When it comes to sustainable builds, the Passive House model is a great way to achieve maximum energy efficiency. The concept of a Passive House first emerged 30 years ago in Germany, and the standard means these homes are able to consume up to 90% less energy than the average home.

A Passive House has an airtight building envelope that is very well insulated, helping to regulate the internal temperature without relying on artificial heating or cooling. Instead, these homes are warmed from passive sources such as the sun, the heat emitted by occupants, or warmth given off by household appliances.

According to the Australian Passive House Association, Passive Houses follow five key design principles: airtightness, thermal insulation, mechanical ventilation heat recovery, high performance windows and no thermal bridges.

While more popular in Europe, the Passive House standard is starting to gain more traction in the Australian market. It comes as people are more interested in how to make their new builds as energy efficient as possible while maintaining indoor comfort and wellbeing.

Product manager at green energy company Stiebel Eltron, Steffen Reich, says they have noticed a growing awareness of Passive Houses, particularly amongst second or third home buyers.

“The motivation ranges from doing the right thing for the environment to saving significantly on heating and cooling your home,” he says.

Certified Passive House Architect and Director of Sunpath Architecture, Niall O Healaithe, says Passive House living has many advantages.

“Passive Houses are healthier homes, as they are close to airtight and only use filtered air,” he says.

“The air quality inside the home is higher as the mechanical ventilation system eliminates pollutants like traffic fumes, smoke and pollen.”
“Passive Houses maintain very stable and predictable temperatures inside without large fluctuations all year round. Typically, temperatures never get below 18 degrees or above 25 degrees Celsius, and there is no difference in temperatures between rooms”.

According to Healaithe, it’s much easier to go ‘off grid’ with a Passive House, as they don’t have high running costs or energy needs, making them easier to achieve self-sufficiency.

“Solar panels and batteries can be installed so that the home can go off grid and operate as normal, which is attractive with climate change and energy uncertainty,” he says.

“The double and triple-glazed windows make Passive Houses much quieter. The occupants don’t hear the neighbours, noisy animals or traffic noise,” he adds.

Niall works exclusively on Passive House projects and acknowledges that while the homes he designs are constructed to meet all Passive House standards, some clients will opt not to independently certify as it is an additional $3000 to $4000 expense to the home post completion.

Healaithe is currently working on a Passive House project in the Melbourne suburb of Camberwell. The original design was commissioned while he was working at Third Skin Architects and the owners continued with Healaithe when he started his own firm, Sunpath Architecture.

The home is a 230sqm two-storey detached Passive House, on a sloping block in Camberwell, designed for a retired couple. The main kitchen, living and dining areas face north to the garden, with a study and guest room on the ground floor as well as a double garage with storage. It also features a covered alfresco dining area plus a drying deck. Internal ramps join the living area and the garage with an internal lift to the first floor. Upstairs features a master suite plus two additional large double bedrooms, a TV and living room and a common bathroom and ensuite.

When it came to designing the roof for this Passive House project, Niall chose to work with Australian manufacturer Bondor for their SolarSpan product. SolarSpan is a long span residential insulated roof panel system that combines Colorbond steel roofing, Expanded Polystyrene with Fire Retardant insulation and a pre-painted ceiling in one. Healaithe says SolarSpan was selected for several reasons.

“The owners wanted to achieve a sleek roofline with classic overhanging eaves and being a long span roofing system SolarSpan allowed the creation of free-floating eaves without additional structure required”.

“SolarSpan was able to provide a lot of insulation in a very thin roof profile, achieving a R5.15 value over conventional roofing systems with R values of 4”.

Healaithe says a bonus was that the lightweight panels were very easy to install within a few hours of being delivered on site. Once the crane had lifted the panels, two people could easily manoeuvre them and fix them into position without the need for additional steel and beams, additional flashings, cladding and fascia boards.

“In one operation with Solarspan we provide the combined structure, roof and insulation and it is instantly weathertight and ready for airtight sealing,” he says.

The insulation the SolarSpan panels provide is complete, in that there are no gaps between joists, providing a fully insulated roof surface and taping the joint underneath, with no ceiling required. It is also a hard wearing and low maintenance product featuring Colorbond steel.

AnchorLight coloured roofing materials absorb less solar radiation, keeping cooler in hotter months than darker coloured roofing material. SolarSpan offers a selection of light colours to ensure that the high performing expanded polystyrene core provides efficient, long-lasting insulation and comfort.

“When used in combination with Passive House design, SolarSpan is a highly energy efficient and durable addition to achieving Passive House design principles and performance criteria,” Healaithe says.

Another incredibly important element of Passive House design is eliminating any thermal bridges to reduce the building’s energy footprint. Rigid XPS board, such as Styroboard XPS by Foamex is one such product that provides continuous insulation for the home’s exterior and under slab.

“Styroboard XPS is made from extruded polystyrene which has incredible air resilience, and is virtually impervious to water, so it doesn’t seal in water that can occur through condensation,” Justin Kelsey, General Manager of The Foamex Group says.

“Materials used to create a thermal barrier that don’t have these inherent product features can lead to issues with mould, mildew and rotting wood down the track,” he said.

Another key design principle for Passive Houses is airtightness. Creating an air-tight building means there are absolutely no gaps in the exterior shell of the building.

