“Would you pay full price for a fridge if the doors didn’t seal? It’d keep your food cool but the pump would be running all the time costing you loads in electricity. Why do Australians put up with leaky houses, the most expensive things they will likely ever buy? Esky without a lid anyone?”
A recent post on the Australian Passive House Association’s (APHA) Facebook page highlights a common energy-loss related issue associated with Australian buildings—air leakage. It also summarises one of the driving forces behind the German-born building performance standard, PassivHaus.
The building envelope of any certified PassivHaus (Passive House in English) is most importantly striving to achieve a completely airtight internal environment; it is a ‘fabric first’ approach.
Under the Passive House accreditation process, the envelope must achieve an extremely low air leakage performance (less than 0.6 air changes per hour at 50 pascals) so that the building’s energy efficiency, comfort and affordability can be best controlled by mainly passive solar and ventilation design. Highly insulated exterior walls, roof, windows and floor slab are paramount, as is the minimisation of thermal bridges between rooms and the exterior.
In order to achieve Passive House accreditation the building must undergo rigorous testing to ensure it has the optimum seal, meets minimal heating and cooling requirements and has a small overall energy use (total annual primary energy demand of less than 120kWh/m2).
Passive House is foremost a performance standard and accreditation is achieved only through a verification process by which the strict construction guidelines set out in The Passive House Planning Package (PHPP) must be followed and a calculation tool utilised.
Key measures used to achieve Passive House performance criteria:
- good levels of insulation with minimal thermal bridge
- passive solar gains and internal heat sources
- triple glazing
- excellent level of airtightness, and
- good indoor air quality, provided by a whole house mechanical ventilation system with highly efficient heat recovery (Building Research Establishment Ltd, 2011).
To date, only one certified Passive House has been constructed in Australasia, and it comes from across the Tasman in the New Zealand town of Glendowie, Auckland. Jessop Architects were responsible for the design of ‘PH1NZ’ and following its completion have estimated that it was 10-20 per cent more expensive than a standard build but will consume up to 75-90 per cent less energy in operation.
Why there aren’t any accredited Passive Houses in Australia isn’t well known although Clare Parry, chair of the APHA believes there are many happily operating Passive Houses in Australia without the official Passivhaus tag. She also believes it’s only a matter of time before one is built and accredited.
Below is Australasia’s only certified Passive House to date, and below that two that are on the cards for Australia. IF WE HAVE MISSED ANY PLEASE LET US KNOW IN THE COMMENTS FIELD:
PH1NZ - AUSTRALASIA’S FIRST CERTIFIED PASSIVE HOUSE – Jessop Architects
At the core of the PH1NZ is its airtight envelope achieved through attention to insulation and membrane detail in the slab, timber framing, roof and most importantly, all the junction points.
From there, the Heat Recovery Ventilation System (HRVS) and passive solar and cross ventilation design elements can more efficiently control the building’s internal temperature range.
While essentially a passively designed house, the materials below function in the ‘fabric first’ approach as is standard with Passive Houses; sealing and insulating the house was the most important factor for Jessop Architects.
The lower level floors of the house are concrete which was poured over 'EXPOL' 100mm thick EPS polystyrene insulation which is laid on top of a continuous layer of polythene. A layer of compacted sand sits below this and on top of a porous hardfill.
- Exterior: Pre-cut and nailed, Laserframe Structural Timber is kiln dried and forms the majority of the wall frames, while concrete filled blocks are used in some structural instances.
- Interior: Gibralter Board ('GIB® Board') plasterboard is used for interior walls and ceilings and cover R4.0 'Pink Batts' fibreglass wool insulation.
The roof of the garage consists of an insulating layer (IKO Enertherm insulation panels) that are laid on top of a Ecoply substrate and beneath the roofing membrane. The roofing membrane consists of a base-sheet layer of Nuraply 3PV-SA which is fixed over the insulation with 'Ikofix' insulation fasteners.
The exterior of the rear section of the house has Ecoply Barrier applied, with the joints between the sheets taped for airtightness.
Shiplap cedar board that has had a Resene stain is fixed in a rainscreen system to timber battens that are attached to the ecoply. This allows a small airflow cavity between cladding and timber frame.
SOLITEX EXTASANA and INTELLO wall wraps, and INTELLO PLUS connection strips from Pro Clima form a vapour check membrane and prevent uncontrolled air infiltration or leakage through the building envelope.
Ecoply Barrier tape protects outside edges of the ply combined with insulation strips, creates a better seal for the envelope and minimises thermal bridging.
The Heat Recovery Ventilation System (HRVS) - the Zehnder 'ComfoAir 350' is manufactured in the Netherlands and provides thermal control and fresh air to interior spaces.
Jessop chose to use double glazed Visolux rather than triple glazed windows (which is the common standard for Passive Houses). Airtightness around the window frames is managed with the application of an expandable foam between the window frame and the opening, and is air-seal taped connecting the exterior 'Ecoply Barrier' to the window frame. Images: Eco Windows New Zealand.
Images: ECO Windows NZ.
Images and more information available on PH1NZ here: