Making our homes more energy efficient is easy, so why aren’t we all doing it?

A home built in Australia today isn’t suitable for a net-zero world in 2050.

Australian homes are hot in the summer, and walk-in freezers in the winter. Air conditioning and heating systems can keep us comfortable. But with rising energy costs, a cost-of-living crisis, and a climate emergency, we need to rethink how we build and thermoregulate our homes drastically. The technology to make our homes carbon neutral exists, and we have examples: In 1973, the oil crisis prompted the development of building energy standards across Europe.

The primary focus of the legislation was insulation, says Roberto Lollini, professor of building physics and research leader of the Energy Efficient Buildings at Eurac Research in Bolzano, Italy.

Double glazing and roof insulation became the bare minimum for all new buildings. But Lollini says making a home carbon neutral is not only about insulation. Over the decades, European legislation has added more requirements, and in 2010, having at least part of the energy consumption covered by renewables became mandatory for new homes.

Minimum insulation requirements did not emerge in Australia until the 1990s, and only in 2003 did the Building Code of Australia establish national standards for housing energy efficiency. Yet, Australian legislation falls far short of many other countries’ minimum building standards for energy efficiency.

“Building a very energy-efficient house is quite easy,” says Associate Professor Philip Oldfield, Head of School of the Built Environment at UNSW and a researcher in sustainable and low-carbon architecture. “You provide optimal insulation and ventilation, recover the heat in the winter, provide shading in the summer and generate energy from the rooftops.”

But he says Australian housing building regulations are 20 years behind many other developed countries, and even a house built today is not up to scratch for 2050 net-zero targets. “We need to commit that what we build now is suitable for our decarbonised future.”

From net-zero to carbon positive

The 2010 “Energy Performance of Buildings Directive” required European countries to ensure that all new buildings were nearly zero-energy by the end of 2020. A nearly zero-emission building (NZEB) has a very high energy performance, with the nearly zero or very low amount of energy required, being covered to a large extent by energy from renewable sources.

Germans have led the way with their Passivhaus – a super-efficient, ultra-insulated, airtight building with excellent ventilation and heat recovery systems. Heating and cooling are almost unnecessary in a Passivhaus. “Ideally, people should not need an active heating or cooling system,” says Lollini.

A nearly zero-energy home is oriented and shaded in such a way that it maximises solar exposure in the winter and decreases it in the summer. It is airtight and has excellent thermal insulation at the roof, walls, and between floors to prevent unwanted heat dispersion; it has air filtration systems as well as natural and mechanical ventilation systems. High-performance windows, such as triple glazing, let in plenty of natural light while keeping the internal temperature stable. Efficient artificial lighting and appliances reduce the energy required, which solar panels produce.

In 2021, the European Commission proposed revising the directive and moving from NZEB to zero-emission buildings (ZEB) by 2030 to push further the decarbonisation process. Households still represented 27% of final energy consumption in Europe in 2020, according to Eurostat, the statistical office of the European Union. 

Zero-emission homes release no net carbon dioxide into the atmosphere during their operation. This means that the house annually generates as much energy as it needs for heating, cooling, hot water, lighting and household appliances.

But Lollini believes that to achieve our climate targets we must move beyond the zero carbon benchmark by making houses able to make additional “positive energy contributions”. A carbon-positive home produces more renewable energy on-site than the home requires and feed that excess back into the grid. “We are starting to see buildings as an active part of the urban environment,” he says. “As such, they can produce, store and exchange energy with other buildings, infrastructure and e-mobility system.”

How to make your home more energy efficient

The technology is there for it. From water-repellent building insulation made from popcorn as a replacement for petroleum-based materials to smart windows and 3D-printed insulating facades, the field of building energy efficiency has seen some great innovation.

But if the idea of retrofitting our home to make it zero-emission or even carbon positive seems unreachable, there are steps we can take to improve our home’s energy efficiency and make it more comfortable, says Oldfield. “Upgrading a poor-performing house can be challenging, but there are some small things you can do to improve it.”

There are three main issues with Australian homes, he says. “We still rely on single glazing; our houses are under-insulated and very leaky.”

He says that roof insulation is a fairly simple job, which doesn’t require you to move out and can be done with a relatively modest budget. “The best thing you can do is to insulate the roof because that’s where the heat goes.” 

Another simple and inexpensive method to upgrade your home is improving air tightness by applying mastic around windows or gaps in the building fabric.

To achieve zero-emission standards, most Australian homes would need deep retrofitting, which involves a much more significant investment. “You can’t rely on the private sector to retrofit all these homes,” Oldfield says. “There has to be government support.”

Loans, tax breaks and grant schemes have sparked a renovation wave in Europe.

In Germany, incentives are offered to self-builders, developers and first-time homebuyers. Homeowners who want to upgrade their property can deduct 20% of the costs of approved technologies, such as improved windows and external doors, from their tax liability to make a more sustainable home. In Italy, the “superbonus” scheme allows homeowners a tax credit of up to 110% of the cost of retrofitting their homes.

Oldfield says Australia should also come up with ways to encourage homeowners to upgrade their dwellings and invest in retrofitting public buildings such as schools, hospitals and offices. “It’s not cheap, it is not cheap, but you will get amazing buyback.”

One obvious benefit of investing in buildings’ energy efficiency is a significantly reduced energy bill. But there are also indirect benefits, Oldfield says. “We’ll be more comfortable at home. We will get sick less. Our physical and mental health will improve. There’ll be reduced absenteeism from work and will increase productivity.”