Energy use in buildings – contributions and considerations in urban systems

Author: Kerry Mashford 09/08/2016

With more than half the global population now living in urban areas, one of the key issues confronting us today is how we make our growing cities sustainable. A new hardback book 'Sustainable Cities' offers valuable insights for addressing this vital challenge. It evaluates our urban environments and assesses the progress that is being made towards achieving cities that are sustainable. Reproduced here is the chapter on energy use in buildings, written by our Chief Executive, Kerry Mashford.


The achievement of truly sustainable urban environments depends on the sustainability of the individual elements that make up a town or city as well as how these elements work together to create effective and sustainable urban systems. The collective contribution of buildings on the energy demands of a city represents usually the largest and most difficult to manage component. Whilst buildings impact upon sustainability in many other ways, energy performance is a reasonable proxy for overall sustainability and hence this chapter focusses on the energy performance of the new and existing buildings across Europe. It explains how we have been deluding ourselves for many years about their true energy efficiency, illustrated by examples from current large scale studies, and explains what is happening to address this at European Union (EU) level and in individual member states.

It introduces some of the schemes and metrics used to measure and demonstrate the energy performance and overall sustainability of buildings, together with tools and techniques coming into more common use to test, verify, and benchmark both the intrinsic performance of a building (its fabric and services) and the energy consumed (and in some cases generated) in its operation. 

For existing buildings which in Europe in 2050 will still make up the majority of built stock in our towns and cities, the chapter considers what can be done to improve their energy performance, taking into account the social and financial circumstances of building owners and occupiers, including giving some inspiring examples of what is known as deep retrofit.

The chapter concludes that by adopting an approach to construction and refurbishment of buildings in which practice is informed by measured performance, we can dramatically improve the energy performance of buildings and their consequent energy burden on urban areas, reducing impact on local and global climate and leaving a much more manageable task for energy supply systems.

The complete Sustainable Cities hardback book is available from the publisher I.B. Tauris.

Buildings in city systems

At some time between 2008[1] and 2010, human population distribution passed a very significant tipping point: for the first time in history more than half the world’s population now lives in towns and cities and this wave of urbanisation is continuing.[2] As the world’s population continues to grow from just over 7 billion currently to a projected 9 billion by 2050, both the number of people living in urban areas and the proportion of the total population living in towns and cities will increase further. By 2050, the World Health Organisation projects that the urban population will reach 6.4 billion, representing 7 out of every 10 people.[3] If society is to continue to function; if human beings are to have relatively healthy and comfortable lives; if we are to have any hope of continuing to live within the resource constraints of a single planet then we have no option but to apply our best minds and our best efforts to innovating and adapting our collective lifestyles to live within our means. City systems, already the most impactful contributors to resource use, will become ever more significant as population and urbanisation grow.

The concentration of human activity in cities leads naturally to some resource efficiencies, most significantly in terms of transport, as distances travelled and comparatively high public transport use increase per capita efficiency. The benefits of densification are less significant for buildings, in part because major cities especially are host to substantially greater numbers of prestige offices, hotels and public buildings than prevail elsewhere. Prestige city buildings tend to have disproportionately high energy use – a topic we will return to later.

Figure 1.1 - Final energy use by sector EU28, 2012 figures

Across Europe, final energy use in buildings accounts for 39% of total energy consumption - residential energy accounting for 26% and non-domestic (or services in Figure 1.1) for 13%. Within the non-domestic buildings category, more than 50% of energy use is for offices, retail and wholesale trade (Figure 1.2). Whilst non-domestic buildings account for a smaller overall proportion, their energy use per square metre, or ‘specific energy’, is on average about 40% above that for residential buildings and is growing at a faster rate. In cities the specific energy of non-domestic buildings is greater still, compared with residential buildings because residences in cities are generally smaller than in less densely populated areas and a greater proportion of non-domestic buildings can be classified as ‘prestige’, having particularly spacious public areas and being highly serviced.

