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In short:
A change to the National Construction Code means all newly built homes will need to have a minimum thermal efficiency rating of seven stars.
Canberran Bianca Knox's 1970s house isn't up to that standard, but DIY upgrades have increased its energy efficiency from 2.6 stars to 4.7 stars.
What's next?
The code will require new builds to meet the minimum efficiency rating, with all jurisdictions except Tasmania to adopt the changes.
When Bianca Knox was house hunting, she quickly fell in love with a 1970s suburban Canberra cottage.
But after moving in, she discovered a glaring issue.
"You'd have to walk around wearing jumpers and scarves at all hours – it was very cold," she said.
With a chronic health condition triggered by cold temperatures, finding ways to heat her home in Canberra's harsh climate without breaking the bank was a priority.
So the building designer got to work.
"The first thing we did was remove the fireplace and patch that hole in the ceiling," she said.
"Any holes in the ceiling are a really crucial point of heat loss in any home."
She filled gaps in the walls and cornices with foam and a caulking gun, replaced old exhaust fans and sourced some salvaged insulation.
The changes have increased the energy efficiency rating in her home from 2.6 stars to 4.7 stars – equating to a 50 per cent reduction in energy to keep it at a comfortable temperature.
It has also sliced almost $150 off her winter power bill.
"Since then, we've really felt the difference in how heat holds in the room," she said.
"And we've managed to only use a small oil heater to keep the room up to a good temperature."
Experiences like Ms Knox's are common in southern Australia, where research suggests four out of five homes get unhealthily cold.
But it's hoped recent changes to the National Construction Code will shift the dial.
A new benchmark
New builds across most of the country are now required to meet a minimum seven-star efficiency rating, up from the previous six-star benchmark.
The scale is used to assess a building's thermal performance.
The changes are yet to come into effect in South Australia and Western Australia, while Tasmania will not adopt the new standard.
Canberra sustainable building expert Jenny Edwards said the new standards represented a "significant jump" in energy efficiency and comfort.
"A seven-star house requires 30 per cent less energy per square metre to heat and cool across the year … [which] equates to hundreds of dollars in savings," she said.
Master Builders Australia director Alex Waldren said meeting the new benchmark could add between $5,000 to $20,000 to the cost of a new build.
"The requirements include more insulation, they include better quality windows, they include better thermal fabric wraps – that's where the cost is for people," Ms Waldren said.
Building a seven-star home
Ms Edwards said achieving a seven-star rating without a hefty price tag was achievable with good planning and design.
"The main thing I stress again and again is to use the sun — that doesn't cost any extra," she said.
She said homes should be oriented to make the most of the northern sun, with adjustable shading to allow living areas to soak up warmth in the colder months.
Ms Edwards said minimising air leaks and insulating thoroughly also made a big difference.
"It's not rocket science, it's back to basics," she said.
"The gaps in Canberra homes add up to often be equivalent to a 40 centimetre square window being open all year long."
Features like double-glazed windows are a big benefit in cold climates too – and they are cheaper than they once were.
"A little bit of investment up front can save you a lot of money during construction and masses of money during the life of the home as you run it," Ms Edwards said.
Ms Edwards acknowledged the new standards would require a shake-up for the construction industry.
"Builders in the past typically have been able to use the same designs again and again and again and plonk them on blocks without thinking about orientation," she said.
"Five-star, six-star houses were easy to do with pretty much any design.
"Now this leap to seven stars will require builders to change the design, so there's quite a lot of opposition because of that."
Despite the move to seven-star builds, Ms Edwards said homeowners should not discount retrofitting old properties to make them more efficient.
Bianca Knox is eager to keep upgrading her Canberra cottage, including installing more insulation and saving up for double-glazed windows.
She hopes to eventually get her home to a seven-star efficiency rating.
"It has the potential to be a super comfortable house that doesn't really require much heating at all, which is the goal," Ms Knox said.