The “Performance Gap” – the difference between design predictions and operational energy use – is a serious issue for our industry. The CarbonBuzz web site shows that many buildings consume between 1.5 and 2.5 times the predicted design energy.

In order to address this, the industry needs both better energy-use predictions and a greater understanding of the variables involved in building energy use. With this in mind, in August 2013, CIBSE published TM54, which presents a methodology for evaluating building operational energy performance at the design stage. Better energy-use predictions require the full range of energy consuming activities to be considered. For example, energy use for lifts, security systems and servers must be considered alongside heating, cooling and fan energy.

Communication is key – TM54 presents ways to communicate the variability and uncertainty in building energy use predictions and to assign responsibilities for design and management decisions in order that possible savings can be targeted effectively. By considering low, medium and high scenarios when quantifying each energy use, a range of output results are produced which show the degree of uncertainty in the predicted operational energy.

The TM54 methodology is not just useful at the design stage – once built the predicted energy use can be compared to the metered building energy use in order to identify any discrepancies and ensure the building is functioning as designed and achieving the design energy targets.

Inkling are now pleased to offer predicted in-use energy modelling using the CIBSE TM54 methodology. Contact claire@inklingllp.com to find out how TM54 can benefit your projects.

 TM54 Scenarios for lighting showing key inputs and responsibilities

 TM54 Low-, Medium- and High-energy use scenarios