What is the best way to provide an energy rating for an extension to an existing dwelling?

  • DTS Extension,
  • FirstRate5
  • Victoria
Last Updated: February 20, 2020


I have been asked to provide an energy rating for an extension to an existing dwelling. They are proposing to add another two bedrooms plus a rumpus room. The extension is 68m2 in size which equates to approximately 37 % of the existing building.

Can you please guide me on the best way to approach this assessment?

Do you have a template or information on what I need to provide for an elemental deemed to satisfy report? May I have some guidance on how to complete a deemed to satisfy report?


The response will depend on the level of interest the client has in knowing the detailed thermal performance of the house.

If simple regulatory compliance is the desired outcome, then an elemental Deemed to Satisfy report will be quick and cost effective.

If a NatHERS DtS approach is required to actually quantify the energy demand profile, then before and after ratings employing the VBA Practice Note 55 adjustment formula to determine the required star rating will deliver a suitable result.

Design Matters has available to members in the TPA Practice Notes section a Sample DtS Report, TPA 008-2015.

It is important that anyone using the form has developed an understanding of the benchmarks in place for Elemental DtS compliance thresholds.