Energy Efficiency Potential of Victorian Homes – AEF | Australian Energy Foundation

Energy Efficiency Potential of Victorian Homes

A study by the Australian Energy Foundation for Sustainability Victoria, May 2010.

AEF is undertaking a consulting contract with Sustainability Victoria. The research project is gathering information about the energy efficiency of existing Victorian houses. The study so far has given us a better understanding of just how inefficient Melbourne’s older houses are, what needs to be done to improve them, and how much it might cost.

Pilot project

As a first step, in 2009 Sustainability Victoria contracted AEF to undertake a pilot on-ground assessment project based on 15 existing houses. The houses chosen were typical of many of the homes in Melbourne’s inner north; built between 1900 and 1980, ranging from 75m 175 metres squared – much smaller than the average new home built today, and mainly free-standing weatherboard or brick-veneer.

Assessment process

The assessment of the houses consisted of the following steps:

  • Measure up of house to generate floor plan
  • Assessment of the thermal efficiency of the building envelope, which consisted of determining insulation levels in the house, orientation, building construction materials used, and how draught the house was
  • Survey of the installed lighting
  • Survey of the main fixed and non-fixed appliances (e.g. fridges, hot water systems, clothes washers, clothes dryers, dishwashers, heater, air conditioners)

Thermal modelling

The thermal modelling software ‘FirstRate5’was used to undertake modelling to determine how building shell upgrades (i.e. upgrades other than appliance or lighting upgrades) would impact upon the energy rating of the houses (energy rating is expressed as stars) – and also how much energy and greenhouse gas (GHG) they would save. The study also examined how much money, energy and GHG emissions could be saved by upgrading appliances and lighting to high efficiency models and technologies.


Blower Door Test

An innovative method, colloquially known as ‘a blower door test’, was used to determine how draughty the houses were. This test involves using a large fan to blow air up to 35km/h through the premises. The blower door test monitored how quickly air leaked through all the gaps and cracks in the house and is a comprehensive way to measure air leakage in a house. Often it is difficult to determine how leaky a house is as often the gaps and cracks are hidden and hard to find (e.g. behind cupboards, in the joins of buildings etc.).


The pilot project on the 15 houses provided an important information – that the average energy rating of the 15 houses was 1.3 stars – a long way below the Victorian Government’s target of upgrading all existing Victorian houses to a 5 Star equivalent standard by 2020.


That was the bad news. The good news was that the application of building shell upgrades – ceiling, floor and wall insulation, draught sealing, double glazing, drapes and pelmets, and external window blinds – significantly improved their rating. Two thirds achieved a rating of 4 stars or above, and one house achieved 5.3 stars.

Just as important was to find out which measures were the most effective. It found that 80 percent of the overall energy rating improvement from the building shell upgrades could be achieved just through wall, ceiling and floor insulation and comprehensive draught sealing. Significantly, these measures made up only 25 per cent of the total building shell upgrade cost, averaging – as a package – under $7,000 a house. Significant savings could also be made by upgrading hot water systems, heaters, air conditioners and other appliance to high efficiency models at the end of their operating life.

Follow-up study

AEF is currently assessing an additional 30 houses for as part of an expanded on-ground assessment project for Sustainability Victoria.

This is the rationale of the follow up study:

  • Sustainability Victoria wanted to expand the sample size from 15 so there was a more representative sample of houses in the study
  • We are studying a further 30 houses to expand the total sample size to 45
  • We are particularly focusing on houses from the 1980s and 1990s to ensure that the 45 homes sample size is more representative of the range of houses across Victoria
  • We are also looking at houses in Ballarat and Geelong to extend the sample beyond metropolitan Melbourne
  • This study will expand the evidence base that has been assembled for the first study and the results of this study will hopefully contribute to the further development of the 5 star equivalency Victorian Government policy
  • There are also a number of additional building shell upgrade measures that are being modeled for this project. These are reducing subfloor ventilation and also blocking up the wall cavity to cavity brick wall houses.

For the expanded project AEF is working with Air Barrier Technologies, Energy Makeovers, and RMIT University’s Centre for Design. We expect the final report for the expanded on-ground assessment project will be published in 2013. The data collected in this expanded study will be combined with data collected in the pilot study, to obtain a more comprehensive insight into the energy efficiency of the existing Victorian housing stock. The results of the research will be used to inform the design of more effective strategies and programs to help Victorians reduce their energy use, while making houses more comfortable and affordable to live in.