In terms of sustainable buildings, the passive house model is a good way to achieve maximum energy efficiency. The concept of passive houses first appeared in Germany 30 years ago. This standard means that the energy consumption of these houses can be reduced by up to 90% compared with ordinary houses.

The Passive House has a sealed building envelope with good heat insulation and helps to regulate the internal temperature without relying on manual heating or cooling. Instead, these houses are heated from passive sources, such as the sun, the heat emitted by the occupants, or the heat emitted by household appliances.

According to the Australian Passive House Association, passive houses follow five key design principles: air tightness, thermal insulation, mechanical ventilation and heat recovery, high-performance windows and no thermal bridges.

Although more popular in Europe, passive house standards are beginning to gain more appeal in the Australian market. This is because people are more interested in new buildings that improve energy efficiency as much as possible while maintaining indoor comfort and well-being.

Steffen Reich, product manager of the green energy company Stiebel Eltron, said that they have noticed a growing awareness of passive houses, especially among second or third home buyers.

"Motivations range from doing the right thing for the environment to significantly saving home heating and cooling costs," he said.

Niall O Healaithe, Certified Passive House Architect and Director of Sunpath Architecture, says that living in a passive house has many advantages.

"Passive houses are healthier houses because they are almost airtight and only use filtered air," he said.

“Because the mechanical ventilation system eliminates pollutants such as traffic smoke, smog, and pollen, the air quality in the home is higher.” “The internal temperature of passive houses remains very stable and predictable, with no major fluctuations throughout the year. Normally, The temperature is never lower than 18 degrees Celsius or higher than 25 degrees Celsius, and there is no difference in temperature between rooms."

According to Healaithe, passive houses are much easier to "off-grid" because they do not have high operating costs or energy requirements and are easier to achieve self-sufficiency.

"Solar panels and batteries can be installed so that homes can be disconnected from the grid and operate normally, which is attractive in the face of climate change and energy uncertainty," he said.

"Double and triple glazing make passive houses quieter. Residents cannot hear neighbors, noisy animals or traffic noise," he added.

Niall specializes in passive house projects and admits that although the construction of the house he designed meets all passive house standards, some customers will choose not to conduct independent certification because it will increase the cost of 3,000 to 4,000 US dollars after the house is completed. 

Healaithe is currently working on a passive house project in Camberwell, a suburb of Melbourne. The original design was commissioned when he was working at Third Skin Architects, and when he founded his own company, Sunpath Architecture, the owner continued to collaborate with Healaithe.

The house is a 230-square-meter two-story passive house, located in a sloping block in Camberwell, designed for a retired couple. The main kitchen, living area and dining area face north to the garden. There is a study room and guest room on the first floor, as well as a double garage with storage room. It also has a covered open-air dining area and a drying platform. An internal ramp connects the living area and garage with an internal elevator, leading to the first floor. Upstairs there is a master bedroom suite and two other large double bedrooms, a TV and a living room, as well as a public bathroom and an ensuite bathroom.

When designing the roof for this passive house project, Niall chose to work with Australian manufacturer Bondor to develop their SolarSpan product. SolarSpan is a large-span residential thermal insulation roof panel system that combines a Colorbond steel roof, expanded polystyrene, fireproof insulation and pre-coated ceilings into one. Healaithe said that SolarSpan was selected for several reasons.

"The owner wanted to obtain a smooth roof line with classic overhanging eaves, and as a large-span roof system, SolarSpan allowed the creation of free-floating eaves without the need for additional structures."

"SolarSpan is able to provide a lot of insulation in a very thin roof profile, which has an R5.15 value compared to a traditional roof system with an R value of 4."

Healaithe said one benefit is that the lightweight panels are very easy to install within a few hours after delivery to the site. Once the crane lifts the panels, two people can easily manipulate them and fix them in place without the need for additional steel and beams, additional waterproofing, cladding and dashboards.

"In an operation with Solarspan, we provided a combined structure, roof and insulation material, which can be immediately weathertight and ready for airtight sealing," he said.

The insulation provided by SolarSpan panels is complete because there are no gaps between the joists, providing a fully insulated roof surface and pasting joints underneath, without the need for a ceiling. It is also a wear-resistant and low-maintenance product, using Colorbond steel.

AnchorLight colorful roofing material absorbs less solar radiation, and it stays cooler in hot months compared to dark roofing material. SolarSpan offers a variety of light color options to ensure that the high-performance expanded polystyrene core material provides efficient, long-lasting insulation and comfort.

"When used in conjunction with Passive House design, SolarSpan is an energy-efficient and durable complement that achieves Passive House design principles and performance standards," Healaithe said.

Another very important element of Passive House design is the elimination of any thermal bridges to reduce the energy footprint of the building. Rigid XPS boards, such as Foamex's Styroboard XPS, are such a product that provide continuous insulation for the exterior and floor of the house.

"Styroboard XPS is made of extruded polystyrene. It has incredible air resilience and is almost impervious to water, so it will not be sealed in water that may occur due to condensation," said Justin Kelsey, General Manager of Foamex Group .

