Harrison Case Study
No heating or cooling bills at Strine home in Harrison
‘We always love coming home when we’ve been away. It’s just a great place to live.’
A former accountant, John Gifford loves crunching numbers. He knows all the vital statistics for his passive solar ‘Millennium’ home in Harrison and, more importantly, exactly how much it is saving him each year on his energy bills.
‘We paid a total of $1350 for gas and electricity in 2013,’ said John. ‘We use gas hot water in the laundry and two bathrooms and electricity for everything else. But that’s it. In total we used 22,500MJ last year. But in winter, for example, gas cost us only $250. Because we don’t have to turn on any heating [or cooling] in the house, we have a very small energy bill compared to those using gas for heating.’
Given Canberra can go through very cold spells; it fell to -10° twice during the 2013 winter, being able to keep the house warm without turning a heater on is something very few can claim but many would love to achieve. And in summer, when it’s 40°+ outside, John and his wife Elaine say they are completely comfortable inside where the temperature in late afternoon might rise to 28°, but no higher. And that’s before they’ve felt the need to turn the overhead fan on in the main living room, which acts as an evaporative cooler.
Completely eliminating the need to turn on heating and cooling in Canberra’s tough climate of extremes is exactly what Strine Environments’ passive solar buildings, such as the ‘Millennium’, are all about. And it all revolves around four basic principles:
- Building the house so it faces north to maximise winter sun, and eliminate summer sun with a vine-covered pergola.
- Creating thermal mass on the inside using concrete floors and walls that absorb winter heat and slowly release it in the evenings.
- Putting a doona over the house at night by building high-level insulation into wall panels and ceiling, as well as around the floor slab.
- Correctly glazing different aspects so the sun is either absorbed or reflected.
The right house for Canberra’s climate
Returning to Canberra after a period living away, John and Elaine were looking to buy a property but were unimpressed with everything they saw. Interested in the principles of passive solar design, they looked at various solar houses before settling on the ‘Millennium’ designed by local architect, Ric Butt, of Strine Environments.
‘It ticked all the boxes for us,’ said John. ‘We’d learned the value of winter sun and thermal mass living in a house in Deakin. It was so warm in winter during the day but lost all its heat at night because there was no insulation or thermal mass to hold it. So those aspects were critical to us and we found them in this design.’
John and Elaine also liked the open layout – the kitchen is part of the generous main living room – and the fact the design is ‘practical, flexible and functional’. ‘We haven’t wasted space on anything that doesn’t need it, but have more than enough where we want it, in the living spaces. We can easily accommodate our large extended family when they come to stay.’ John said he and Elaine could also do separate things without bothering each other.
‘The design is not cluttered,’ said John, ‘there’s a simplicity to it that’s very effective and I also like the effect of the curved roof.’ Elaine said people always gush about the garden when they arrive, but are even more impressed when they step inside and take in the generous space and open layout.
Both John and Elaine find the interior space ‘very calm and relaxing’. ‘You really are insulated not only from the weather but also the noise that comes from neighbours and traffic.’ This sense of separation is due to the high mass or ‘solidity’ of the building, but it is enhanced by one other design element of a Strine house: the ceiling is painted a pale blue to promote calm. Colours are very important within a Strine home and have specific roles to play. For example, the northern wall ends of the internal wall should be a dark colour to maximise how much sun is absorbed in winter also reducing glare in summer.
A northerly aspect
As one of the first homes to be built in Harrison back in 2005, John and Elaine had their pick of sites. With the help of Ric Butt, they chose a long 630m2 block that while narrow, had the perfect northerly aspect to let in the winter sun. It allowed them to maximise the benefits of the rectangular ‘Millennium’ design, as the entire north side of the house is glass.
Extensive northern glazing the glass allows maximum sun and heat in winter and to stop the hot summer sun flooding the space – the design includes a vine-covered pergola that is a stunning feature throughout the summer and autumn months, and provides a beautiful spot for the couple’s extended family to enjoy a meal together in summer. John believes the house wouldn’t work without it. In addition, the windows have thick Roman pull-up blinds that act as a barrier when needed in the height of summer and winter.
Living inside and outside
The garden is a critical part of the overall design of a Strine house, and not only works to cool the air and reduce wind velocity, but also allows for indoor/outdoor living in the shoulder seasons of autumn and spring when sliding doors to the north and south are pushed right back, and the space effectively doubles. Elaine loves the integration of the garden into the house. ‘I love that we’re inside but living outside too’.
The house is nestled within a lush garden – a mix of natives and cottage plants – that protects the house from both neighbours and the elements. Dense tree and shrub plantings in front of the house screen the front door and create a protected entry, which only reveals itself when you arrive. This, along with the fact the front door is offset 90° to the street, creates a very private space.
The integration of house and garden is a fundamental part of a Strine build: Strine houses offer a holistic site design – a house and a garden – the design principles don’t stop at the outside of the house but rather continue to the boundaries of the block.
For John and Elaine, this house not only offers a high level of comfort within a secluded and beautiful garden, it means never having to pay for heating and cooling ever again. They can do their bit to save the environment while also saving money at the same time.
More than anything, however, it is a family home to share with children and grandchildren, who not surprisingly, visit often.
Building innovations in a Strine house
If the current energy efficiency rating scheme used for houses in Canberra allowed for the innovations used in a Strine building, John and Elaine’s ‘Millennium’ home would score ten stars. Currently, the scheme is based on typical brick veneer homes, which don’t employ passive solar design principles.
Some of these innovations include:
- High insulation is achieved due to the use of insulated precast sandwich concrete walls, a concrete slab that keeps the floor at a constant 18-20° (this can be polished and show pigment if desired or carpeted), as well as insulation in the roof and foundations. All these elements work together to completely isolate the inside of the house from outside weather extremes.
- Solar chimneys can be opened to quickly flush out hot air in summer.
- Slab-edge insulation sees the concrete walls extend 1m below the house floor and effectively ‘hug’ the earth, which provides another form of thermal mass (infinite mass).
- Correct orientation allows winter sun to flood the rooms; it hits 4.5m within the 6m-wide space. This eliminates the need for traditional heating such as ducted gas. In summer, a vine-covered pergola protects the house from the summer sun. So much glass on the northern side of a traditional building would overheat the property, but on a Strine building, it is a fundamental part of the passive solar design principles employed.