CIBSE TM54 Evaluating Operational Energy Performance of Buildings at the Design Stage

This guidance will help to turn low energy designs into low energy buildings that achieve the design energy targets.

As energy costs have risen, there is an awareness among building owners, who hear much about low energy buildings and subscribe to programmes that rate the design of the building, that their ‘low energy design’ turns out to be have a typical energy bill. The performance of low energy designs is often little better, and sometimes worse, than that of an older building they have replaced, or supplemented.

There are two main reasons for this performance gap. This guide addresses the first, which is that the method of calculating energy use for the purposes of compliance does not take into account all the energy uses in a building. In particular, it does not address energy used by lifts and escalators, for catering facilities, or for server rooms. This energy use can be substantial.

This Technical Memorandum (TM) provides building designers and owners with clear guidance on how to evaluate operational energy use more fully, and accurately, at the design stage.

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Friday, 4th October 2013

Colin Lillicrap, Colin Lillicrap Associates

I endorse all that Phil Jones has said above. While many of us have been using similar methodologies for many year we now have a document that lays down a step by step process to predict the operational energy use in a building including all end uses.

The document will be useful as basis for working with designers and developers, educating them about what can be achieved with modern dynamic simulation software and the uncertainties that will always be present in the input data and hence the predicted operational energy use. The proposed method for presenting results so that assumptions are transparent and the high and low forecast is excellent.

Unfortunately our fragmented construction industry rarely seeks detailed design analysis based on simulation software. In my experience most developers specify only the minimum required by the Building Regulations and are only prepared to pay for an SBEM calculation and BRUKL report.

I can only reiterate what Phil has said, we need clients to ask their designers to produce estimates based on TM54.

Colin Lillicrap
Low Energy Consultant

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Wednesday, 2nd October 2013

Phil Jones, Building Energy Solutions

TM54 is a really excellent and important publication and a big step forward for the energy performance sector. It's not just guidance, it provides a step-by step methodology for designers to follow that brings consistency to estimation. It also has lots of helpful numbers on inputs to the method, giving support designers.

Also really important are the ideas about presenting the results to clients to help them really understand true performance and avoid the performance muddle we have got ourselves into.

What we need now are ways to encourage designers to use the methodology but even more importantly ways to get clients to ask for their designers to produce estimates based on TM54.

Phil Jones
Independent Energy Consultant & Chairman of the CIBSE Energy Performance Group

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Opinion

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