Inkling Blog #3: Closing the Building Performance Gap

Our last Blog identified a number of ‘Performance Gaps’ caused by a wide spectrum of conceptual and quality issues ranging from a lack of clarity in the industry regarding building performance criteria to poor build quality on site.

So, what can we do to close these gaps?

 
As engineers, modellers and designers we have the opportunity to address a number of the issues raised.
The lack of understanding of the purpose and differences between the various compliance and rating criteria is an unfortunate consequence of having different methodologies for DECs, EPCs and Part L, with the Part L targets changing every 3 years as the Building Regulations are updated. This is always going to be confusing and the only way to address this is by educating those within the industry so that they can explain in a clearer way to clients and design teams. Unfortunately this is tricky and unless the different rating methodologies are brought into line (which seems highly unlikely) it is a case of minimising the potential loss of credibility to the industry.

 
The publication of CIBSE TM54, Evaluating Operational Energy Performance of Buildings at the Design Stage (2013) goes a considerable way to addressing the gap caused by unsuitable or inaccurate prediction methods being used to predict building energy use at the design stage. It highlights the need to consider all energy uses within the building including the unregulated ones not considered by Part L. For example, lifts, catering and escalators can use considerable energy and are excluded by Part L for compliance purposes.

 
TM54 also explains that no matter how accurate the modelling, there will always be some differences between prediction and reality; in scientific terms this is ‘error’. Error, although used to mean ‘mistake’ in general language has a more precise mathematical meaning – it is not a bad thing, just a fact of life! Energy prediction results will always differ from reality and therefore TM54 suggests modelling a range of scenarios in order to show the range of results which are likely to occur in the actual building when built.

 
Finally TM54 provides a method of communicating the energy prediction results to the client and design team this has two important features. Firstly it highlights the inputs used in each scenario alongside the result and secondly assigns accountabilities for each input. For example, the efficiency of installed systems would be the responsibility of the designer and hours and pattern of use would be the responsibility of the occupier. These accountabilities are not always obvious.

More about TM54 here: http://www.cibse.org/knowledge/cibse-tm/tm54-evaluating-operational-energy-performance-of