Taking control of building performance

Andy Lewry, controls, BMS, BEMS, energy efficiency, performance gap
Even choosing the correct controls are chosen does not necessarily guarantee performance — Andy Lewry.

The control of energy in buildings is generally poor, and the performance gap can inflate energy bills by up to 400%. Andy Lewry discusses how controls can help.

Building controls, whether stand-alone units or full building energy management systems (BEMS), are designed to provide a comfortable climate for building occupants while consuming the lowest possible amount of energy. I have previously published a guide (‘Understanding the choices for building controls’ [1]) that provides simple explanations of various types of controls, what they can do, and where and why they can and should be used — the pros and cons, and how to achieve an effective solution in practice.

However, even choosing the correct controls are chosen does not necessarily guarantee performance. The performance gap (2) shows an operational performance difference of 150 to 400% between the design and the building in use.

This presents asset and facilities managers with a unique challenge in the context of continuing concerns over resilient energy supplies, and increasing levels of statutory obligations connected to emissions and climate-change policies. The reality of the situation is that the business may not always prioritise investment in energy-saving measures, and any business case needs to be robust, taking into account reduced maintenance and increased productivity. Such factors will minimise risk to the owners by protecting the asset and, if the building is rented out, ensure high rental values and low void times.

In addressing risk to the business, the ‘do-nothing’ scenario should be considered first. However, in light of increasing energy prices and security of supply issues, this is not a realistic option. Increasing prices can have a dramatic effect on the cost base of organisations, leading to reduced competitiveness and a need for a drive for greater efficiency. Security-of-supply issues lead to the need to protect essential services, such as installing onsite generation to protect servers and prevent potential loss of data. To mitigate these risks, organisations need to understand how they use their energy and then manage it (3).

A new guide on energy management (4) from the Institution of Engineering & Technology (IET) concludes that modern building designs are normally governed by building codes which require an overall building energy performance that can be achieved by passive design, and the use of low carbon technologies and renewables. Sustainability design tools such as the Building Research Establishment Environmental Assessment Method (BREEAM [5]) help shape new installations and refurbishment projects. ‘Performance-gap’ issues will probably arise if handover, operation, maintenance and commissioning issues are not considered, and the use of assessment methodologies such as BREEAM-In-Use will help.

The guide also concludes that for successful energy management you cannot just turn off services — because for a business to operate successfully it is essential to provide staff with conditions that promote efficient and effective working practices. People are energy management’s biggest and best resource, but if badly managed can also be the biggest obstacle. Technology is only an enabler, and for energy management to really work the management and staff need to be on-board.

Site induction, education, training, feedback and updates will all assist. Directors should champion energy management and associated initiatives, managers should own the procedures, and users need to be incentivised.

In achieving this, controls, because of their proved effectiveness should be one the first things taken out of the toolbox. The impact, in practical terms, is that the design of such systems is generally very good and commissioning is acceptable. However, the understanding and operation of such systems at the user level is generally poor. As a result, the need to maintain these systems to realise the ongoing saving potential is not generally recognised by the end-user and/or the engineering-services provider, which often means the systems are not maintained to the level required. In addition, the settings are not reconsidered and revised when significant changes occur to the building or how it is used.

Building management systems (BMSs) and building energy management systems (BEMSs) are powerful tools in ensuring that buildings are run efficiently and provide the desired environment for the occupants (6). As technology becomes cheaper and advances more rapidly, control systems need to be flexible, upgradable and have the facility to easily communicate and integrate with other systems.

However, care needs to be taken in their operation, and staff using the system need to be fully trained. Ongoing commissioning and preventative maintenance need to be carried out to ensure the potentially large energy savings are realised, operational costs are controlled and expensive failures do not occur. End-user needs should be taken into account, and staff training and awareness raising should be carried out to get the building’s occupants involved.

Andy Lewry, controls, BMS, BEMS, energy efficiency, performance gap
People are energy management’s biggest and best resource, but if badly managed can also be the biggest obstacle.

Dr Andy Lewry is a principal technical consultant in the BREEAM Existing Buildings Team and author of briefing note, ‘Energy management and building controls’, on which this article is based. The full publication is available as a free download from http://www.bre.co.uk/energyguidance.


1. Lewry, Andrew J. Understanding the choices for building controls. BRE IP 1/14. Bracknell, IHS BRE Press, 2014.

2. Lewry, Andy and Hamilton, Lorna; Finding the performance gap, Modern Building Services, Vol. 14, No. 2, pp 12-13, June 2017.

3. Lewry A J. Energy management in the built environment: a review of best practice. BRE FB 44. Bracknell, IHS BRE Press, 2012.

4. IET, Guide to energy management in the built environment, July 2017, ISBN: 978-1-78561-112-4, http://www.theiet.org/resources/standards/em-guide.cfm.

5 http://www.breeam.com

6. Lewry, Andrew J. Operating BEMS — A practical guide to building energy management systems. BRE IP 2/14. Bracknell, IHS BRE Press, 2014.

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