Stephen Cuthbert says the 'passive house' approach to home design can be off-putting or unappealing to some.
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"Some people get a little bit worried, thinking, 'oh, that sounds fancy, sounds European, I can't afford that'," he said.
"But we liked that they're very low energy, you can control your indoor air environment, you have no leaks or draughts, it's very steady temperatures all-year round.
"It's well-insulated, comfortable and quiet, and there's no allergies because it's filtered air."
The end result is what's being billed as the Illawarra's first certified 'passive house' duplex.
Passive house design principles are met via a specific criteria; a series of minimum performance requirements to achieve certification.
The new three-bedroom, three-bathroom duplex is located at 32B Rae Crescent, Balgownie.
It has been built and certified to the German Passivhaus Standard to ensure an energy-efficient lifestyle.
Sydney-based Mr Cuthbert and wife Charlotte bought the property in 2015, and later set about undertaking a knockdown-rebuild.
"At the time, rather than renovating, we thought we'd just build two new houses and set ourselves up for the future," he said.
Mr Cuthbert said they wanted to embrace better building techniques, as well as encourage improved indoor air quality, low energy and a better lifestyle.
'It just happened to be that it was Passivhaus that ticked all the boxes for those requirements," he said.
Passivhaus, which translates as 'passive house', is a housing performance standard conceived in Germany in the late 1980s.
The approach is based around five key elements - insulation, high-quality windows and doors, eliminating thermal bridges, air-tightness and heat recovery ventilation.
It utilises a combination of high-performance glazing, insulation and an airtight building envelope to regulate a home's internal temperature without relying on artificial heating or cooling.
Mr Cuthbert said the property would now serve as an investment, but they planned to live there one day.
He said they also planned to monitor the property's performance using energy sensors.
Builder Pat Furci of Havenview Homes said construction took eight to nine months to complete.
He said tenants are expected to move in next week.
Mr Furci said this was his first experience working on a passive house duplex.
"Initially it's pretty daunting to go into something that you've never done," he said.
"I've been building for probably 30 years, and when you're used to doing things a certain way, and then having to do them differently is a bit tricky."
He said the cost of building this style of duplex is about ten per cent more than a standard build.
"It's a challenging build because it's new," he said.
"But over time, once more builders get into it and more people are aware of it, it could be more mainstream.
"Then it'll be more familiar and easier to work with, and have materials that are more readily available."
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