Why? When? How?
Dr. Kerry Mashford, Chief Executive of The United Kingdom’s National Energy Foundation (NEF), which has been at the forefront of improving energy use in buildings since 1990, argues evaluating a building’s energy performance is an essential component of smart energy management.
Faced with the urgent and important demands that facilities managers are presented with every day, it’s understandable that the equally important but less immediate challenge of optimising energy efficiency often has to take a back seat. It’s often difficult, messy and complex to understand how much energy your building is using, and how to break energy down into end-uses, time periods, zones and even tenants. Then there’s the question of differentiating the building’s intrinsic energy use from that needed to run its operations and activities. All told, it isn’t surprising that, in spite of the rhetoric surrounding the energy performance of buildings, relatively little is done in practice.
WHY AND WHEN TO EVALUATE?
There are many reasons for evaluating the energy performance of your building. However, regardless of whether you’re taking over ownership or tenancy; and even of whether a building is newly built, refurbished or established, you should never rely solely on theoretical performance assessments.
Compliance certificates - for example, Energy Performance Certificates (EPCs) and Building Regulations UK Part L (BRUKL) Certificates in the United Kingdom, are issued on the assumption that any building as built will mirror the as designed performance characteristics of its fabric and services. And although these are theoretically the same, in practice they aren’t.
Recent global studies (including those published under the United Kingdom’s Technology Strategy Board’s Building Performance Evaluation Programme) have found that, on average, non-domestic buildings use two-and-a-half times more energy than predicted.
This performance gap arises from a combination of factors but evaluating the energy performance of your building as part of the hand-over process will enable you to ensure the fabric is up to scratch; and that services are installed and commissioned properly. The flip side of this is if you’re responsible for marketing a property, potential tenants and purchasers are going to be interested increasingly in as built performance figures.
With buildings that you already own or occupy, evaluating energy performance equips you to manage energy use better on a daily basis, and to identify and prioritise opportunities for energy-related improvements.
And although there are different motives for undertaking evaluations; including capital investment, education and building management modifications, it is certain areas for energy saving will be identified: one well-known United Kingdom property owner found it was able to save 20 per cent on landlord energy use through basic, low-tech measures, and to negotiate better energy tariffs by adjusting demand dynamically after smart, real-time monitoring of energy use patterns in its buildings.
Comparing the energy performance of buildings in your portfolio and comparing individual buildings to others of a similar design or category, gives a real sense of how big opportunities for improvement can be and enables you to focus clearly on the low-hanging fruit of energy inefficiency.
A number of web-based tools are available (some for free) including Carbon Buzz and Energy Deck. Carbon Buzz, compares the “energy intensity” (annual energy use per square metre) of any given building against CIBSE TM46 sector benchmarks and data from other buildings that can be filtered to include those which are similar to yours.
Even if you don’t compare energy use in your own building or buildings with others, tracking energy use over time enables future targets for reduction to be set and underpins investment decisions. For example, if service equipment becomes inefficient as it ages, monitoring energy use can alert you to equipment failures, unauthorised reprogramming of controls or changes in occupancy; and enable you to respond quickly to building occupant needs without wasting energy.
The final reason for evaluating energy performance in buildings is to protect the value of property assets and avoid any potential threat of regulatory obsolescence if performance fails to meet standards that may be required at the time of any future transfer of ownership or tenancy.
HOW TO EVALUATE?
The old adage: “if you don’t measure it, you can’t manage it” applies. But what should you measure? How? How often? And how should you interpret any data?
Energy performance evaluation is a significant subset of overall building performance evaluation and, I would argue, provides valuable additional insight into why energy is used; in addition to where and when.
For in-use buildings, best practice is to carry out periodic studies (for example, during the summer and also in the winter).
Changes of circumstance; for example, in the use of a building or as a result of the replacement of key equipment, will also trigger a requirement for a new study.
All evaluations should draw on data captured over the whole year; and typically, half-hourly meter data, internal and external temperature records and services operating records.
Using a spreadsheet-based tool such as CIBSE TM22, you can capture and document the energy used by occupants and, by combining it with an occupancy profile, predict the building’s expected energy uses.
If your building has a good, reconciled sub-meter arrangement, you can record measured and disaggregated energy use which will help to identify and quantify discrepancies and identify any new opportunities for energy savings. In order to use the TM22 and similar spreadsheets, you’ll need data from sensors, thermostats and meters. However, even if your building is minimally monitored, has no building management system (BMS) or only a main electricity/gas meter or simple, programmable timer for HVAC systems, space and water heating, you can still use this information in combination with an estimate (or actual count) of hours used by energy-using services and equipment (including lights and computers) to get a pretty good estimate of where, when and how energy is being used in your building.
If this is starting to sound a bit complex, think of the savings you’re almost guaranteed to make.
It’s also reassuring to know that specialist help is available through numerous consultancies and (in the United Kingdom) charities such as the National Energy Foundation. Many organisations will even offer advice without up-front costs in exchange for a share of any financial savings made.
There are two other key aspects to building performance evaluation that contribute significantly to energy performance evaluation: site inspection and occupant surveys.
Site inspection is about taking a good look (and listen) at your building; from top to toe, inside to outside and boardroom to plant room.
Look at the fabric of the building; look for hot spots in summer and cold spots in winter. Also look out for draughts, doors that don’t quite close, cracked or broken windows, and gaps around services penetrations or where modifications have been made.
Look at services themselves, and especially HVAC systems; and check for lagging of pipes, excessive fan noise or programming that doesn’t fit occupancy patterns.
Consider the settings and controls in the building. Are offices and meeting rooms too hot or cold? Do they have both heating and air-conditioning (potentially fighting each other)? Do factory floors and loading bays have large doors that stay open for longer than necessary? What about compressed air leakage? Is internal or external lighting left on overnight? How do cleaning staff leave the building? Is office equipment left on when not in use?
Ideally, carry out one site inspection during occupied hours and another when the building is not being used. Ask yourself: how much energy is my building using when I’m not using it?
Because the vast proportion of this energy is simply wasted, it can be a quick “win”; offering potential savings without impacting on any of the building’s normal activities.
The final component of building performance evaluation (and one that is not to be underrated) is the perspective of occupants.
A structured survey method such as the Building Use Survey (BUS) which has been honed for more than 30 years following research in the United Kingdom into non-domestic post-occupancy building evaluations and includes a large database of properties already surveyed, provides maximum benefit to the surveyor as well as benchmarking against other buildings in terms of a range of comfort factors.
Alternatively, occupant feedback can be captured using a home grown survey at very low cost and, most importantly, individual and collective survey data can be cross-referenced with other information from site surveys and energy monitoring to identify wasted energy.
Consider, the example of glare on computer screens which often results in occupants of offices drawing window blinds and using additional artificial lighting during daylight hours. A simple change of the office layout can address the root cause of the problem and thereby reduce energy consumption whilst also improving the working environment.
Energy performance evaluation will increasingly be an essential responsibility of Facilities Managers and will benefit all building stakeholders; from shareholders to employees and customers.
And whilst you’re likely to need external expertise when evaluating complex buildings, it is possible with only a little help, training and support to undertake basic evaluations of building energy performance. Ultimately, all that’s really required is a common sense approach, good observational skills and a willingness to act on any findings!