How an architect turned her ageing bungalow into a climate-controlled oasis

When Urban Core managing director Dominique Gill founded her construction company eight years ago, she had a mission that was twofold: improve sustainability and increase diversity.

Gill decided to use her own home renovation in Northbridge as the perfect opportunity to execute her case.

“It was very important to put my money where my mouth is,” Gill said, who is also an architect.

As the construction industry is one of the worst offenders when it comes to greenhouse gas emissions and waste, Gill said she wanted to show there was a better way.

“It was really important to me if I was going to build my own house, that I made a little case study of what’s actually possible in construction,” she said.

After exploring different sustainability options, she decided to experiment with PassivHaus, a German energy-efficiency standard, which does not require traditional heating or cooling because of its thermal efficiency due to its airtightness and insulation.

With the help of her university friend Isabelle Toland of Aileen Sage who designed the extension of her 1924 Californian bungalow, adding a living room, a new kitchen, a natural pool and basement.

The main material Gill opted to use was cross-laminated timber – or CLT – which uses engineered wood that is glued with at least three layers in different directions – making it a more sustainable material and providing better thermal insulation.

All the windows are double-glazed, including the existing ones in the original part of the home, which were replaced.

But the design and build did not come without its unique challenges, including a more than century old tree that they were not allowed to remove.

“I knew she’d [Isabelle] come up with a really interesting design. Also, the particularity of this place is the brush box tree, which has a 12-metre canopy and is deemed significant to the streetscape of Northbridge,” Gill said. “It’s more than 100 years old. I thought it was quite special.”

As a result, the entire extension was designed around the tree to preserve it and keep true to Gill’s sustainability mission.

The floors in the extension also have PIR – or polyisocyanurate – insulation panels to prevent damp rising and further insulate the home.

The home also has a built-in dehumidifier to prevent mould, which can cause illnesses, and a heat recovery unit, which ensures the right amount of fresh air in the house.

“When you have a really airtight space, that’s really great. That means that the heat doesn’t escape, and the cold doesn’t come in and vice versa,” Gill said.

“But that can also create quite a stale environment. So it’s a bit paradoxical because you’re trying to do something good, but you’re creating a new problem and the problem is generally, the levels of oxygen and air freshness.”

Gill said these features not only improved the sustainability of the home during its construction and running of it, but added to the wellbeing of her family.

“What I loved about PassivHaus, it is not just my bills are going to be lower, it’s also a wellness rating … because sustainability is also about wellness.”

Does the home pass the test on a hot summer’s day or in the depths of winter without air-conditioning?

“It’s supposed to stay within a range of like 16 degrees to about 26 degrees all year round, and with only 10 per cent of the time when it’s outside that range,” Gill said. “We really feel that difference, and it’s comfortable.”

Gill is proud to have achieved a sustainable extension of her family home using her female-founded and led company, where 50 per cent of staff are women.

“If you have a group really diverse in identity, you generally will get a lot of diversity of thought, and diversity of thought and cognition is what gives you better collaboration, better creativity, innovation and profitability,” she said, noting they also better serve the public when they are better represented too.

“Construction has this real big image issue, which is really ironic because while we’re not heart surgeons, as I’m often told, you and I are sitting in this house right now. I’m not really worried whether this is going to fall on our heads,” Gill said.

“We go into a tower in the city, catch the lift to level 41. We’re not thinking, ‘Well, I hope that lift shaft will hold’ – we just take it for granted, almost, how important the work builders do is.

“We do protect people’s lives every day, and we trust construction with our lives every minute of the day without even thinking about it.”