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Over the years the green agenda within building design has become increasingly important. It’s only until very recently that designers, and other construction colleagues, have had the technology and know how to validate how our buildings are performing in real terms in comparison to what was expected from the design stage. The results prove interesting with a common thread, often the building isn’t performing as predicted. Invariably the divergence in results show the real building performing far worse than expected. We can see this in simple terms, by comparing a buildings Energy Performance Certificate (EPC) against its energy bills and Display Energy Certificate (DEC). Why is this?
IES’ recent Faculty held on the 24th September at the Institute of Medical Sciences discussed where the Performance Gap comes from and how the industry can minimise it through better understanding of design analysis and learning from buildings in operation. This Faculty is one of many from the Faculty series, which is a free event for IES Virtual Environment (IESVE) users to discuss and debate current topics among like-minded people. IES’ new Cloud Services brings together Design and Operation through its new FFD technology.
Simulation modelling for building performance actually comprises of a number of different models, these model types are:
1. Compliance Model = Actual Building
2. Reference Model = Notional Building
3. Design Model = Best estimate of the REAL building
4. Operational Model = refined Design Model with REAL Building in operation data, usually a heavily manual process
The VE allows you to analyse each of these models within a single software suite for your project, however this can lead to confusion. The Carbon Trust published a report, ‘Closing the Gap’, in April 2012. One of the key findings is the confusion that Compliance models should somehow suffice for design analysis and in some cases mistakenly used as a form of operational energy prediction. The compliance model is simply a benchmark exercise and omits key elements within the building in its calculation. For example, unregulated loads such as plug loads, server rooms, external lighting and so on. This is ultimately why the EPC, currently, won’t align with the DEC, however your Design model could, and a growing number within our industry would say should. The Carbon Trust report further concludes that during the Design process we should distinguish between these model types and focus on the Design model rather than being driven by compliance. In addition the report concludes that we should also develop our understanding of soft landings and post occupancy building monitoring, and increase their application to benefit our Design decisions through lessons learnt.
There is an increase in clarity of these different model types, helped by the sophistication of BIM Analysis for building performance software suites such as the VE. In addition to the technology has been the need to introduce standard methodology to assist designers. CIBSE TM:54 outlines a methodology for developing the compliance model to evolve to a detailed Design model. This comprehensive technical memorandum, helps to reinforce how many of us already tackle projects and it’s a positive step forward to have an independent body produce a standard process for doing so. Everything you need to follow this methodology can be achieved within the VE.
We carried out a poll at the Faculty to understand the impact of TM:54 almost a year after publication. It’s interesting that approximately 5% attendees had actually used it, 10% had read it, and around 50% had heard about it. Why is this? TM:54 was published October 2013, maybe we need more time for the TM to distribute, or maybe its market demand. It seems to us that this should be standard practice on every project, but we are maybe a few years away at the moment. One response at the faculty pointed the finger to client demand. Saying that the client won’t pay for a more advanced model, and so they get a compliance model. Indeed one of the commercial editors of TM:54 later confided that their business has yet to deliver a project following the methodology and struggling to sell as a service. Maybe though we should have more confidence, and as the experts, help to educate our clients on the benefits.
Understanding our analysis at Design Stage is only one half of this challenge, the other is understanding how buildings are operating and learning from them. Historically we’ve periodically undertaken volume benchmarking of buildings, i.e. CIBSE Guide F (table 20.1 is one I personally remember well, from design days of past). This approach requires a huge amount of effort and quickly becomes dated. We have had recent attempts to create independent formats for example ‘Lessons’ and ‘CarbonBuzz’. While these appear to be robust platforms with good intentions, designers & building owners are reluctant to post predicted and operational building performance key indicators on a public forum. The feedback from the Faculty suggested the lack of a driver. Why would designers commit to their design performance so publicly?