“One of the most important areas to insulate during construction is the perimeter slab edge of a building,” Kelsey says.

“Slab edge can be responsible for approximately 80% of the slab’s total heat loss. When there is no insulation on the perimeter foundations, most of the heat is conducted along the slab and out through the exterior face of the footing. Insulating slab edges is paramount to the design of a building trying to achieve passive credentials”.

Justin said Styroboard XPS from Foamex is an ideal material for slab edge insulation.

“Extruded polystyrene (XPS) is a rigid insulation that is formed with polystyrene polymer but manufactured using an extrusion process. This rigid foam provides a strong, yet lightweight and flexible insulation solution which is resistant to water absorption, making it a long term, sustainable solution to reducing slab edge heat loss,” he says.

When they launched into the Australian market, MAXRaft used Styroboard XPS and Styroboard EPS to achieve their first Australian Passive House project, the Leongatha CLT House among the vineyards of Gippsland, Victoria, designed and built by Aphi Projects.The thermal efficient design of the home utilised the insulation qualities of Foamex’s Styroboard XPS and Styroboard XPS products.

Another very important principle of Passive House design is choosing the most energy efficient doors and windows which will allow the sun to warm the interior in winter and minimise it in warmer months. The windows generally need to be airtight and double or triple glazed.

According to Andre Griffs, Head of Design and Architectural Sales at BINQ, timber doors and windows are a great choice for Passive Houses because they can achieve high energy efficiency while also looking fantastic. Griffs noted, however, that since air leakage is a major factor in Passive House efficiency, not only is the material important, but the design and manufacture of the doors and windows is also critical.

“BINQ’s Archetto range of doors and windows have been formally tested by a NATA approved test lab and have achieved results that exceed the Passive House requirements,” he says.

BINQ has been collaborating with one of Melbourne’s leading Passive House builders, G-LUX Builders, on a project known as the Panel House in Warrandyte. When complete, the project will be a certified Passive House.

The Panel House has BINQ triple glazed blackbutt windows installed as they meet the PH standards for their Passive House while also being suitable for the site’s bushfire rating BAL29.

Mass timber glulam panels were used for the floor structure to enable long structural spans and limit the amount of steel in the structure.

Meanwhile, Structurally Insulated Panels were used for the wall and roof structure. These panels are great for speed, insulation and airtightness. The home has a 20kw Solar PV system which will be set up for battery connection.

The owners chose to use Envirocrete from Boral, an environmentally friendly concrete mix that uses 40% less Portland cement and recycled water and sand. They also chose wood fibre insulation which is the highest performing insulation available as well as 30,000 litre rainwater tanks under the house and a highly efficient heat pump hot water system.

A Zehnder Q350 Heat Recovery Ventilation System will provide filtered fresh air while the Zypho drain water will provide the heat recovery, reducing the energy demand required to heat the water for showers.

The home will be complete with a green roof and wall and a freshwater mineral pool. On top of this, a circadian lighting system will provide automatic lighting that depletes blue light at night, encouraging higher levels of melatonin for bedtime.

Steffen Reich from Stiebel Eltron said mechanical ventilation heat recovery (MVHR) is a game-changer in household energy efficiency.

“Combined with the fabric conscious build and a necessary degree of airtightness, heat recovery ventilation can bring the energy requirements of a home down to near zero,” he says.

“With a high level of airtightness required for Passive House buildings, it becomes critical to introduce fresh air into the building envelope, without vast amounts of energy literally going out of the window in the process”.

MVHR improves indoor air quality without the need to keep the windows or doors open by recovering the warm and cool air that would otherwise have gone to waste. They also clean the air from pollution and help to regulate humidity.

Steffen said other prominent elements in Passive House builds are solar PV systems and energy-efficient heat pumps for hot water.

One of Stiebel Eltron’s recent Passive House Certified builds was, in fact, the first large scale building in the southern hemisphere to achieve passive house certification at Monash University in the form of a new student residence.

The main objectives of the project were comfort, health and extremely low energy consumption. The 150 individual rooms were designed to be sustainable and environmentally friendly. An important aspect was that the whole construct was powered by renewable energy. This is where Stiebel Eltron came into play.
The complex is fully electric, supplied with wind energy by the wind farm, Murra Warra, and draws solar energy from the 60kWp rooftop solar panels. As part of the all-electric-strategy, Stiebel Eltron supplied and commissioned three WPL23E three phase air sourced hydronic heat pumps for hot water.

When it comes to sustainability in building, the Passive House model is one of the most energy efficient models around. Passive House builds do require thorough planning and consideration from start to finish, but the end result is a super sustainable home, free from noise and air pollution that is very comfortable to live in year-round without any artificial heating.

Suppliers

Stiebel Eltron: Stiebel Eltron Australia | Architecture & Design (architectureanddesign.com.au)

Bondor: Bondor® | Architecture & Design (architectureanddesign.com.au)

BINQ: BINQ | Architecture & Design (architectureanddesign.com.au)

Foamex: The Foamex Group | Architecture & Design (architectureanddesign.com.au)

Image: https://sustainablehouseday.com/listing/thornleigh-passive-house/

Nathalie Craig

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