Energy efficient homes

Research by the VBA into the characteristics of typical home renovations in metropolitan Melbourne found that this work predominantly involves two building styles:

  • Post war (original construction in 1945 – 1965)
  • Californian bungalow (original construction in 1920s)

In order to assist building professionals design and renovate existing houses in a way that best improves building performance, liveability, thermal comfort, energy efficiency and reduces utility costs,  the VBA has created three guidance sheets.

The guidance sheets take the form of renovation case studies that generally reflect market renovation trends, objectives and budget constraints and provide information on careful planning and design before embarking on a major home renovation project, in particular that:

  • high performing energy efficient design with a significantly better Star Rating can be delivered within the typical home renovation project budget
  • improved energy efficiency will contribute to lower fuel bills, enhanced comfort and liveability, not to mention potentially higher resale value when it's time to move
  • the building designer focuses attention on insulation levels; window detailing, sizing and location; internal zoning, location of living areas; effective sealing and weather-stripping
  • water efficiency improvements are simple to incorporate into the renovation design with an increasingly wide range of suitable products available.

The three renovation case studies were rated for their overall energy performance using the Accurate energy rating software in accordance with the national house energy rating scheme (NatHERS) as per the requirements of the National Construction Code.  All three renovated case studies rated above 7 stars which is significant as the average House Energy Rating (HER) for houses constructed in Victoria before 2005 was 1.81stars

Case studies

Existing star rating

Renovated star rating 

House 1 – Post War (1945 – 1965)

2 stars

7.4 stars

House 2 – Post War (1945 – 1965)

2 stars

7.7 stars

House 3 – Californian Bungalow (1920s)

2 stars

7.4 stars

Renovation energy rating assumptions:

  • The rating has been undertaken with the assumptions noted on the plans published here; the wall types shown; the recommended insulation levels; and the recommended windows.
  • Venting to subfloor walls is the minimum 6000mm2/m as per the NCC
  • There are no downlights
  • All exhaust fans duct externally with self-closing mechanism when not in use.
  • External doors and windows are all weatherstripped
  • Existing windows have been replaced with new
  • Neighbouring homes are the same size and same setback as the rated house
  • Any cavity connecting the wall, the subfloor, and the attic is sealed to stop unwanted mixing & heat loss
  • Occupant behaviour: as per the Rating Protocol assumptions, occupants will endeavour to maintain desired temperatures through the operation of windows, blinds, and ceiling fans. If such measures are inadequate then mechanical heating or cooling will be invoked.
  • Ratings based on Accurate calculate engine V1.1.4.1

Please note: The guidance sheets are provided to prompt consumers to consider design and layout options that will provide an enhanced indoor quality and energy efficiency rating.  They are not intended as construction documents and the VBA does not endorse any house design.

If you require further information about sustainability and home renovations, please refer to the below links: