Policy and industry lessons from my own retrofit 16 June 2021


By Rob Murray-Leach

Over 7 million Australia homes were built before energy efficiency standards were introduced into the National Construction Code. Many of these homes are draughty and have insufficient insulation, especially in the walls. These ‘permanent tents’ are freezing in winter, baking in summer and cost a small fortune in energy to run.

I know – I live in one.

According to the ABS my house is painfully average for a house built in Australia before 2000:

  • Wooden framed, like 64 per cent of homes surveyed in 2000;
  • Tiled roof, like 63 per cent; and
  • Brick veneer, like 41 per cent.

On the energy efficiency front, it’s even more painfully average for a house built before energy efficiency standards came in. My house has:

  • Some ceiling insulation, but its far less than ideal;
  • No insulation in the walls, like 86 per cent of homes surveyed in 1999;
  • No insulation underfloor, like 99 per cent of homes surveyed in 1999;
  • Single glazing, like 98 per cent of homes surveyed in 1999; 

One area where my house was unusual is that it has incredibly inefficient plug-in electric panel heaters. Most Victorian houses either have gas heaters or efficient reverse-cycle air conditioners.

All-in-all, my house is a bit of a dog, but that makes it a fantastic case-study for retrofitting.

Why retrofit homes?

Retrofitting older homes will reduce energy bills and greenhouse gas emissions but this is really a side-benefit. The main driver for retrofitting older homes is the health and wellbeing of Australians. One study on the benefits of upgrading New Zealand homes found that health benefits accounted for 99 per cent of the benefits, dwarfing the energy savings. Another study estimated that improving the average performance Melbourne’s homes from 1.8 stars NatHERS to 5.4 stars would reduce deaths in heatwaves by 90 per cent.

Retrofitting homes will also create a huge number of jobs. In 2020, the International Energy Agency recommended that retrofitting homes should be a key part of economic stimulus, as it is the most ‘jobs-rich’ part of the energy sector. In Australia, Green Energy Markets has estimated that carrying out basic upgrades on existing homes would create 34,000 job-years of employment, and that is a very conservative estimate that doesn’t include jobs in energy efficiency rating, design work, draught-proofing, glazing, and wall and underfloor insulation.

The health, energy, climate, and employment benefits that come from retrofitting homes mean that Australian associations for welfare, health, tenants and construction are increasingly pushing for a national retrofit strategy. These associations have been inspired by efforts overseas, particularly the ‘renovation wave’ in Europe that aims to retrofit all homes to a decent standard by 2050.

Retrofitting my home

This big-picture theory is fascinating, but I’ve got to be honest - the main reason that I’m retrofitting my house is that it was absolutely miserable last winter. My heating bill was massive, but the house was still freezing, typically below 10 degrees when I sat down at my desk. Even worse, the aluminium window frames often had mould patches on them because they were so cold they’d act as condensation points. The World Health Organisation advises that indoor temperatures below 18 degrees can create health risks for occupants, and so can mould. So, all in all, far from ideal!

Figure 1: My electricity and gas bills (two occupants)                                       Figure 2 Miserable temperatures and mould


Note: The house only uses gas for the stovetop and water heater


I’ve finished designing the retrofit and I’m starting to implement the measures. While the retrofit won’t be finished until later this year, there are some big lessons already.

Lesson 1 – We need to aim for comprehensive retrofits

You can make a home perform better though single measures like installing wall insulation. However, doing half the job will deliver far less than half the benefits. For example:

  • If you insulate a home but don’t draughtproof it, draughts will undermine your insulation; and
  • If you draught-proof a home but don’t insulate it and add mechanical ventilation, you might develop mould problems.

Designing a comprehensive retrofit means thinking about how various parts fit together. For example, the size of your heating system should be based on how insulated and air-tight you are going to make your house. This doesn’t mean that you need to totally retrofit your house in one go, but you ideally need to create a comprehensive retrofit plan upfront, even if you implement it over several years.

My retrofit will involve:

  • Replacing the ceiling insulation, pumping insulation into the walls and stapling underfloor insulation to the floorboards. While ceiling insulation tends to get the accolades, its actually pumping in wall insulation that will have the biggest impact on my building’s comfort and energy use.
  • Draught-proofing, including filling in a bunch of internal wall vents;
  • Replacing the single-glazed windows with uPVC double-glazed windows. This won’t just improve comfort and deliver soundproofing, it will also eliminate a major condensation issue;
  • Putting powerful fans in the bathroom and toilet; and
  • Replacing the electric resistive heaters with an efficient reverse cycle.

Lesson 2 – Retrofits are about comfort and health

A complete thermal retrofit isn’t cheap - mine will cost close to $30,000. However, that’s a bargain for totally transforming the feel of a house. I think it’s a huge mistake to try to sell retrofits as a way to save a bit of cash off your bills, it’s far better to compare it to the cost of redoing a kitchen, which averages over $25,000 and has far less of an impact on your life.