Figure 1.2 - Energy breakdown in non-domestic buildings

Cities also suffer from the ‘heat island effect’, where waste heat from transport, cooling systems and human activity combines with space heating leakage from buildings to raise the ambient external temperature. In temperate regions this leads to an increase in use of air conditioning, which in turns adds more waste heat to the surroundings, creating a vicious cycle. Add to this a rise in ambient temperature as a result of climate change and many experts now predict that, within the next 20-30 years, night-time cooling of building fabric, roads, plazas and pavements in cities will not be sufficient to restore the city to an acceptable temperature for the beginning of the next day. There is the danger that city systems will become thermally unstable, unable to moderate their temperature effectively with the current mix of buildings, their fabric performance and services. If left unchecked, city infrastructure will fail, city dwellers, workers and visitors will suffer heat stress and, emergency services, deprived of functioning power, water, transport and information infrastructure systems, will be overwhelmed and unable to respond.

With buildings collectively representing the largest contributor to energy use and emissions, and knowing just how great the potential is to improve them, there is every reason to address this from all possible angles. Making sure that every new building added to the stock contributes as little as possible to the growing problem, and ideally reduces the problem through being energy positive and carbon negative [4]  is one course of action – but knowing how well new buildings really perform in terms of energy is critical to improving the delivery of intrinsically energy efficient buildings. Buildings that perform well from an energy perspective also tend to be those that use water more efficiently, have better indoor air quality and thus provide a good internal environment for living and working. A large number of sustainability assessment schemes have been developed across the world to capture these and other factors, such as biodiversity, ethical procurement, embodied energy. Some are more widely adopted in Europe and their respective merits are discussed in many studies.[5]

We also need to focus on upgrading our existing stock. An estimated 60% of the buildings that will be standing in 2050 [6] have already been built, with 40% of current domestic stock across Europe having been constructed before 1960 when energy-related building regulations were in their infancy. This represents not only a challenge but also offers potential for individual and societal benefits, extending beyond the obvious ones of cost and comfort. Whilst there is debate amongst the governments of the European (EU) member states about the realistically achievable target for energy efficiency savings from existing buildings, the Building Performance Institute Europe [7] estimates that up to 71% energy savings can be achieved through refurbishing our existing buildings, bringing opportunities for economic development as the refurbishment sector grows in size and capability.

The final piece of the jigsaw is improving the ways buildings are operated, be they complex or simple, domestic or non-domestic, occupied by owners or tenanted. Internal studies by major property companies have shown that, even in a prestige headquarters office with a very good energy and sustainability certification, 20-30% energy improvement can be achieved through recommissioning and better operational energy management. And if one needed any more convincing, studies comparing the cost of investment in electricity generation with investment in improvements to energy efficiency in buildings show that it should be quicker and cheaper to improve our buildings than to build new power stations.[8]

What is the composition of building energy use?

The energy used by buildings comes from two main demand generators – the intrinsic performance of the building and the energy demands arising from the use of the building. In most recent practice, these are now increasingly offset by an energy contribution from building integrated power generation and thermal exchange systems.

To take these in turn, the intrinsic performance of the building is determined by the fabric performance of the envelope and the energy required to run the basic (regulated) plant and equipment comprising the building services. In the limit, once a building is constructed, there is rarely any need for additional energy to keep it standing up!  But, to be useful as a building, a comfortable indoor environment needs to be maintained and this requires heating, cooling, ventilation and other services. The intrinsic energy performance of a building is therefore determined on the assumption that a standard set of internal conditions is maintained, taking into account varying external conditions. This is similar to the practice of reporting fuel economy and CO2 emissions performance for cars on the basis of a standardised test circuit.

But, just as no one expects to drive their car according to the strictly controlled conditions determined by the standardised test cycle, neither should we expect buildings to be operated according to the standard assumptions used to arrive at their predicted energy demand. This brings us to consider the energy demand determined by the way occupants use the building, which again can be considered to comprise two main sources. Firstly, the internal conditions desired by particular occupants may differ significantly from those assumed by the standard assessment method: occupants may prefer a higher or lower indoor temperature, may choose to leave windows open even when the outside temperature is low, take far more showers or have deeper baths that the basic model assumes. These would all have an impact on the regulated loads – those considered as part of the intrinsic performance. In addition, a wide variety of activities can take place in buildings and many of these use energy – these are termed unregulated loads. Devices and appliances that are plugged in constitute the bulk of this additional energy requirement and are frequently referred to as ‘plug loads’ or ‘small power’. Whether we consider the effect occupants have on the regulated or unregulated loads it is clear that occupant behaviour, specifically the way occupants interact with their building and its controls, can have a very substantial impact on the total energy demand.