Interestingly the BREEAM assessment Version 2014 includes the reward of credits for submitting building performance metrics. However there seemed to be a difference of opinion at the faculty on this, with some hesitant to share any information, whilst others happy to comply for credit attainment. There is a need to learn more from our buildings in operation. It’s all well and good believing a building is sustainable because it appears to do so at design, but how sustainable is it in reality? How do we know if we aren’t checking? It’s well-known that there are some new high profile sustainable buildings which perform far worse than expected, TM:54 gives the example of the National Trust HQ in Swindon. Soft Landings is keys to this, but we need to correlate building performance against the design. We need to quantify the Performance Gap in the same level of detail which we analyse buildings in simulation software. IES has been working hard to provide a robust technology platform to do this, and announced at the faculty its new Cloud service called ERGON, which allows operational data to be used within the VE, through Free Form Data profiles (FFD).
ERGON, certainly got the discussion going at the Faculty. Being able to use real building data at design stage is a leap forward. Imagine not having to rely on NCM profiles, but actually using real building data. ERGON is essentially the introduction of a new fifth model category, the Enhanced Operational Model. Where previously the Operational model would involve site visits and laborious data analysis, the Enhanced Operational Model automates much of this and allows a much more efficient and effective workflow. Take the example of designers who are sector specialists. If you have data of how the schools you have designed perform, you can directly use that to benefit the design modelling of your future school projects by using more accurate and relevant data. The Faculty presented a couple of ERGON case studies of real metered data against predicted (using compliance data), with one case study showing the metred lighting load at 200% of predicted.
No-one knows better than the designers who design the building, how that building should operate. We currently have very poor handovers from the design team, to the construction team, and as one Faculty attendee shouted out, don’t forget the handover to the FM team. Using the new FFD service designers now have the ability to extend their services beyond the traditional handover. Using the same technology they are used to for design, they can now feedback valuable information to the commissioning team and FM team. As pointed out in the Faculty, a service contact with building owners to provide annual health checks, could be another opportunity.
While the Faculty discussed some of the new features of the VE, there’s much more to come. It’s a very interesting and exciting time we live in with the advancement of smart building technology evolving at speed. Only a couple of years ago the only thing connected to your home broadband was your laptop. Now with the movement of the Internet of everything (IoE), all manner of devices are connected. It’s easy to question the value of having your fridge or washing machine connected to the internet, but the popularity of being able to control and analyse your home technology from your smart phone is hard to argue with. Just look at NEST’s smarts smoke alarm and their smart thermostat. Ok, it’s great to turn your heating on or off from the office and to check your house isn’t on fire but the real benefit comes from a sub benefit of the products being connected to the IoE. i.e. if the smoke alarm senses Carbon Monoxide it can tell the thermostat to turn the boiler off.
The evolution within the domestic sector is clear but what about the potential of the non-domestic sector? It’s an exciting time and with all the development being carried out in various Smart cities projects around the world, were only at the beginning. It’s hard not to be distracted by this; but our first step to this must be to close the Performance Gap.
Find out more about ERGON by signing up to our free training webinar on Monday 10th Nov (3pm GMT).
There has been a growing awareness for some time that many ‘low energy buildings’ use more energy than the designers thought they would. As energy costs have risen, this awareness has started to spread to building owners, who hear much about low energy buildings and subscribe to programmes that rate the design of the building, only to find that their ‘low energy design’ turns out to have a typical energy bill. The performance of low energy designs is often little better than that of an older building they have replaced, or supplemented.
There is a mismatch between the expectations around the performance of new buildings and the reality of the utility bills. This difference between expected and realised energy performance has come to be known as the ‘performance gap’. CIBSE TM:54
Join the IES Team in London on Wednesday 24th September (4pm – 6pm), for the return of the next instalment of our popular interactive Faculty series, where we explore the Performance Gap phenomenon in detail. We’ll discuss what we can do to improve the accuracy of our design modelling, with an insight into the newly released CIBSE TM:54. Following on we’ll discuss the advantages of Soft Landings and what recent advances in Building Simulation can allow you to use real building data to improve the Design Process of new buildings.
Can’t make the seminar in person? Don’t worry, we’ll be providing live updates throughout the event on our live twitter feed, using the #PerformanceGap hashtag. Not only can you follow our World Green Building Week event live but you can also play your part in the discussion taking place, by filling out this quick survey below and by putting your questions and issues to our team using the #PerformanceGap hashtag or the comments section of this blog post.
The Faculty seminars are a place for interaction among the industry and the more feedback that is provided, the better we can start to address the issues we are all facing. It’s time for us to close the #PerformanceGap.