One of the worst things we can do is think about thermal retrofits in terms of the ‘payback period’ – the period over which the energy savings will pay back the retrofit. The health benefits of a retrofit totally dwarf the energy savings, and the intangible ‘comfort’ benefits are often the primary motivators for households. Selling a retrofit based on its payback period completely ignores the main reason that people retrofit their homes, which makes no sense. We don’t talk about the ‘payback period’ for putting in a smoke alarm, or even a granite kitchen bench, and we shouldn’t do it for thermal retrofits.

The other reason for putting less focus on energy savings is that as buyers become more sophisticated, the uplift in a home’s value is likely to be much larger than energy savings. In places like Europe and the Australian Capital Territory (ACT), where homes are required to disclose an energy efficiency ratings when they are sold, more efficient homes are sold at a premium compared to less efficient homes. This is likely to be a much stronger incentive for retrofits than the financial benefits of energy savings.  

Lesson 3 – Households need comprehensive advice 

I found it incredibly challenging to work out the finer details of retrofitting my home. Before I talked to anyone I developed a rough plan for the retrofit based on this excellent report from Sustainability Victoria, and the cost-estimates were pretty spot on. However, the devil was most definitely in the detail, and I had no idea where to start.

I engaged Tim Forcey to carry out a Victorian Residential Efficiency Scorecard assessment on my house. Tim confirmed that my house was an absolute energy disaster, but also showed that it was totally possible to get the home up to about 7 stars through a series of energy efficiency upgrades. I could get to 10 stars if I added solar PV, but that wouldn’t make any difference to the comfort of the house so I put PV into the pile of things I’ll consider later.

Figure 3. Tim Forcey points out stupid things in my house

I wanted to compare the Scorecard to NatHERS, so I engaged architect and energy expert Jeremy Wells from Tochi to carry out a NatHERS rating on the house. Jeremy modelled that upgrading the building fabric would take my house from 2.2 stars NatHERS to 7.1 stars. This would theoretically reduce the energy needed to heat and cool my home by 78 per cent, and when coupled with the shift from electric resistive heaters to a reverse cycle system I’ll theoretically use about 95 per cent less energy.

Figure 4. NatHERS ratings for my house – current and theoretical



In practice, the actual energy savings will probably be closer to 50 per cent for a very simple reason – my house is far colder than the NatHERS software assumes it should be. Back of envelope, I’d currently need about 12kW of heating just to keep my home at a comfortable temperature on a very cold day, and the house only has a fraction of that capacity. Again, a strong reminder that comfort and health are likely to be the major drivers for many retrofits.

The challenge I found was then converting the advice produced from the Scorecard and NatHERS assessments into actionable measures. How many reverse cycle air conditioners do I need? What capacity? What brand? What type of bathroom fan should I install? Who’s a good supplier? Who can I get to do the plastering? What do I do about that annoying wall that probably needs to be insulated from the inside?

In addition to the challenges of working out the details of what needs to be installed, it also became apparent very quickly how important the sequencing of upgrades would be. I’d love to just go ahead and put insulation into the walls, but I need to undertake electrical works, plastering and double-glazing before I pump insulation into the wall cavity. While the sequence of measures may seem obvious to an expert, it isn’t to a novice.

I was extremely fortunate in getting support on these questions. Tim, Jeremy and experts like Jenny Edwards from Light House Architecture and John Konstantakopoulos from Efficiency Matrix very generously provided me with advice on the retrofit. However, most households won’t have access to the top experts in the country, and the experts can’t give out advice for free. If we’re going to roll out retrofits at scale, we need to develop a new paid service.

Rating the energy efficiency of a building is a stand-alone service that is necessary for allowing people to compare the thermal quality of homes before they buy them. We need to formally recognise that there is an additional, separate service in providing households with a very detailed blueprint for retrofitting their house. There are already models for this kind of service overseas - in Germany well-qualified Energieberater give households detailed plans for retrofitting their homes, which the households then implement over several years.

Lesson 4 – Quality is king

It’s very clear that whoever provides households with a blueprint for their retrofit needs to know building physics in quite a bit of detail and have practice experience in seeing a retrofit through from start to finish. There’s currently a handful of genuine experts in Australia, so to roll out retrofits at scale we’ll need training and accreditation systems for retrofit experts.

However, retrofit experts will also need to have a Rolodex of quality providers. The many trades involved in a retrofit also need to know their stuff. John from Efficiency Matrix came round to do a thermal assessment of my house and found out that whoever installed the ceiling insulation back in the 1970s definitely DIDN’T know their stuff. The insulation is theoretically R1.5, which was pretty standard for that time. However, over 15 per cent of the ceiling had gaps in the insulation, which meant that the insulation had about 65% less impact than it should have, just R0.5.

Figure 5. Insulation with massive holes in it



Trying to do a retrofit on my home has been both incredibly challenging and humbling. Once the retrofit is complete, I’ll hopefully have some more insights to share.

We’re going to need to do a lot of work to create a vibrant retrofitting industry. However, the prize in terms of health and wellbeing improvements is huge. That’s why countries around the world have been hard at work over the last decade to create retrofitting industries. It’s time Australia caught up.


Rob Murray-Leach is Head of Policy with the Energy Efficiency Council

Connect with Rob on LinkedIn.

This article was originally published in the June edition of Efficiency Insight.