A Passive House in Toorak that the client wanted built in Mt Gambier Limestone was an interesting challenge for John Wardle Architects. The house will feature as part of the Passive Australia Passive House Association Symposium in Sydney on 26 September.
When I speak to people about Passive House (passivhaus), they think of a box with small, sealed windows and a pitched roof. This is an unfortunate and common misconception. Although it may be easy to meet the Passive House requirements with the boxed, small windows design, it is not the only design available and is not the only design used by certified Passive Houses built today. There is no standard “look”; a Passive House can be any building. Upon hearing this, the usual response I get from people is a look of disbelief.
One building that is challenging this misconception is a three level dwelling, 675 square metres, located in Toorak, Melbourne. Thanks to the client’s passion for sustainability and contemporary architecture, John Wardle Architects was able to design a unique, energy efficient home for a healthy living environment.
This house was first brought to my attention when I saw a presentation in Melbourne at the South Pacific Passive House conference in May, 2018, about the building known as Limestone House. As an architect and Passive House enthusiast, it made me happy to see that I have been spruiking the correct information about Passive House. This home was not only energy-efficient, it was nurturing a healthy, self-sufficient environment.
Starting the project in 2015, John Wardle Architects had to design the house with not only Passive House certification in mind, but it had to also meet the Living Building challenge criteria. This design brief was to be primarily self-sufficient, managing its own water, wastewater, complete photovoltaic system and battery storage.
Once the design got closer to construction, the proposed cladding of Mt Gambier limestone provided the project with its memorable name. The limestone was chosen because it is considered a low maintenance cladding that will weather over time, changing colour to a silver-grey.
Acid rain can be a problem for limestone
The advantage of using limestone for the external walls is that it is considered one of the most durable natural building materials available in abundance throughout the world. This can be seen by the ancient structures that still stand today, such as the pyramids of Egypt. It has also been considered to be versatile and aesthetically pleasing. However, limestone can corrode, in particular, if the rain is acidic. In environments with highly acidic rain this cladding would have to be well maintained to not significantly wear away over time.
The limestone cladding is well suited for the location of the development as high volumes of acidic rain is not a usual event in Victoria, Australia. It is believed that acidic rain more commonly impacts areas which emit large amounts of sulphur dioxide and nitrogen oxide such as the south-eastern coast of China, Taiwan and other areas around the globe further away from Australia.
Limestone House is in an amazing dwelling that has more features than its unique cladding option. It has a flat roof, various room shapes, curved walls challenging thermal bridges, adequate insulation and ventilation systems. The required detailed analysis of all aspects of the design for this Passive House is not of the ordinary kind.
This unique house is not the only one in the market pushing typical design boundaries and succeeding in developing impressive passive housing. Montessori School, a school in Germany, was designed and built back in 2004, with a two-storey, organically shaped building that appears to grow out of the ground with a curved green roof.
The first ever office tower to achieve Passive House, RHW.2 in Austria, also has a curved facade and In Denmark, the local energy suppliers, SYD Energy, headquarters are in a round building. Closer to home, In New Zealand, a long narrow residential house was designed with overhangs on the North to allow for a large glazed area between the lounge space and outdoor pool.
With passionate, creative individuals and companies willing to push limits to get the perfect, sustainable building, a Passive House build can be so much more than a box house with small windows and a pitched roof.
Cyril Vibert, a design team member for the Limestone House and a sustainability consultant at Umow Lai, based in Melbourne, will step audience members through some of the challenges of Limestone House.
Kylie Mills is a registered architect, director of BluKube Architecture, and director of Australian Passive House Association. Shanice Sime is a certified Passive House Consultant and a Sustainable Design Engineer