First of all, if you’re not sure what TEUI3 is, Take me to the Index of Articles!
Architects imagine buildings in great detail before they exist. They establish budgets for construction costs, and their contracts will often hold them to delivering projects within a certain percentage of these targets. The buildings are expected to perform in many ways, such as to not blow over in a stiff wind, to not fall down, to provide safe exiting in case of fire, or to suppress fire if it breaks out. The building codes set many of these structural and life safety aspects for designers to comply with, and so too are thermal characteristics established by the codes. In fact, much of what architect do can be thought of in terms of reviewing and setting targets, and then finding ways to meet these targets with the building design. TEUI3 is a tool (currently an excel spreadsheet) that assists designers to establish Targets for Energy Use and Carbon Emissions. But here’s the thing with a Target – you don’t always hit a bullseye – but that is nevertheless what you are aiming for.
In a way, a Target represents your best professional guess at how a building will perform, and the skill and experience of the Architect is often the determining factor in hitting these targets. The more practice one accumulates in using any tool, and the more buildings a practitioner has benchmarked, the more likely it is that established targets will be reached. The purpose of this post is to address concerns users of the tool rightly have about making any claim of meeting a target before a building is constructed. The proof of having met a performance target can only be verified after at least one year’s worth of energy bills can be reviewed and entered into the tool. That is why there are two sections, and two modes for data entry in TEUI3, ‘Target‘ and ‘Actual‘. In all Design stages, TEUI3 should be set in Target mode at the toggle called S.2 Actual (Bills) or Targeted (Design) Use (see image below). Targets can be thought of as a fiction, a story that we tell about a building that we work to make come true. However, just as with any plan of action, life often gets in the way.
But, Mousie, thou art no thy lane,
In proving foresight may be vain;
The best-laid schemes o’ mice an’ men
Gang aft agley,
An’lea’e us nought but grief an’ pain,
For promis’d joy!~ Robert Burns
When this happens projects may breach budgets, extras may need to be considered, revisions are necessary and contractual obligations may be challenged by both parties. Architects obviously prefer to limit these risks, and so use of this tool, like any other tool the Architect uses, must be used with great care, and careful communication with the owner/client about its use should elucidate the difference that establishing a Target, is in no way creating an Estimate or Prediction of future performance, the Targets are simply the numbers we are aiming for.
Architects cannot guarantee performance whether this is strict compliance with a budget or in reaching energy or carbon targets, but they can aim for reaching a performance target, the language around costing budgets is similar to what we should use around energy budgets. This is related to the concept of a ‘Duty of Care‘ in our profession – which can be summarized as a professional using a reasonable level of skill and expertise in exercising their design responsibilities. This is very different than a ‘Standard Of Perfection‘ which is expected in aviation and automotive industries, where getting astronauts to a space station will have numerous redundancies and a level of precision and de-risking that is of a completely different order of magnitude from construction. Until a design team or Architect is sufficiently confident in the use of any this, or any design tool, it may be wise to use this tool only as a backwards-looking performance verification tool when targets are actually met. The more experience the designer gains in the use of the tool, the more it can be used at all phases of design, but one should start by evaluating projects where post-occupancy energy data is available, to determine benchmark levels for all of the noted metrics, which will assist the designers to understand what setting reasonable targets can look like.
Now many readers that are unfamiliar with Energy Modelling will have reached this point and concluded that setting these kinds of targets is fraught, and it is likely better, and safer, to not even bother. However, as with any enterprise, when we do not even try, we are most likely to fail.
However Energy Modelling professionals are well-used to these kinds of disclaimers in both standards and softwares and as just one example here is an informative note from ASHRAE 90.1 that speaks to the issue:
“actual experience will differ from these calculations due to variations such as occupancy, building operation and maintenance, weather, energy use not covered by this standard, changes in energy rates between design of the building and occupancy, and precision of the calculation tool” (ASHRAE Standard 90.1-2013, 11.2 Informative Note)
There is an incredibly broad range of factors that influence the difference between Targeted Energy and Carbon use and Actual values. Weather variability from year to year can alter results as much as 30% (ie. an Extreme Cold or Extreme Hot year). User behaviour can also have a profound influence such as when occupants leave windows open in the prime heating season, possibly misunderstanding that mechanical systems are delivering a supply of fresh air at all times. Plug loads and Lighting loads may be higher than expected, again, related to user behaviour, or a building may have been insufficiently commissioned to arrive at optimal operating conditions for the mechanical systems. The designer often has zero control over these influences, and these, among hundreds of other reasons are why we set Targets grounded in the requirements of the building codes and other standards, and why we explicitly do not make Predictions.
If we already have Engineers and Energy Modelling professionals on our design team, why should we bother to use this tool at all? The simple answer is the greatest opportunity to influence the design and energy performance, at the least cost to the project, is in the earliest phases of design. Where we show the red dot in the image below, is the phase at which the TEUI3 tool is intended to be used, well before the coordination with Engineers and Energy Modellers typically happens – in the coordination and/or Design Development phases when many key aspects of the design have been locked up. By establishing performance targets early-on, the quality of the integration of the engineering and design teams can be accelerated and enhanced, with better conversations around systems and strategies, massing, thermal envelope, glazing, ventilation and occupancy considerations. The performance and carbon targets can be hashed out and optimized, adding incredible value to the project for both the design team, stakeholders and ultimately the public. With TEUI3, the goal has always been to restore some capacity to Architects to influence thermal and environmental design, since overall building geometry, construction assemblies, and programming/occupancy considerations has always been a core part of our practice, TEUI3 can help us understand how we can optimize these aspects of our design skills.
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