Traditionally, designers have presented Part L results as evidence of a building’s energy efficiency credentials – and, for the most part, this has been sufficient. Increasingly, however, clients and design teams are beginning to understand that Part L isn’t an accurate reflection of reality, and regulated energy is only half the story anyway.
There is a growing trend for construction clients to require designers to predict – and even influence – the total operational energy use of a building.
Total operational energy is made up of regulated components – including heating, cooling, hot water, fans, pumps and lighting – and unregulated ones, such as IT equipment, lab equipment, catering facilities, and so on. This means designers have to take some responsibility for unregulated energy use, which presents a challenge and, potentially, a risk.
As designers, our gut reaction may be to wash our hands of unregulated energy use. ‘We cannot influence user behaviour,’ we protest. ‘This is firmly outside our scope.’ This is true to some extent, but it misses the point of addressing what really matters to building occupiers and owners: the real-life energy use and running costs of their assets. This is the legacy with which they are left.
It makes sense, therefore, to discuss the intricacies of regulated and unregulated energy use with clients early in the design process. This includes tempering their expectations of the accuracy of operational energy prediction methods and discussing the influence of building occupant behaviour.
The drivers for predicting total operational energy
It goes without saying that building owners will be concerned with minimising the running costs associated with their assets. Increasingly, however, organisations are also faced with carbon emissions targets, whether internally or externally imposed. In some cases, this has led to caps being put on the allowable carbon emissions from new buildings. By addressing total operational energy more effectively, we can:
- Gain a better understanding of future energy use and, so, carbon emissions
- Understand how buildings are expected to perform, so control alterations and behaviour-change initiatives can be targeted effectively
- Build better quality buildings that assist users with energy efficient operation.
Regulated energy uses are inherent in the design of a building; they are related to the ‘quality’ of the building itself. While designers cannot predict how these things will, ultimately, be used, they can ensure they are installed to be as energy efficient as possible.
Unregulated energy uses, on the other hand, are often undetermined until very late on in the design process. They will also vary significantly throughout the life of a building, as spaces are used for different purposes. In some building types, unregulated energy can account for around 50% of total energy use.
It is true to say that designers have very little influence over which unregulated energy uses are included and how they are used. So it is unreasonable and impractical to demand that they are ‘responsible’ for total operational energy. Designers can, however, work with their clients to attempt to predict total operational energy, and empower them to minimise it through the inherent building design and the way occupants use it.
In some building types, unregulated energy can account for around 50% of total energy use
Can designers really influence unregulated energy?
Undoubtedly, facilities managers and building occupants have the biggest influence over unregulated energy, but the way a building is designed can enable or hinder the occupants in using equipment efficiently.
Strategies to minimise unregulated energy use that we have employed in recent projects include:
- Locating shared facilities – such as freezer farms or autoclaves in laboratories – centrally, to discourage the inefficient use of smaller, individual pieces of equipment
- Master shut-off switches and easily accessible sockets, to encourage users to switch off equipment when it is not in use
- Dedicated chemical storage areas in labs, to discourage users from using fume cupboards as storage
- Energy monitor display screens, to raise awareness of energy use and influence user behaviour
- Integrated infrastructure for ‘green’ IT
- Post-occupancy evaluation and adjustments.
Calculating operational energy
The best methodology we currently have for calculating operational energy is set out in Technical Memorandum 54 (TM54), published by CIBSE in 2013. TM54 offers guidance on how to make more accurate energy estimates based on the intended use and operation of the building.
Case studies have shown that TM54 can predict operational energy of a building to within 15%.1 In the two and a half years since its publication, however, uptake of the methodology is, anecdotally, low. One possible reason for this is the additional cost to clients. I have seen fees of up to £30,000 to undertake a TM54 for a large building.
A sensible approach for designers is to discuss the benefits and limitations of a TM54 analysis at the outset of a project. This could include an estimate of the associated cost and the payback on their investment.
The rebound effect
At this point, it is worth mentioning a further complication to the business of predicting operational energy use – a phenomenon known as the rebound effect.
This describes a situation where savings from energy efficiency may be cancelled out by an associated increase in energy intensive behaviour. Are you less inclined to switch off your new energy saving lightbulbs, for example? Are many energy efficiency measures a case of two steps forward, one step back?
Research into this phenomenon is in its infancy, and it isn’t something we would attempt to account for in our operational energy calculations. However, this highlights the need to invest time in educating our clients to understand the many complexities of how occupant behaviour affects the energy use of their building, and what they can do to minimise it.
Savvy clients are increasingly aware of the importance of understanding the total operational energy use of their buildings.
For designers, there are many complexities and risks involved in predicting total operational energy – in particular, the unregulated element. However, it is our duty to assist and educate our clients.
It makes sense to start discussing operational energy, including the unregulated component, with our clients from the outset of a project. We should also be mindful of how our designs can enable or hinder building occupants in using equipment efficiently.
- Case studies have been carried out by CIBSE and, more recently, by British Land. Primarily, they have been done on office buildings; more complex buildings – such as research and technology buildings – would be much harder to predict, however.
Kate Dougherty is principal engineer at WSP.