Figure 1.3 - Indicative composition of actual energy use compared with predicted energy use

Building Certification

So how do we go about assessing and certifying buildings in terms of their energy performance? Across Europe, the promotion of energy efficiency in buildings is the purpose of the EU’s Energy Performance of Buildings Directive, with which all member states must comply. When the Directive was first implemented in 2002, its focus was on CO2 emissions but it has since been refocused on energy efficiency, with energy intensity[9] being the primary metric and an objective to deliver ‘nearly zero energy buildings’ from 2020 onwards. The Directive includes energy used for space and hot water heating, cooling, ventilation and lighting (i.e. regulated loads) in both new and existing domestic and non-domestic buildings. Whist the Directive requires all member states to implement assessments of energy performance, set minimum standards of energy performance in buildings and provide independent oversight of energy performance certificates (EPCs) and reports, it does not mandate the methods used or the minimum standards required. However, it does oblige each member state to establish methods of assessment, reporting and enforcement, in accordance with the requirements of the Directive. Hence, whilst the Directive is EU wide, its interpretation and implementation differs between countries within the EU.

Figure 1.4 - Typical EPC certificate issued in England and Wales showing current and potential energy rating and environmental impact

Without exception, all EU member states require the energy performance of new buildings to be assessed at the design stage using approved modelling and calculation methods (and increasingly this is also being adopted for major refurbishments), resulting in classification of ‘as designed’ performance, usually in terms of kWh/m2.yr, although in some states CO2 emissions are also used. Although in 2015 the UK government abandoned its commitments to zero carbon standards for new buildings, there is still a significant focus on improving the performance of new-builds, both domestic and commercial. The UK government is now focussing on energy as well as carbon and has confirmed its commitment to the EU Energy Performance of Buildings Directive (EPBD) of 2010, which requires all new buildings to be "nearly zero energy" from 1 January 2021 As energy and carbon dioxide are not directly interchangeable indicators persisting with both could cause additional complications for the UK.[10]

Only in Sweden is it currently required to provide building energy certificates for all new buildings, based on actual energy consumption, this being based on measurements made during the second heating season of the building.

Figure 1.5 - Swedish building energy certificate from 1 Jan 2014

One might expect that being able to differentiate buildings on the basis of their energy performance would be a significant source of competitive advantage for the building owner at rental or sale and also for the designer and specialist consultants involved in the design. Indeed, if followed through into verified performance in practice, such advantages would also accrue to the main contractor and specialist subcontractors. There is some evidence that buildings with a high energy performance are beginning to enjoy a competitive advantage, although this still tends to be more attributable to the building’s overall sustainability rating (e.g. BREEAM Excellent) and associated prestige status than to the energy efficiency of the building. In many cases the causality is reversed in that only a prestige building that is expected to attract high rental income is thought to warrant the incorporation of the many and various sustainability credentials that enable it to be classified as BREEAM Excellent or LEED Platinum.

Much of the focus for debate in relation to the Energy Performance of Buildings Directive has been on determining what constitutes ‘nearly zero energy buildings’ and how to achieve this by 2020. Little attention was given initially to the fact that the objective is to deliver ‘nearly zero energy buildings’ not just to deliver buildings designed to be nearly zero energy. This is a very different matter.

In practice, this ‘design based’ certification is rarely faithfully translated into physical buildings that perform as predicted. Studies undertaken in the UK on behalf of Innovate UK [11] across almost 50 new non-domestic buildings and approaching 4000 new dwellings, are providing initial indications that energy ‘in use’ is typically between 2 and 4 times that predicted, and often considerably higher [12], taking into account unregulated loads.

