Why the measurable improvement in the use of energy in buildings remains elusive
Author: Kerry Mashford Date: 09/08/2013
Why does the UK building industry find it difficult to achieve the improvements in energy use suggested by the energy performance trajectories in successive iterations of Part L of the Building Regulations?
Improvements in energy use "scandalous"
Some people have described our performance in this area as "scandalous" and our ability to build low-energy buildings with low running costs is poor compared with some of our European neighbours. One critical issue is that there has been almost no attempt to close the loop from practice back into design. So, as regulations have become tighter, the difference between delivered and theoretical performance has tended to grow, largely because many of the factors affecting delivered performance have become more significant. The result is that, whilst theoretical energy performance of buildings has improved with successive revisions of the regulations, delivered energy performance has not kept pace.
Until very recently, almost no-one either knew about this problem or cared about it. Even fewer had any inkling of what to do to improve energy performance, other than the obvious action of turning appliances and devices either off or down. At best, some in the industry allocated limited resources to encourage cost-effective practices.
Energy improvement business case
The important first-step questions we need to ask ourselves are: What’s the business case for improving energy use? How much improvement in energy use (particularly savings) can be achieved for what cost?
In order to achieve a measurable improvement in energy use in buildings, we need to start by measuring the energy being used. Obvious, I hear you say and yes, it is. Surely a simple matter, I also hear you say, but unfortunately not! The mandating of sub-metering in non-domestic buildings as a result of the 2010 Building Regulations and the on-going roll-out of smart meters in the residential sector will revolutionise the measurement and monitoring of electrical energy use. These will not only make data collection easier but also possible over shorter time periods - for example, half-hourly in the case of newer non-domestic buildings. But, be warned, good metering architecture and sub-meter reconciliation are fundamental to the collection of useful data.
Assessing, measuring and monitoring energy use
CIBSE tools such as TM22 and DomEARM provide a framework for assessing expected energy use, taking into account the operational practicalities of a building and its unregulated uses. This can then be compared with the actual energy used in order to understand where it is higher than expected, and where to focus effort to improve it. Comparing results with benchmark data also has the advantage of providing a broader perspective of what’s ‘usual’ and ‘best practice’ in buildings of a similar type, size, use, etc.
Knowing where unexpected energy use is occurring leads to the next question: Why is energy use higher than expected? There are several structured approaches you can take to track down the root cause of variances in energy performance, and all are likely to call for more forensic investigations – for example, into fabric performance, air tightness, M&E system operation, occupant practices, etc. In the case of new-builds, fabric and system test results from completion and hand-over should already be available and can be used to help track down the root causes of unexpectedly high energy use.
In the case of an individual building, the approach involving measuring, comparing (with both the expected and the benchmarks) and root cause analysis can lead to establishing the size of energy improvement opportunities and an estimation of the cost of achieving them. Cost-effective improvements can then be prioritised. Continuous measurement or monitoring after the initial intervention helps maintain any positive impact and raises the alarm if energy use changes significantly – for example, because of a change in occupant behaviour or the degradation of equipment performance, etc.
All this may seem a lot of effort, but once it’s set up it’s no more onerous than any other continuous improvement programme. Even taking a very conservative figure, such an approach can reduce operational energy consumption in non-domestic buildings by between 25% and 30% - a prize well worth the effort for most building occupants.
Feeding back into design and delivery
Now we face the challenge of taking all this experience and practical understanding of building performance and feeding it back into the building design and delivery process. Currently, this is very, very poorly addressed and, as a result, most buildings are designed and then delivered in a ‘theory bubble’ – insulated from practice more effectively than the insulation installed in the buildings themselves!
Recently, some design practices have started to revisit past projects to undertake post-occupancy evaluations. However, energy use is only one element of this evaluation with the primary foci being architectural and occupant friendliness – both of which do impact on energy performance but only in a secondary way. However, with only a small number of design practices taking this brave step, it’s only a tiny drop in a very large ocean!
Open-source knowledge pool
The sector needs to establish an open-source knowledge pool of building energy pitfalls and best practices, continually updated from post-delivery measurement and monitoring. Such a resource would be invaluable for those involved in the design and delivery of buildings, closing the loop from practice into design. As a result, there’d be no excuse for NOT delivering a measurable improvement in the use of energy in successive buildings.