Talina Edwards Architecture recently won the Sustainability Medal at the 2019 Architeam Awards for the Owl Woods Passive House project, and was also an official finalist in the New Home Category at the 2019 Sustainability Awards.
Owl Woods Passive House has been described as one of the most unique and beautiful Architecturally-designed Passivhaus homes in Australia.
The owners wanted a ‘tree-change’ home that was ‘just-enough’ in terms of size, whilst also being comfortable, sustainable, functional, flexible, healthy and beautiful. The architectural response was inspired by the surrounding bushland and farming land. The design echoes a cluster of farm-sheds or birdhouses, whilst also being reminiscent of a Scottish Village where the owners previously lived.
Located in the lovely regional Victorian town of Trentham, with an altitude of 700m above sea level, the area has weather that varies between snow in winter to summer temperatures reaching 40 degrees celsius.
For the new home to be climate-responsive, comfortable, sustainable and energy-efficient, the decision was made to design and construct the home to meet international passivhaus standards. This cutting edge approach to high performance homes is still new in Australia - the Owl Woods Passive House is in line to be the 5th certified Passivhaus single-detached home in Victoria, and 10th in all of Australia.
The Passivhaus standards allow for stable indoor temperatures and a healthy indoor environment with low running costs.
This is achieved by:
- Well insulated building envelope
- Airtight envelope
- Really great windows (that are openable for natural ventilation when the outdoor temps are desirable!)
- Controlled Ventilation
- Elimination of Thermal Bridges in the structure
- plus orientation for solar gain in winter with appropriate shading for summer.
The integration of Passivhaus standards with biophilic design enriches the experiences and wellbeing of the occupants. Generous visual and physical connections to nature, natural light and materials are integral to the design, whilst the contemporary pavilion style layout creates diverse indoor environments for its users to experience.
The locality is known as “Owl Woods”, and the home appears as though a collection of birdhouses are sitting in the native woodland. The pitched roofs stretch out to the north in a unique ‘birds-beak’ shape for summer shading. The orientation of the house is slightly north-west due to the ‘building envelope’ specified for the site – in response the roofs fold down on the western sides, forming wings to shelter each pavilion from afternoon summer sun. External blinds, and deciduous planting also help shade the house at different times of the day and year.
The home takes advantage of the winter sun to provide passive heating to the centrally located living areas, and the bedroom/bathroom zones to each side, which are connected by functional linkways and courtyard spaces which perform as outdoor rooms. The modest sized home has a couple of ‘bedrooms’ which are flexible as guest rooms or as everyday office/study/living areas.
Rather than just being ‘tin sheds’, lovely radial-sawn native timber cladding was introduced to complement the grey corrugated steel, and soften the overall feel of the home and create that connection back to the surrounding bushland. Materials were chosen that are natural, healthy, durable and sustainably sourced, relating back to the Australian landscape and minimising embodied energy wherever possible.
Designed to fulfill both the physical and emotional desires of its occupants, the Owl Woods Passive House is a unique blend of Biophilic Design and Passivhaus Standards of Construction. In this aspect, it really is a pioneer project for Passivhaus homes in Australia.
What was the brief?
The owners wanted a ‘tree-change’ home that was ‘just-enough’ in terms of size, whilst also being comfortable, sustainable, functional, flexible, healthy and beautiful.
How is the project unique?
It will be the first certified Passivhaus project in Australia designed by a woman architect (who is also a certified passive house designer.) the Owl Woods Passive House is in line to be the 5th certified Passivhaus single-detached home in Victoria, and 10th in all of Australia.
The Owl Woods Passive House is a unique blend of Biophilic Design and Passivhaus Standards of Construction - a balance of creative design outcomes which focus on how the occupants will feel in their home, along with the integration of building science which delivers a high-performance home. In this aspect, it really is a pioneer project for passivhaus homes in Australia.
Who are the clients and what's interesting about them?
David and Yvonne are British and have lived in many homes all over the world - yet here in Australia with our mild weather conditions, they've never lived in houses so uncomfortable and unsuited to the climate. We honour and respect our client's decision to be early-adopters of the international certified Passivhaus standard for their new home.
“After many renovations we'd always wanted to build a house from scratch. High on our priority list was sustainability, for a variety of reasons, but were not quite sure what that could/should entail! Key to us was engaging local firms and, during this search, the idea of a house with good solar orientation was suggested and this soon developed into a full blown Passive House (still with the solar orientation, but now with awesome thermal properties and air tightness) was suggested and it quickly took hold as the ideal way to build our new house - given the climate, rising energy costs and achieving ‘comfortable’ living. When we've been living in the house for a year we'll be able to gauge the impact on running costs, but we're expecting to be pleasantly surprised.” - Home Owners
What are the sustainability features?
WHAT IS A PASSIVHAUS?
Buildings that are designed and constructed to meet the strict Passivhaus standard are the most comfortable, healthy, durable and energy-efficient buildings in the world.
In everyday terms, this means they are:
- Comfortable all year round with indoor temps of 20deg - 25deg C, and no drafts
- Healthy due to a constant supply of fresh air that has been filtered, so minimal dust and pollutants enter the home, and C02 and VOC levels can be kept at safe levels. Healthy due to human comfort levels. Healthy due to prevention of mould.
