Scorching summers, chilly winters: The thermal challenges of Aussie rentals

Australia’s private rental housing sector lags behind many other developed nations when it comes to thermal comfort and energy efficiency. 

With a significant proportion of rental properties built before the introduction of minimum energy performance standards in 2003, many homes struggle to maintain comfortable indoor temperatures. 

Poor insulation, inadequate shading, single-glazed windows, and urban heat island effects all contribute to overheating in summer and excessive cold in winter, leaving renters vulnerable to energy hardship.

While some states, such as Victoria and the ACT, have taken steps to introduce minimum energy efficiency standards for rental properties, Australia as a whole still lacks comprehensive policies to address these issues. 

In contrast, other countries have already implemented stringent requirements to ensure rental properties meet energy efficiency and thermal comfort standards. 

Given the escalating impacts of climate change, rising energy costs, and the growing number of renters experiencing energy hardship, urgent reforms are needed to improve the quality and performance of Australia’s rental housing.

In this interview, Dr Sarah Robertson, Centre for Urban Research, RMIT University and Prof. Trivess Moore, Post-Carbon Research Centre, RMIT University, explore the key factors that contribute to poor thermal performance in Australian rental homes, the limited options available to tenants to improve their living conditions, and the policy changes required to ensure rental properties provide a comfortable and sustainable living environment.

Architecture & Design: How does Australia’s private rental stock compare to other westernised countries in terms of thermal comfort and energy efficiency?

Sarah Robertson and Trivess Moore: We know that the quality and comfort of housing in Australia is typically worse than what is delivered in many other developed countries, including our private rental stock. Australia was late to introduce minimum performance requirements for new housing.

Much of Australia’s housing stock was built before the introduction of minimum energy efficiency requirements in 2003 through the Australian Building Code, now the National Construction Code. In Victoria, for example, a study found that the majority of homes built prior to the early 2000s perform at about 1.8 Stars, so not well! 

If zero stars is like being outside and 10 stars is living in a home that requires no mechanical or active heating or cooling to keep its occupants comfortable, 1.8 stars is a poor state of affairs. It means a house that is hard to keep warm in winter, and cool in summer, and large energy bills. 

Research from 2008 that compared Australia’s 5-star standard with housing in the USA, Canada and the UK found that housing in these countries was significantly out-performing the then 5-star standard (most states and territories now mandate 6 or 7 star minimum for new builds). 

And other research has found that we’re also not building new dwellings to the standards that are set and there are very few checks and balances to ensure that we do. 

Increasingly developed countries are introducing or improving minimum performance requirements for private rental housing. There have been some policy changes in Victoria and the ACT to set minimum requirements for private rental housing but on the whole we need to do more to get private rental housing to a higher quality and performance standard.

Energy hardship is a real and troubling issue in Australia, with research suggesting that 40% of households who rent may be experience energy hardship, unable to heat/cool their home sufficiently or pay bills on time. 

What are the key factors that make Australian houses, particularly rental properties, prone to overheating in summer?

Multiple factors can play a role in a dwelling overheating. There are some really basic things which if missing can make a house really hot to live in during summer. This includes a lack of external shading to keep the sun out, the amount and type of glazing – in particular our long history of using large single glazed windows means we have significant weak points in our home which allow heat to enter in summer.

Even things like the gaps and cracks around a leaky home or the colour of the roof can contribute. Dark colour roofs for example absorb a lot of heat. Insulation is also another key one but until the early 1990s there were no requirements for insulation at all! 

The external environment surrounding a home also contributes to how well it manages summer heat. What this means is that it is hard to keep the heat out in summer and occupants then have to rely on air conditioning to try and stay cool. 

To what extent do current building regulations and energy efficiency standards in Australia address thermal comfort for renters?

Australia has very few regulations to address thermal comfort for renters. Properties built more recently have to meet higher energy efficiency requirements under the NCC, but the majority of Australian housing stock was built prior to this, as I mentioned above. Newer 7 star homes will perform much better than older housing but will still not be comfortable all the time during summer and will still need air conditioning to maintain a healthy indoor temperature. 