Figure 1.6 - Examples of buildings being studied under Innovate UK’s Building Performance Evaluation Programme 

Similar findings are emerging from many other studies to the extent that the frequency and extent of the discrepancy between predicted and operational performance, in terms of energy use and other parameters, is becoming more widely recognised and is now referred to as ‘the performance gap’. The factors that contribute to this performance gap, their relative magnitude and how they can be eliminated or reduced is a major focus for research and for the development of tools, methods and improved practice. In part following from the Innovate UK studies mentioned above, the Zero Carbon Hub in the UK was tasked with conducting a major study involving an extensive breadth and depth of industry stakeholders. It published its evidence report in March 2014 in which the various contributing factors are explored.[13]

Having raised a client’s expectations by producing a building design with exemplary theoretical performance, failure to realise this in practice could have far reaching consequences, not least loss of competitive advantage and a potential backlash against aspirationally good design. A study by the Better Building Partnership [14] showed almost no correlation between the operational energy intensity in use and that predicted at design.

Figure 1.7 - There is almost no correlation between EPC ratings and actual energy intensity (Credit - Bill Bordass & Better Building Partnership)

Whilst some proportion of the performance gap can be attributed to assumptions and approximations in building modelling, one of the main sources of the performance gap is the realisation of the building – the translation of the design into contractual requirements and subsequently into physical form. This realisation is subject to ‘accidental’ design changes arising from product and material substitution, poor buildability of the design details, lack of precision in construction and poor understanding of the consequences of decisions taken on-site, all compounded by failure in the communication of design intent. In projects that have taken great care to eliminate these sources of divergence, the performance gap has been significantly reduced or even eliminated. It remains a major shift of culture and practice to roll this out across the construction sector.

Figures 8a and 8b - Comparison between a traditional cold roof eave junction and a timber frame warm roof eave built using a roof cassette. It is virtually impossible to construct a traditional eave with mineral wool quilt as shown in the drawings – which leads to cold bridging and air movement at the junction

Failure to commission building services and systems correctly and configure them for the specific situation also contributes significantly to the performance gap since this results in a deviation from the designed operating regime.

Quality assurance, ‘in process’ testing and inspection regimes during construction typically fall far short of those found in other ‘manufacturing’ sectors. Food and drink; automotive; domestic appliances – whatever one can bring to mind, is manufactured using assured processes with testing of the product at various stages of manufacture, with auditing and feedback loops into product and process improvement – but not so for most buildings. In some EU countries we test and certify the air tightness of a building at completion but that is about the extent of it: ‘in process’ inspection is largely focussed on safety and structural integrity and is often cursory in other respects.

In the UK, developers are required to complete and submit an ‘as built’ SAP [15] assessment, but SAP assessors are usually remote from the construction process of the building so do not capture even the deliberate, well-considered design changes that occur during construction, let alone the accidental ones. Consequently, the ‘as built’ SAP is usually a re-run of the ‘as designed‘ SAP with only airtightness figures updated to reflect the constructed building. Apart from not representing the ‘as built’ building, this failure to test and verify the performance of buildings adequately, capture the details of what was actually built, revise performance predictions accordingly and feed back the measured performance to design, means that there is little individual, corporate or sector learning from the process and hence the benefits of this well-intentioned requirement are not obtained. Better, faster, simpler testing methods such as the rapid air tightness testing method ‘PULSE’ developed by University of Nottingham and others is an example of a tool that could make ‘in process’ and completion verification testing more effective and informative [16].

This places a continued and growing burden on the infrastructure of our towns and cities further exacerbated by the urban heat island effect and, as these new buildings join the ranks of ‘existing’ buildings, we perpetuate the need for deep refurbishments of those existing buildings. In summary then, it is vital that we not only improve our collective ability to design low, zero or positive energy buildings (those that contribute energy to the grid), but that their delivery is ensured through the application of knowledge and effective processes – we must not delude ourselves that low energy design is the end of the job. The knowledge and skills to connect these various factors will be increasingly valuable in Europe and across the world as population growth increases pressure to create viable new ecosystems combining both natural and anthropogenic resource flows.