- Durable as the buildings have to meet such a high standard that they are made to last
- Energy Efficient due to low heating and cooling requirements
Australians have been living in “wooden tents” for so long, Australia is about 30years behind the northern hemisphere when it comes to worlds’ best practice for building. Our homes are so poorly insulated and drafty.
We need to “build tight and ventilate right”. Controlled ventilation is key. This achieved by Mechanical Ventilation with Heat Recovery (MVHR).
- Well insulated building envelope: continuous insulation to roofs, walls and floors
- Airtight envelope: incorporating the use of air-tight membranes which wrap the building frame and are taped up
- High quality windows: thermally-insulated window frames with high-performance double/triple glazing (that can be openable!)
Elimination of Thermal Bridges: i.e. ensuring a steel beam doesn’t pass from outside the building to inside as the outside temperature will then travel along the steel to the inside
- Controlled Ventilation: mechanical ventilation with heat-recovery
- Form Factor: an awareness of the implications of the size, shape, and overall footprint of the building
- Orientation: solar passive design principles to make use of the sun’s energy
What were the key challenges?
During the sketch design stage we explored a number of concepts that would meet the client's brief. Once a final sketch design was chosen, we approached a number of builders as we believe early collaboration between all parties with shared values and a common goal is crucial to a successful project. The builder that we decided to work with already a ‘Certified Passivhaus Tradesperson’ with two completed Passivhaus projects, so as we moved into the Design Development & Documentation stages we explored whether this project would be feasible/desirable to meet this standard and it was agreed to go down this path. (As Passivhaus is so new in Australia, this makes him the most experienced Passivhaus builder in the country).
This challenge here was that a ‘rectangular box house’ can achieve passivhaus criteria much easier than the footprint/shape of the home we’d designed with it’s courtyards - due to the external wall areas. I.e. This meant increased insulation and Triple-Glazed insulated windows from Europe were required. However this proved that this house was still able to meet passivhaus certification criteria - although for an extra cost premium to do so.
Another challenge was from my (the architect’s) perspective was the steep learning curve about building science and Passivhaus construction. I already had a strong understanding of the principles, as I’m passionate about healthy, comfortable and sustainable homes, and I was a member of the Australian Passive House Association. We also engaged an independent ‘Certified Passivhaus Consultant’, to run the data and advise on insulation levels, how to prevent thermal bridging, and to do some hygro-thermal analysis of our wall/roof assemblies to check that condensation was unlikely to occur inside the home, or inside the structure. The builder’s experience and expertise with Passivhaus construction really helped me to put my knowledge into practice. I wanted to learn more about the Building Physics, so I then did the intensive course (& passed the difficult exam!) to become a ‘Certified Passive House Designer’ whilst the project was under construction.
What were the solutions?
Clear and honest communication.
Shared values and a common goal.
Willingness to be open to new ideas from all parties on how to achieve the best possible outcome.
Keen interest to learn more and do high-quality work - be the best you can be. Why settle for anything less.
Key products used:
CONSTRUCTION MATERIALS AND METHODS
CONSTRUCTION: Lightweight construction timber-framed construction for floor/walls/roof
ROOFING: Metal (Colorbond “Wallaby”)
WALLS: Radially-Sawn Timber cladding, Colorbond cladding and Rendered Magnesium Oxide cladding to enclose sub-floor, plasterboard lining internally
WINDOWS AND DOORS: Triple glazing Passive House Certified Windows, Low-e films, Tilt and Turn, Composite frames (timber inside, aluminium externally)
WINDOWS/DOORS COVERING AND PROTECTION: Adjustable Shading, Blinds, Deciduous tree/vegetation, Drapes/curtains. The northern eaves and protruding vertical 'wing' walls on western ends have been designed to shade from the summer sun.
RECYCLED/REUSED MATERIALS: Rocks/stone, Sleepers, Timber
Under roof: Blanket R1.5
Ceiling: Bulk Insulation batts - glass wool R7.0
Internal walls: Bulk Insulation batts - glass wool R2.5 +
External Walls: Insulated panel system PIR boards 2x50mm R6.7
Sub Floor: Bulk Insulation batts - glass wool R7.0
Recycled/reclaimed timber for deck and pergola
Sustainable sourced, radially-sawn SilverTop Ash cladding and timber battens
Recyclable and durable steel sheeting for cladding and roofing
HEALTHY HOME MATERIALS AND DESIGN ELEMENTS:
Airtight house design
Heat recovery ventilation (HRV/MVHR) Zehnder
Cross flow ventilation with openable windows
Low VOC paints/sealer/varnish, Natural oil sealer/finishes
PASSIVE HOUSE CERTIFICATION (once complete)
· First-Rate/NATHERS 7.4stars
“Solar ready” - designed to go on Garage roof ... owners just waiting until they've lived there to see how big an array they need
All electric home (no gas)
Sanden Eco Hot Water Heat Pump
PASSIVE HEATING COOLING:
Passive solar designed home
ACTIVE HEATING COOLING:
Split system air conditioner
Heat exchange ventilation system (MVHR)
Energy efficiency Solar Passive Design Principles
LED lights throughout
WATER HARVESTING, RECYCLING AND WATER SAVING:
Above ground rainwater storage - water tanks 37,000L
Low flow shower heads
Hot water recirculation