What is a Passive House?

The Passive House (German: Passivhaus) is a voluntary building standard, that exceeds the present building regulations by far. Build according to this standard the need for heating will be reduced by 90%. Compared to a conventional build, which has an average heating demand of 150kWh/m2a, these homes need only 15kWh/m2a.

– The remaining heating and hot water demand can be covered almost completely by renewable energies.

– Zero Carbon Housing can be achieved by further reducing the electricity demand and using an alternative means of supply.

Raising the comfort factorPassivHuas Plaque

Because of the highly effective insulation the heat stays within the building, and all the surrounding areas are equally warm. Consequently there is no heat-loss through the outside walls of a passive house, nor any resulting draughts. Conversely, the heat in summer stays outside which prevents overheating inside. Because of these factors the room temperature in a passive house remains constant throughout the year, ensuring a high standard of comfort and cosiness for the occupier. In addition, passive houses have super-efficient ventilation systems (MVHR) which prevent a build-up of mould and dust and their resultant allergies.

Specification of a passive house

One of the key features of a passive house is the use of available energy, for example, the basic principles are the minimising of heat loss and maximising of heat gain. To qualify for the passive house building standard, it is not enough merely to put together passive house-appropriate components; the whole is more than the sum of its parts. Because of the interaction of individual components, integrated planning is essential so that the completed building fulfills the following three requirements:

* Heating output < 15 kWh/m²a

* Primary energy (heating/hot water/household appliances) <120


* Pressure test air change n50 < 0,6 h-1, i.e. in a pressure differential of 50 Pascal, the air current must come to less than 60% per hour of the volume of the building.

Passive house windows- a dual function

By using windows with heat-conserving glazing, as installed in passive houses, it is possible to achieve a U-value of 0.58 W/m²K. These windows have two infra-red reflecting coatings and are filled with either krypton or argon gas. This means that the surface temperature of the glass inside the room is comparable with the air temperature of the room itself. The amount of total solar gain with triple glazed windows is around 60%, depending on glazing and gas-filling. Where these window systems are installed in a south-facing position the heat gains even from December to February are higher than the heat losses.

High quality components are a must for achieving the passive house building standard. An objective appraisal of one particular aspect – energy efficiency – is, however, not always possible. Consequently, the introduction of a norm for product comparison is both effective and meaningful.

The independent Passive House Institute in Darmstadt sets guidelines and carries out a standardized evaluation of products according to these requirements. Certificated products have the appellation, “passive house-appropriate components” and this indicates excellent quality in terms of energy-efficiency. The choice of certificated components eases the task of the planner and helps achieve the passive house building standard.

If you are interested in building a passive house, we recommend speaking to the a qualified Passive House certified architect who can assist with the planning, desing, consultation and more.

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