KJ Tait

Design for Performance

Our modellers are skilled in using the IES programme Apache HVAC so we can offer the Design for Performance framework for all office projects. The framework ensures that the energy demand of new and refurbished buildings is as low as possible and is a robust methodology for estimating the in-use performance of a building and NABERS Star Rating when no actual energy information is available.

We lead the sustainability agenda through the early stages of a project and look for enhanced energy efficiency measures such as improved fabric and thermal bridging along with better controls of the HVAC systems. At the conclusion of Stage 4, we produce a Simulation Report detailing the likely NABERS Rating the building could achieve in-use and a Rating Achievement Plan as to how, together with the Client, we intend to achieve it. This could be through aspects such as Soft Landings, in-use energy monitoring and regular reviews of the BMS.

We then instruct an Independent Design Reviewer to validate the design, modelling and sign off the NABERS Target Rating which allows our Clients to market their building.

In order to address the ‘Performance Gap’ between a designed building and the operational performance once in-use, we are skilled in designing and modelling Design for Performance standard buildings. The process ensures that energy demand is reduced as far as possible via a collaboration process between the Mechanical Engineer, Electrical Engineer, Architect and Thermal Modeller.

The Design for Performance process involves the use of software that is capable of detailed definition, configuration, control and modelling of HVAC systems. At KJ Tait we use the IES VE programme Apache HVAC to model all our buildings that go through the framework.

The resultant energy consumption from the modelling is translated into a NABERS Target Star Rating out of 6 stars and the report and design documents are sent to an Independent Design Reviewer to assess both the design and the thermal modelling. This ensures that the process is as robust as possible for determining what the NABERS Target Star Rating would be.

After one year of at least 75% occupancy, the NABERS UK In-Use assessment is carried out to ascertain the Actual Rating of the building using the actual billing and metering information. If there are any discrepancies between the Target Rating and the Actual Rating, the Assessor will provide operational recommendations to bridge the performance gap.

There are many advantages for office buildings to go through the Design for Performance framework including:

  • Increased likelihood of achieving Net Zero carbon development by bridging the performance gap between design intent and operations
  • Attracting blue chip and/or anchor Tenants
  • Reduced capital costs by specifying more appropriately sized plant and equipment
  • Increased likelihood of achieving desired building quality and operational performance
  • Marketing and communications opportunities.


KJ Tait is currently working to the NABERS Design for Performance framework for a refurbishment and new build project in Edinburgh city centre. Constructed in 1898, 28 St Andrew Square is a Category A listed building within the Edinburgh World Heritage Site Boundary.
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We have recently submitted our first Design for Performance (DFP) to the Independent Design Reviewer.
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