Paul McAlister Architects - The Barn Studio, Portadown, Northern Ireland, Bespoke Houses, House Extensions, Housing Developments, Northern Ireland, Architects, Portadown, Armagh, Craigavon Lurgan, Chartered Architects

What is a Passive House?

The term PassivHaus refers to a voluntary, low energy construction standard, first developed over a decade ago by Dr Wolfgang Feist of the PassivHaus Institut in Darmstadt, Germany. Buildings of this construction standard have been built mainly in Germany but also in Austria, Switzerland, USA and more recently in the UK.

PassivHaus Design Standard
The PassivHaus Institut lays down the standard for PassivHaus construction and, on completion, provides certification for buildings which meet its standard. The technical definition of this standard is very clear and straightforward for climate conditions, between northern hemisphere latitudes 40 degrees (Madrid and Ankara) and 60 degrees (Oslo and Helsinki).

A comfortable internal climate can be maintained without the use of a conventional central heating system or cooling system. The building heats and cools itself and is therefore passive. The cost savings from dispensing with the conventional heating system can be used to fund the upgrading of the building envelope and the heat recovery ventilation system. After the main criteria have been followed, additional energy requirements can be catered for using renewable resources.

PassivHaus Standard
The PassivHaus design standard is integrated with the architectural design and although it has generally been used for new buildings, it has also been used for refurbishment projects. A building can be certified as a PassivHaus when the following criteria are met:

The building must not use more than 15 kwh/m²/year in heating energy
The standard requires very precise levels of insulation for every construction element. Every external surface must have a U-value lower than 0.15 W/m²K and there are tight restrictions on the relative window surface.
The total use of primary energy (e.g. fuels) for all uses combined (heating, hot water and specifically electricity) may not exceed 120 kwh/m²/year.
With the building depressurised to 50 Pa (N/m²) below atmospheric pressure using an approved air leakage testing method, the building must not leak more air than 0.6 times the house volume per hour.

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