Buildings in use

Addressing the design and delivery of a building is but the foundation of energy efficient operation. In the early years of its life, main contractors (and perhaps sub-contractors and designers) may continue to have some involvement with the building, for example through the defects period and, if good practice is followed, as part of a ‘soft landings process’[17] and/or by undertaking seasonal commissioning to ensure the building systems can be configured and have settings established for all seasonal conditions. After a building is two or three years old, however, contact with those who brought it into being falls away and the building owners or occupiers are on their own.

Building owners and occupiers have diverse motivations for improving the energy performance of their buildings, be it through energy efficiency and/or through generation. For owners and tenants of prestige properties one of the primary considerations is the environmental credentials of the building which reflect on the reputation of the corporate entities involved, in turn influencing their customer base, business relationships and the attraction and retention of staff. The US Institute for Building Efficiency summarises results from a number of studies investigating the primarily financial benefits of green buildings with good energy performance.[18] Parameters include tangible financial measures such as resale value, rental rates, occupancy rates, operating expenses and operating income, plus some less tangible ones such as productivity gains. In all of the tangible metrics green buildings outperformed buildings with no certified environmental performance with the benefits in more recent studies being greater than those in earlier studies. In the UK however, a study by Fuerst, F., McAllister, P. and Ekeowa, B, of which initial findings were published in 2011, shows little correlation between environmental certification and financial metrics. [19] The Energy Act 2011, which will make it unlawful after 2018 to rent out residential or business premises with F and G (EPC) ratings will begin to focus business motives as we approach the deadline. After the deadline, there may be different consequences such as less legitimate movement of tenants in and out of poorly rated properties, with ‘informal’ or black market property rental blossoming.

Figure 1.9 - Examples of test equipment used in building performance evaluation. Source: NEF

For all commercial owners and tenants, the monetary cost of energy is important, but, even though this may well be large by domestic standards, the larger the company concerned, the less financially significant the operational building energy tends to be; so building energy improvements will be driven by different motives – legislation, security of energy supply, reputation and, eventually, simply that this is the way things are done when buildings are procured, refurbished and managed.

For domestic owner occupiers, energy costs, whilst significant, may not be sufficiently compelling to drive investment in energy improvements: if an owner occupier can afford the energy they are using, any potential investment in their home is more likely to be spent on home improvements for which they can see more immediate benefits (such as a new kitchen or bathroom) than explicitly in improving the thermal performance of the fabric of the property. Conversely, for those struggling to meet their energy bills, there is no money to pay for investments of any kind, so the home owner will continue to live in a poorly performing home in as much comfort as they can afford until and unless external help is offered.

The link between poorly performing homes and individual and societal health has long been acknowledged but, until quite recently, not measured or subjected to cost benefit analysis that could justify investment from public funding to offset the cost of dealing with ill health, crime, antisocial behaviour, unemployment and even remedial education. Research by Alice Jones on behalf of Nottingham City Homes [20] is one recent example of work aimed at quantifying the health and societal impacts of improving homes, individually and at a community scale. It is clear that the true costs of poor quality, energy inefficient housing is not fully recognised and, until this changes, the funding to invest in improvements on behalf of those unable to pay for it themselves will not be reallocated from other parts of the public purse. We will continue to tackle the symptoms, rather than the cause.

Reducing operational energy use – metering, monitoring and benchmarking

Notwithstanding these different circumstances and drivers, there is a growing interest in better energy efficiency, with initiatives, legislative and market requirements, and an increasing choice of mechanisms by which building owners and occupiers are able to monitor over time both the total energy used in their buildings and its disaggregation by end use.

In several EU countries this is helped by a requirement to meter energy by end use, and by tenant (in a multi-tenanted building). However, evidence emerging from studies investigating the implementation of the UK’s sub-metering requirements for new build which is expected to be published after Innovate UK’s Building Performance Evaluation programme is complete, reveals that whilst meters are being installed, the metering strategy rarely reflects the subdivision of space or use and is almost never properly commissioned or reconciled, hence leading to very poor quality data. This is a lost opportunity and currently just adds to the capital cost of the project without providing beneficial information. If intelligently designed and configured and correctly reconciled, sub-metering can provide a high level of granularity in energy use. If this is then analysed using a tool such as CIBSE’s TM22 [21], it can identify unnecessary or unintended demands on energy and target improvements accordingly. Examples of this include lighting being switched on automatically when not required or heating ‘fighting’ air conditioning. As building owners and occupants are beginning to recognise the value that correctly configured sub-metering can deliver, reports are emerging of contractors being challenged to revisit sub-metering installations, correct them and reconcile the meters.