“The materials used to make the insulation layer do not have these inherent product characteristics, which may cause problems such as molds, mold, and wood rot,” he said.

Another key design principle of the Passive House is air tightness. Creating an airtight building means that there are absolutely no gaps in the shell of the building.

“One of the most important thermal insulation areas during construction is the edge of the surrounding slabs of the building,” Kelsey said.

“The edge of the slab accounts for about 80% of the total heat loss of the slab. When there is no insulation layer on the perimeter foundation, most of the heat will be conducted along the floor and out through the outer surface of the foundation. The design of certified buildings is crucial."

Justin said Foamex's Styroboard XPS is an ideal board edge insulation material.

"Extruded polystyrene (XPS) is a rigid insulating material made of polystyrene polymer but manufactured using an extrusion process. This rigid foam provides a strong, lightweight and flexible thermal insulation solution The solution, which is resistant to water absorption, makes it a long-term sustainable solution to reduce heat loss at the edge of the board," he said. 

When they entered the Australian market, MAXRaft used Styroboard XPS and Styroboard EPS to realize their first passive house project in Australia, the Leongatha CLT house in Gippsland Vineyards in Victoria, designed and built by Aphi Projects. The thermal efficiency design of the house utilizes the insulation properties of Foamex's Styroboard XPS and Styroboard XPS products.

Another very important principle of passive house design is to choose the most energy-efficient doors and windows, so that sunlight can warm the room in winter and minimize it in warm months. Windows usually require airtight and double or triple glazing. 

Andre Griffs, head of design and construction sales at BINQ, said that wooden doors and windows are an excellent choice for passive houses because they can achieve high energy efficiency and look great at the same time. However, Greaves pointed out that because air leakage is a major factor in the efficiency of a passive house, not only materials are important, but the design and manufacturing of doors and windows are also critical.

"BINQ's Archetto series doors and windows have been formally tested by a testing laboratory accredited by NATA, and have achieved results that exceed the requirements of the Passive House," he said.

BINQ has been cooperating with G-LUX Builders, one of Melbourne's leading passive house builders, to jointly develop a Panel House project called Warrandyte. Upon completion, the project will become a certified Passive House.

The panel house is equipped with BINQ triple-glazed blackbutt windows because they meet the PH standard of the passive house and are also suitable for the bush fire class BAL29 on site.

A large amount of wood plywood is used in the floor structure to achieve a longer structural span and limit the amount of steel in the structure.

At the same time, structural insulation panels are used for wall and roof structures. These panels are very suitable for speed, insulation and air tightness. There is a 20kw solar photovoltaic system at home, which will be set up as battery connection.

The owner chose to use Envirocrete from Boral, which is an environmentally friendly concrete mixture that uses 40% less Portland cement and recycled water and sand. They also chose wood fiber insulation material, which is currently the highest performance insulation material, as well as a 30,000-liter rainwater tank and an efficient heat pump hot water system under the house.

The Zehnder Q350 heat recovery ventilation system will provide filtered fresh air, while the Zypho drainage will provide heat recovery, thereby reducing the energy requirement for heating the shower water.

The residence will be equipped with green roofs and walls, as well as freshwater mineral pools. Most importantly, the circadian lighting system will provide automatic lighting, consume blue light at night, and promote melatonin levels before going to bed.

Steffen Reich of Stiebel Eltron says that mechanical ventilation heat recovery (MVHR) is a game changer for household energy efficiency. 

"Combined with the focus on fabric construction and the necessary air tightness, heat recovery ventilation can reduce the energy demand of the home to nearly zero," he said.

 "Because passive house construction requires a high degree of airtightness, it has become very important to introduce fresh air into the building envelope. During this process, there will not be a lot of energy flowing out of the windows."

MVHR improves indoor air quality by recycling the warm and cold air that would otherwise be wasted without opening doors and windows. They can also purify pollution in the air and help regulate humidity.

Steffen said that other prominent elements in passive house construction are solar photovoltaic systems and energy-efficient hot water heat pumps.

In fact, one of Stiebel Eltron's recent Passive House certification is the first large building in the Southern Hemisphere to obtain Passive House certification at Monash University in the form of a new student dormitory.

The main goals of the project are comfort, health and extremely low energy consumption. The design of 150 individual rooms is sustainable and environmentally friendly. An important aspect is that the entire building is powered by renewable energy. This is where Stiebel Eltron comes into play. The complex is fully electric, with wind energy provided by the wind farm Murra Warra, and solar energy is obtained from 60kWp rooftop solar panels. As part of the all-electric strategy, Stiebel Eltron supplied and commissioned three WPL23E three-phase air source hot water circulation heat pumps.

When it comes to building sustainability, the passive house model is one of the most energy-efficient models. The construction of a passive house does require thorough planning and consideration from start to finish, but the end result is a super sustainable house, free of noise and air pollution, and very comfortable to live throughout the year without any artificial heating.

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

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

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

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

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

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