PassivhausA measurable standard applied across different climates

What Passivhaus is

Core principles and measurable performance

Passivhaus, which is German for Passive House, is an international building performance standard developed by the Passive House Institute. It uses detailed modelling, design, construction quality, testing and certification to assess whether a building meets defined performance criteria.

The standard is not an architectural style. Different materials, construction systems and design approaches may be used where the completed building satisfies the applicable criteria.

Core principles

Performance criteria

Passivhaus certification assesses several measurable criteria. These include heating demand or heating load, cooling and dehumidification demand or cooling load, airtightness, renewable primary energy demand and, for some certification classes, renewable energy generation.

The current Passive House Institute criteria include:

• A heating demand of no more than 15 kilowatt hours per square metre each year, or compliance with the alternative heating load criterion
• A cooling and dehumidification demand that includes a climate dependent allowance, or compliance with the applicable alternative cooling criteria
• An airtightness test result of no more than 0.6 air changes per hour at 50 pascals
• Renewable primary energy criteria for the Classic, Plus and Premium certification classes

The applicable criteria should be confirmed against the current Passive House Institute requirements for the project. Buyers do not need to memorise the figures. What matters is whether the building has been independently assessed and certified against the relevant standard.

Certification

Certification involves a detailed review of the design and supporting calculations, together with evidence from construction and commissioning. This may include the Passive House Planning Package assessment, airtightness testing, ventilation commissioning information and other records required by the authorised building certifier.

Ask who certified the building, which standard and certification class apply, and whether the final certificate and supporting documentation are available. A design intention, preliminary assessment or claim that a home uses Passivhaus principles is not the same as completed building certification.

The cost and practical value of pursuing certification vary with the project, design team, builder, site and construction method. Comfort, energy use, indoor conditions, construction quality and the value a buyer places on independent verification may all form part of the decision. Fixed premiums, savings and payback periods should not be assumed.

Passivhaus in Australia

Applying the standard in a warm humid climate

The Passivhaus standard applies internationally, but the design response changes with the climate. In a warm humid location, cooling, dehumidification, shade, solar control, surface temperatures and ventilation strategy may carry greater weight than they would in a cold climate.

The building envelope still manages heat transfer in both directions. The aim is not simply to retain or exclude heat, but to maintain comfortable indoor conditions while meeting the applicable energy criteria.

Subtropical Passivhaus priorities

For a project in Noosa, orientation, external shading, glazing, insulation, airtightness, ventilation, cooling and dehumidification should be modelled together.

An energy recovery ventilator may reduce part of the moisture load associated with outdoor air, but it does not automatically control indoor humidity. Depending on the building and climate data, active cooling or dehumidification may also be required.

The appropriate glazing, insulation and ventilation equipment depend on the modelled performance of the individual building. No one glazing type, solar heat gain coefficient or ventilation system should be treated as universally suitable.

EnerPHit: for existing buildings

EnerPHit is the Passive House Institute's certification standard for retrofits where the full Passivhaus criteria may not be practical because of the constraints of an existing building. It provides a recognised assessment and certification pathway, with requirements that vary according to the project and climate.

For buyers considering a substantial renovation, ask whether EnerPHit certification is actually being pursued and which designer, assessor and building certifier are involved.

Homes using Passivhaus principles

Some homes use selected Passivhaus principles without pursuing certification. These features may still contribute to comfort or building performance, but terms such as Passivhaus inspired or near Passivhaus do not establish that the completed building meets the standard.

Where certification has not been completed, assess the design, systems, construction evidence and testing on their own merits. Selected features should not be treated as providing performance equivalent to a certified building.

Local context

What this means in Noosa

Passivhaus can be applied in Noosa, but the design must respond carefully to the site's climate, orientation, exposure, shade and humidity.

Airtight construction does not mean windows can never be opened. A certified building may include operable windows for natural ventilation when outdoor conditions are suitable, while using controlled ventilation and any required conditioning when the building is closed.

For a new build or major renovation, involve professionals familiar with both the Passivhaus standard and warm humid design from the early planning stages. Certification depends on coordinated design, modelling, construction, testing and commissioning rather than features added near the end of a project.

Buyers should distinguish between a certified building, a project currently pursuing certification and a home that simply refers to Passivhaus ideas in its marketing.

What to verify

Questions for a Passivhaus claim