WHAT IS PASSIVHAUS?

The passive house concept was developed back in Germany in 1991 by a professor Dr Wolfgang Fiest. Born out of a need to build homes that were not only sustainable, but were ultra-low energy, comfortable, affordable and have excellent indoor air quality.

The name comes from the German “PassivHaus”, the literal translation is passive building. Passivhaus is passive only in the sense that the building envelope does most of the work to maintain the comfortable temperature inside the building (without the active input from the occupants).

HOW DOES PASSIVHAUS WORK?

Designed and built in accordance with 5 building-science principles:

The house must be well sealed. The building envelope creates a solid air barrier, so no air leaks in or out giving full control over the internal environment and significantly improving thermal comfort, (windows are still openable though).
Sufficient insulation is required within the building’s envelope, providing enough thermal separation between the heated, or cooled, conditioned inside environment and the outdoors. This improves thermal comfort and reduces the risk of condensation.

An airtight building needs reliable source of fresh air for both human comfort and building longevity. Good ventilation is essential as it prevents accumulation of handful contaminants such CO2, volatile organic compounds (VOCs) and excess moisture which can lead to mould growth. In traditional buildings, fresh air enters the building through a series of vents and through infiltration or draft. This system is uncontrolled and cannot guarantee even ventilation throughout the building. In a Passivhaus mechanical ventilation is combined with heat recovery, known as Mechanical Ventilation Heat Recovery (MVHR). It uses the thermal energy within the building to pre-heat or pre-cool (depending on the season) incoming fresh air, ensuring clean, filtered air is provided regardless of outdoor conditions.

The windows of a Passivhaus must have a good level of insulation. Low emissivity double or triple glazing with thermally broken or non-metal frames must be used. Great windows are crucial, they are the key element in controlling heat flow into and out of the building. They must be appropriately shaded as well.

The insulation not only needs to be sufficient in thickness but also needs to be continuous. This means keeping penetration through the insulation to an absolute minimum, and if unavoidable then using materials that are less conductive to heat (eg. timber instead of metal) and/or incorporating thermal break to avoid thermal bridges.

Thermal bridges are the points at which a conventional house loses energy. They are often unaccounted weak points in the building fabric, resulting in high local discomfort, moisture and mould, while providing a highway for energy loss between the interior and the exterior of the house that.

BENEFITS OF A PASSIVHAUS

Passichaus, Archisoul Architects

An example of a beautifully designed Passive House, by Maxa Design in Victoria

The house works for the inhabitants, hence the term ‘Passive’ and the inhabitants don’t need to do or think about ventilation, heating, cooling and so on.

  • Comfort – The temperature is maintained at a comfortable range (between 20 and 25 degrees).
  • Healthy– The ventilation system must provide 30m3 of fresh, healthy filtered air every hour for every person in the building. The system is able to filter out pollutants, smoke and allergens to create a healthy indoor environment.
  • Economical – Efficient heating systems are used in combination with mechanical ventilation which uses a heat recovery system. In hot weather there is no need for reliance on air-conditioning. When compared to a standard building, there is a reduction of 90 percent energy use for heating and cooling,
  • Sustainable – Ultra-low energy use significantly reduces CO² emissions and provides a positive contribution to mitigating climate change. Each Passivhaus is built to incorporate characteristics that are optimised to the local climate, so the heating and cooling requirements are minimised. A Passivhaus building has structural longevity, due to the ultra-low risks of condensation within the building structure (and interiors).

HOW MUCH DOES A PASSIVHAUS COST?

Passive House projects are high performance and high-quality buildings, where the initial investment costs are typically higher due to the additional design input and superior building components. However, over the building’s life span they are more cost effective than your standard build, due to the low running costs.

The benefits for the inhabitants and for the environment outweigh the initial outlay.

PASSIVHAUS IN AUSTRALIA

Although the concept started in Germany, the uptake in Australia is gaining momentum as an increasing number of astute homeowners see the immediate and long-term benefits.

The Passive House Standard has a general methodology that is used worldwide, whilst each project will have individual components that respond to the local climate.

To ensure that a home is built to this standard an architect qualified in Passivhaus should be engaged at the very start of the project. Here at Archisoul, our senior architect and project leader, Carole Huard is a qualified Passive House Designer and Consultant.

Classification of a Passivhaus:

Certification for building Energy efficiency using time-tested performance and quality metric. It’s the traditional Passive House.

Certification for buildings reducing their primary energy consumption by generating additional energy from renewable energy generation such as photovoltaics. Such buildings produce about as much energy as residents consume.

Certification for buildings that produce more energy than required.

Although Passive House Certification is best suited to new construction, Enerphit is a Certification for existing buildings, recognising that retrofits often cannot achieve the same level of performances as new building can.

Certification that recognises buildings that are close to, but do not fully comply with all Passive House Criteria.

BUSTING THE MYTHS OF PASSIVHAUS

  • Are they ugly? No! Each Passivhaus if designed with a qualified architect can accommodate most design styles. Passivhaus is a standard, not a building design, meaning that owners can choose to build as big or small, simply or extravagantly as they please! A Passivhaus is always designed to individual requirements and is always unique. See the diversity of Passive Houses worldwide.
  • But you can’t open the windows? Yes, you can! To allow in breezes and air and sunshine. But when you want to shut out hot/cold/pollutants/smoke etc, then you can shut the windows and doors and make the home airtight and comfortable. With the constant flow of filtered fresh air, the atmosphere within the home should be fresh and temperate 24/7.
  • But I have an older home. You can quite successfully retrofit older homes. It won’t be quite as successful as a new build Passivhaus, but most homes can be adapted with alterations and additions to increase the levels of comfort.
  • Will I have to use certain building materials that I may not like? Most building materials can be used in a Passivhaus. The preference is for high performance materials, for example, windows should be double/triple glazed and non-metal frames for thermal bridging. Use of materials that are less conductive to heat (eg. timber instead of metal) and/or incorporating thermal break to avoid thermal bridges. At Archisoul we prefer to use materials that are sustainable and have low embodied energy, although currently this is not taken into account in the Passivhaus certification. These types of materials include, hemp, hempcrete, bamboo fibre, hardwood, cork, bioplastic as well as eco-friendly paints and finishes. When choosing a material, we look for different certifications like Global Green Tag, Good Environmental Choice and Green Tick.

Would like to know more?

Carole Huard is our inhouse qualified Passive House Designer and Consultant.
If you would like to learn more about Passivhaus and its sustainability, costs, processes, and what to expect, please contact us on 02 9976 5449.

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