makes possible the tracking of data over time, from new build to refurbishment, so that it becomes possible to understand year on year what is happening.

The project is supported by CIBSE and RIBA, and the latest development was funded by the Technology Strategy Board. CIBSE’s technical director Hywel Davies says, ‘CIBSE welcomes the collaborative industry-wide focus of the initiative, as well as its ability to help develop understanding around the gap between predicted and operational energy use. We are encouraging architects, engineering and building-services designers to upload their projects.

‘The aim is to give quick and simple answers. The more you put in, the more you get out. Even very simple data will give comparisons with other building types and hints on how you might improve.’

All kinds of people can participate — such as engineers, facilities managers, architects, local authorities, managers of Government portfolios, developers, landlords and investors. It is very quick and simple to upload, share and benchmark data — using, for example, CIBSE energy benchmarks. The performance of buildings can be compared against that of other similar buildings, anonymously if that is what the participant wants to do.

Those who want to go further can publish case studies to showcase their expertise.

One person who is very supportive of CarbonBuzz is Justin Snoxall, head of British Land’s business group. Out of five developments completed since 2009, there is only one for which design and operational performance has been compared — 201 Bishopsgate in London. He explained at the launch of CarbonBuzz, ‘It may seem odd or even perverse, but currently we as an industry do not use a common tool to compare design and operational performance in buildings.’

The benefits of comparing design and operation have been demonstrated by a review at 201 Bishopsgate in London.

The comparison between design and operations performance was made possible by funding from the Technology Strategy Board and has, says Justin Snoxall, ‘been a powerful illustration of the benefits of comparing design and operation’.

One of outcomes of this review was highlighting the value of installing integrated metering between base build and occupier fit-out. It took a long time to achieve, but has been crucial to understanding energy use.

The review also showed how BMS optimisation processes introduced over the last four years have been important to saving substantial energy. Indeed, the operational regulated energy use of 201 Bishopsgate is in line with design predictions.

BMS optimisation has been found by British Land to be effective in achieving substantial energy savings in new buildings. Better management of M&E services in its buildings has seen an average 30% reduction in energy for landlord services over the last four years.

Another discovery was out-of-hours energy consumption in 201 Bishopsgate, which was not considered at design, being a significant proportion of the total.

And a problem that is widely experienced was for the electricity used for small power and ICT being much greater than the design prediction. This appears to be a common problem in design, which would become more apparent if there were more studies of design and operational performance.

An all good reviews should throw up more than they were designed to. In this case it was identifying where more energy could be saved by investigating chiller operating hours and winter operation.

Looking ahead, the CarbonBuzz platform will contribute to a comprehensive database of forecast and actual energy use of buildings in the UK. It will also help to understand energy consumption beyond regulated energy and how best to reduce actual carbon emissions.

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