Apart from the ACT, there are few minimum requirements for thermal performance of rental properties, and no disclosure of how a dwelling performs at the point of sale or lease. There is also no requirement to improve the quality and performance of existing housing. However, in other jurisdictions there are requirements to improve the minimum performance of rental housing such as in the UK.

What measures can renters take to improve the thermal performance of their homes - particularly if they are unable to make structural changes - and how effective are Victoria and the ACT’s minimum energy efficiency standards for rental properties in improving summer comfort?

Although they are being discussed, in most states and territories there are no thermal performance standards for rental properties across Australia. Beyond temporary changes, tenants therefore have few opportunities to make changes to a property to improve its thermal performance. 

If you live in the ACT, rental properties without ceiling insulation or insulation below an R-value of R2 are required to have this installed by November 2026. Other states are considering this requirement, but have not yet legislated it. In Victoria and Tasmania, there are minimum requirements for a fixed heater to be installed in one room, but this doesn’t include cooling. 

In terms of what tenants can do, it is important to try keep heat out for as long as possible when it’s hot, so external shading, or if not internal shading, where that can be retrofitted will help. Fans are a good and low-cost option that provide a cooling effect. You can also get films which you place on a window which can give a double glazed window like performance at a much lower cost. However, renters are generally limited in what they can do with any permanent changes often requiring landlord approval.

If they feel comfortable, tenants could also speak with their landlord or real estate agent about having a Residential Efficiency Scorecard assessment or other energy efficiency assessment carried out. This is an appraisal of the home energy performance and comfort. Best to check your local council or state government energy efficiency schemes. Many states and local councils also offer rebate programs for sustainability improvements for rental housing and you should explore what financial support might be available.

What policy changes would you recommend to ensure that rental properties provide adequate cooling and thermal efficiency?

Minimum thermal performance or energy efficiency standards for rental properties and the disclosure of a property’s energy efficiency performance are important to raising standards and we have seen them work well in other locations. However, these need to be introduced to ensure housing unaffordability issues are not exacerbated. We also need to make sure that there is a strong retrofit industry which can deliver the right type of retrofits to improve outcomes for occupants rather than just what might be seen as ‘easier’ or ‘cheaper’ options.

How do factors such as urban heat islands and climate change exacerbate the issue of overheating in Australian rental properties?

Climate change is seeing heat events last longer, happen more frequently and becoming more intense. Climate change and urban heat islands, where there is a build up of heat in a built-up area, need collaborative and holistic urban planning and housing governance responses. Research has found that the difference between a well tree lined street and a street without trees during a heat wave can be up to 15 degrees different. 

This is significant as it means that if you don’t have that initial nature defence you then are at risk of being in a much hotter home which will take much more energy to cool down in summer even with air conditioning. 

What role does insulation, glazing, and building orientation play in maintaining a comfortable indoor temperature, and how common are these features in Australian rentals?

Insulation, glazing and building orientation all play different parts in how a home performs thermally, or how it manages heat flows in and out of a home. For new builds, getting orientation right is a fundamental part of passive design. Depending on your climate, how a building is insulated and how, where and the type of glazing all play a role in how hot and cold a home gets without turning to active heating and cooling. 

Are there cost-effective retrofitting solutions that landlords and policymakers should consider to improve thermal comfort in existing rental stock?

The best retrofit solutions for a property are tailored to that property and its local climate, so it’s best to get an independent energy efficiency/thermal performance assessment carried out, such as a Residential Efficiency Scorecard assessment. Local and state government often offer rebates on these assessments, so look out for these. 

We know that as a general rule of thumb you will want to make sure you first seal up all gaps and cracks, then look at installing or improving ceiling, wall and floor insulation, ensuring good quality internal blinds and external shading devices (including nature) before thinking about some of the more costly actions like secondary or double glazing.

How do Australia’s rental laws and incentives compare to international examples where stricter energy efficiency regulations have been introduced?

We know that there are some locations where there are requirements for rental housing to meet minimum performance requirements. Where they don’t landlords need to make changes before the property can be rented out. 

This helps give renters improved housing outcomes and makes it clear to landlords what the expectations on them are. We are a little late in Australia in starting to introduce some of these requirements but we can learn from how these types of policies have been implemented overseas – we don’t need to reinvent the wheel.

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