At a much more aggregated level, annual energy use can be captured through fiscal meter readings and used in benchmarking. Benchmarking websites are springing up across the EU and elsewhere, that allow the user to compare their own building(s) against a portfolio of anonymised buildings, filtered to comprise only buildings of similar type and use. Carbon Buzz [22] is one such tool. In some large corporates for which environmental performance is a company value, league tables of the company’s own buildings’ energy performances are being introduced, coupled with exchange of best practice across the corporation. For leading commercial landlords, the separation of landlord and tenant energy use is important so this level of disaggregation is being adopted.

In order to comply with the EU Energy Performance of Buildings Directive, in any building over 500m2, whether publically or privately owned, an energy certificate not more than ten years old must be displayed in a prominent position. There is no stipulation as to whether these certificates are arrived at using theoretical energy performance data or measured data and different member states have interpreted this requirement in different ways. For example, in the UK, Norway, Sweden and in Belgium energy performance certificates, based on measured energy use are required to be displayed for public buildings over a certain size and some non-public buildings are also adopting similar displays to illustrate their (usually good) energy performance. In the UK, the Display Energy Certificate (DEC) is based on measured data with the requirement that larger public buildings (those over one thousand square meters) renew these certificates each year. Also in the UK, for all other buildings that are the subject of a transaction such as sale or lease agreement, an energy performance certificate (EPC) based on the characteristics of the building, but not including the measured energy use, must be produced and provided to the potential purchaser or leaseholder or tenant.

Although not mandated, it is encouraging to note that some commercial organisations at the leading edge of energy performance are beginning to disclose publicly the energy use of their buildings, sometimes in real time, on the basis that this will make business sense to them in a number of ways – reputation, cost savings etc. In the US, the state of California is leading the implementation of this practice, having enacted an energy use disclosure programme in 2007 for non-residential buildings which, from 2014 onwards, requires building owners and occupiers to report actual energy use using the Environmental Protection Agency’s Energy Star Portfolio Manager System [23]. In the UK, Carbon Culture [24] provides a platform for building owners and occupiers to disclose their building energy use from a rolling average based on metered data. Other tools are being made available, often by not-for-profit bodies, to provide building owners and occupiers with the means not only to track their overall energy use, but to benchmark this against others, disaggregate the end uses of energy and to support individual initiatives to improve energy efficiency.

The Green Construction Board in the UK (convened by the UK Government) has recently commissioned a study into ways and means to encourage building owners and occupiers to pay greater attention to measuring and reducing their energy use through reporting mechanisms, benchmarking and associated tools.[25] At a city level, at the time of writing, the Greater London Authority is formulating a project to promote and enable energy disclosure amongst its business constituents. The National Energy Foundation has been working with Legal & General, a major owner of commercial property, and with Building Energy Solutions to devise VolDEC, a landlord/tenant energy use measurement and benchmarking system which, having been piloted on 16 commercial multi-tenanted office buildings, is now being made available more widely.[26] So, at many scales there is growing activity as building owners and occupiers see the business benefits of improving the use of energy in their buildings.

Metering and monitoring devices, benchmarking and analysis tools provide the means to find out how well a building performs in comparison to its peers and where to target efforts to improve energy use.

With 60% of Europe’s 2050 buildings already in existence (up to 80% quoted for the UK) the energy efficient upgrade of the built stock represents the largest infrastructure challenge we face in relation to achieving a sustainable future. However, just as we have demonstrated above how easy it is to design for good energy performance and then fail to deliver that performance, the same applies to retrofit and refurbishment. Effective refurbishment at scale requires a professional approach, establishing the pattern of energy use before refurbishment, validating the improvements made to building fabric and services in the course of the refurbishment, and verifying the delivered performance through measurement and monitoring. As is recommended for new build, capturing process improvements successively to improve the effectiveness of refurbishment is essential if we are to make headway towards achieving the 71% reduction in energy use (cited earlier) among Europe’s existing buildings.

