When Carlos Acuna and his family moved to Perth 10 years ago, they “quickly fell in the love with place”.
“We got our permanent residency, and recently our citizenship. We’ve just loved it here and feel really fortunate to be in a place like this,” he said.
Seattle averages between 4-8 degrees Celsius in winter, while Perth’s average winter temperatures are 10-18C, but the family found the houses they rented in Australia the coldest they had ever experienced.
“[The houses are] cold, they’re ice chests,” he said.
“We had very high electric bills in the summer to keep the house comfortable.”
Airtightness ‘virtually unheard of’ in Australia
After years in rented houses, both old and new and that were all hard to keep at comfortable temperatures, he decided to build a highly insulated, airtight house that used passive heating and cooling design to keep the indoor temperature at between 20-25C all year round.
He began talking to builders, but found that standards that were common in North America were not a part of most builds in Australia.
“We knew that we wanted a house to be built more towards an American standard, if you will, in terms of insulation and airtightness,” he said.
“Air tightness is maybe not as obvious, but if you have the best insulation in the world with gaps that allow cold air to escape in the summer, or hot air escaping in the winter, comfort in the house is going to be very difficult to maintain.”
No testing of energy efficiency standards required
He said that every new North American home is tested for airtightness using what is called a “blower door test”.
It measures the number of air exchanges per hour inside a house, showing how quickly cooled or heated air is escaping from the home.
In Australia, the current National Construction Code (NCC) requires new homes to be built to do 10 air exchanges per hour or fewer, but does not require blower door testing at the completion of a build to verify the standard has been met.
“These are energy efficiency measures that started in the US and Europe with the Iran oil embargo in the 70s,” Mr Acuna said.
“So today, a typical project builder in the US will achieve three air changes per hour, which is fantastic.
Mr Acuna said in Australia no testing is required, and he suspects many new builds are not even meeting the six-star energy standards.
“The challenge with those standards is they’re written in a way that makes them very unenforceable,” he said.
“Over the seven years [we rented] older homes that were built in the ’70s, and a couple of homes that were recently built to the six star standard, there was really no appreciable difference in performance.”
An extremely sealed home
After an extensive search, the Acunas opted for a German Passivhaus design which uses thick, insulated walls and double glazing with tight seals to create an extraordinarily airtight building that, when tested, allows only 0.6 air exchanges per hour.
“The German Passivhaus standard is the most energy efficient standard in the world right now,” he said.
The home is so airtight it needs mechanical ventilation to introduce fresh air and prevent mould, but it also means that a double storey, 200-square-metre, four-bedroom house uses just two small reverse-cycle air conditioners for heating and cooling.
While the build was much more expensive than a typical new home, its average heating and cooling costs — which fluctuate with the season — are around just $35 a month.
It allows the family to make the most of Perth’s climate while staying comfortable.
“When the weather’s nice outside, as it is for large parts of the year in Perth, we can open up our windows and allow fresh air in and out,” Mr Acuna said.
The house has two small split system air-conditioners — one upstairs, one downstairs — which can stay on for months in summer and winter, keeping the temperature consistent.
“We’ve been living here since January 2019 and we’ve never had a summer where this space is at more than 23 degrees,” he said.
‘Builders are doing this in the rest of the developed world’
Despite the energy saving, the high cost of a PassivHaus means it is probably not for everyone.
But Mr Acuna believes raising standards, and testing, on conventional builds could make a big difference in all new homes.
“The building associations are very hesitant to embrace some of these new standards like airtightness, and they’re trying to delay the government’s implementation as late as they can,” he said.
“But I do think that people are starting to hear more about this.
“Builders are doing it in the rest of the developed world, it’s just a matter of time before the builders here learn how to do it, and they’ll be doing it for the same cost that they’re building houses now.”
And he now enjoys winters without freezing.
“You wake up in the morning at five or six to take a shower and the house is at 18 degrees,” he said.
“In the first winter that was fantastic for us because we’d been living in homes that were at 10 degrees in the morning.”