For some of the stock however, in particular poor quality housing, we must recognise that reduction in energy demand following refurbishment will be less than expected from the improvement in building performance, and may even be zero. This is because the benefit of improving energy performance will result in occupants being more comfortable for the same energy use, rather than reducing their energy demand. For these occupants, the primary benefit will justifiably be in improved quality of life.

In contrast, there are individual home owners committed to improving their own building energy and CO2 emissions. The SuperHome network [27] is a community of such individuals, known as SuperHomers, who have succeeded in reducing their domestic CO2 emissions by at least 60% and are willing to share their knowledge and experience with others through open homes events and web exchanges (Figures 1.10 and 1.11). Since the creation of the SuperHomes network in 2007 others have been formed and a federation of such networks has recently been established. Reports indicate that householders are inspired to take action to improve the energy performance of their homes and many of their fears are allayed by visiting homes that have been so improved and discussing practicalities with the owners.

Figures 1.10 and 1.11 - Birmingham and Camden SuperHomes. Photos courtesy of

Maintenance and operation

Building maintenance plays an often underestimated role in determining overall energy efficiency and hence energy demand.  Maintenance of building fabric is important to maintain air tightness, thermal efficiency and the overall condition of the building fabric which in turn has consequences for occupant health – for example excess humidity causes mould growth. Lack of fabric maintenance tends to be more noticeable than neglecting the maintenance of services – there is a tendency to take the view that ‘if it isn’t broken, don’t fix it’.  However, services, being on the whole energy using devices, have a direct impact on energy demand – a freely rotating bearing takes much less energy to move than a worn bearing, and hence poorly maintained building services plant uses much more energy. The US Institute for Building Efficiency summarises studies with impacts typically above 20% and on occasions up to 60% for specific plant and equipment [28]. Poorly maintained services often continue to use excessive energy for months, even years, before failing, often catastrophically. Another opportunity is then lost as replacement equipment has to be sourced quickly as a ‘distress purchase’ and thus the purchaser fails to review the options for more energy efficient equipment at what could be an opportune time.

Strategies and tools to improve real time control of energy use are also needed. Approaches to achieving this range from adopting very simple building energy design strategies with simple, intuitive occupant controls, through to buildings with highly complex energy management strategies implemented through building management systems with technically qualified building energy managers.

Aside from good maintenance, the season to season, day to day, hour to hour and minute to minute operation of a building presents the largest potential for maximising energy efficient operation or, conversely, of squandering energy through lack of information, understanding and ability to control.

Effective user-centric control of non-domestic buildings is perhaps the single largest failing in high-specification buildings, with services frequently found to be acting in conflict with one another, automated controls unable to reflect actual needs (e.g. for lighting), lack of clear occupant controls and high levels of energy use during unoccupied hours. The lessons being learned over and over again are to make building services as simple as practicable, with clear controls that occupants can use to modify their immediate environment. Where the strategy is for more automated control, for example where most users are transient or fabric and services are interdependent, it is essential to have appropriately qualified professional staff responsible for overseeing and adjusting the building controls, monitoring building performance and making the necessary modifications at appropriate timescales – operating a complex building is analogous to being a flight engineer or ship’s engineer. Many potentially excellent but complex buildings fail to perform as a result of this role being severely underestimated.

Where unskilled occupants do have control over aspects of their buildings’ operation, whether non-domestic or domestic, then simplicity, clarity and a modicum of education and engagement are recommended. The impact of what is often termed occupant behaviour on building energy use is an extensive research field. The way occupants use their homes, for example, can easily lead to 4 to 6 times energy use differences between almost identical buildings. Some of the impact arises justifiably from people living in their homes (after all that is what they are for), carrying out everyday tasks, heating their homes to a level they find comfortable and engaging in preferred pastimes. But some of the energy demand arises from ignorance and misunderstanding – not understanding how different systems work; how to turn them on or off; how to programme them, and the extent to which occupants’ actions can impact energy use. For many individuals there is little incentive for them to adopt more energy efficient practices as their energy costs, whilst increasing, are still well within their means and life presents other priorities.

The challenge is in part at least a marketing one – to engage the widest possible spectrum of society in acting to reduce energy demand in their homes and workplaces. Trigger points such as cost savings equivalent to sales volume for a retailer or the ability of tenants to afford their rent and hence not default for a social housing landlord could motivate different individuals and organisations. Linking these to information about current practices, guidance about changing practices and providing feedback on progress can reinforce and sustain impact. The introduction of smart meters and energy use monitors has the potential to provide real time energy use information, enabling feedback on actions such as switching off unused appliances. The psychological basis for relating this information to messages that connect with the motivations of individuals is very much work in progress.


Awareness of the significance of energy use in buildings is rising in both the domestic and non-domestic sectors and collective knowledge about how to minimise and manage the energy demands of new and existing buildings is growing rapidly.

The performance gap cat is now out of the bag so everyone is increasingly aware that they may not be getting what they thought they had paid for in new-build performance.

Better/simpler testing and verification methods are required in order for all stakeholders to check performance, close the loop and consolidate learning from practice. If these are made available and those delivering buildings can be held to account then greater emphasis on delivering promised/predicted performance will follow.

Energy efficient refurbishment of existing buildings is rapidly gaining recognition as a major challenge for the western world where the majority of buildings expected to be in operation in 2050, are already in existence. Here too, the performance gap must be minimised, with testing and verification before and after refurbishment becoming the norm. Rapid, robust, reliable, field-based methods are required.

Building owners, operators and occupants have a major impact on in-use performance and energy demand and providing real time energy use in intelligible, informative ways will give individuals the tools they need to understand and reduce their energy use and link this with individual and corporate motivation.

Improving the energy performance of our buildings will lead to a broad range of societal, quality of life benefits as well as addressing the global challenge of climate change and its impact on the urban environment.  To achieve this within available time scales, there is a pressing need for governments and all those involved in the sector to create the legislative, regulatory, and market conditions to accelerate the move to low energy, high-performing buildings.

This piece was originally published as the first chapter in the book Sustainable Cities: Assessing the Performance and Practice of Urban Environments, and is reproduced here with the kind permission of the book's publisher, I.B. Tauris.


  2. UNEP SBCI, United Nations Environment programme Buildings and Climate Change – Summary for decision makers, 2009.
  4. Energy positive buildings generate energy and hence contribute to energy supply. Carbon negative buildings remove CO2 from the atmosphere either directly through sequestering which is very unusual, or during operation by generating more energy from renewable sources than they consume. Buildings are often simultaneously energy positive and carbon negative but one does not imply the other.
  5. Reed R., Bilos A, Wilkinson S, Schulte K-W, International Comparison of Sustainable Rating Tools JOSRE v1, n1, 2009
  6. The Carbon Trust, Low Carbon Refurbishment of Buildings - A guide to achieving carbon savings from refurbishment of non-domestic buildings CTV038, June 2008
  7. Buildings Performance Institute Europe (BPIE), Europe’s Buildings under the microscope - Oct 2101, ISBN: 9789491143014, p.16
  8. Sustainable Energy Association, Clean energy measures in buildings are cheaper, Apr 14
  9. Energy intensity is the energy used per square metre of occupied floor space.
  11. Innovate UK, formerly The Technology Strategy Board, is the UK’s innovation agency tasked with using public funding to accelerate innovation across UK businesses -
  12. Final results are expected to be released by Innovate UK at the end of 2015
  15. The Standard Assessment Procedure (SAP) is the methodology used by the UK Government to assess and compare the energy and environmental performance of dwellings.
  16. Cooper E, Zheng X, Wood C, Gillot M, Tetlow M, Riffat S, De Simon L, Field trialling of a new airtightness tester in a range of UK homes, 36th AIVC conference, Madrid, Spain 2015