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Passive house windows

The window in a passive house plays a prominent role in two ways – firstly, the heat loss despite large glass surfaces can be reduced and secondly, windows increase the possibilities for heat gain through solar irradiation.

Internorm‘s highly thermally insulating energy saving windows fulfil this seemingly contradictory dual capacity exemplary: Triple heat protection glazing achieves Ug values of up to 0.5 W/m2K and g values (overall energy transmission factors) of up to 62 % – depending on coating and gas fillings.

In comparison Ugvalues of conventional windows often lie at around 1.4 W/m2K.

Besides the glazing however you have to consider the insulation of the window frame as well as thermal bridges at the glass edge and in the connecting area window to wall.

Spacers form thermal bridges, they are usually made of aluminium. Especially for use in passive houses particularly well thermally insulating window frames were developed, which also reduce the glass edge losses.

Stainless steel spacers further reduce losses at the glass edge. For passive house certified components thermally optimised systems – like the Internorm ISO spacers – are used. Following the automobile industry all glass panes are glued to improve structural stability.

Essential Principles For Construction Of Passive House Windows:


Passive house – a sustainable invest

A passive house provides consistent, comfortable temperatures in winter, as well as in summer without using conventional heating or air conditioning systems. Using the existing temperature provided through solar irradiation through the windows as well as the heat from appliances and inhabitants is sufficient, the necessary heating energy for a passive house is only 10 % of that needed for a conventional house.

Optimised energy demand

This results in an annual heating demand of not more than 15 kWh/m2a. The overall energy demand including warm water and household electricity for a passive house is less than 120 kWh/m2a. The heating load of a passive house is not more than 10 W/m2, for a room of 30 m2, this results in a heating load

of approximately 300 Watts – just to illustrate: the heating power of a tea candle is 30 Watts already. This means that 10 tea candles are enough to heat 30 m2 in a passive house. These extraordinary savings are rooted in the two basic principles of minimising thermal loss and optimising thermal gain.

Raising comfort

Due to the powerful insulation the heat stays inside the building, all surrounding surfaces are equally warm. For this reason there is no radiation asymmetry (heat radiation) originating from exterior walls in a passive

house, and also the resulting draught phenomena are avoided. The reverse conclusion would be that heat stays outside in the summer to avoid overheating. This means that in a passive house a consistent living climate is retained throughout the whole year – this provides a high degree of comfort for the inhabitants. Passive houses also make use of highly efficient air conditioning systems to prevent mould growth, dust and any resulting allergies.

Reducing Costs and protecting the environment

As the energy demands of a passive house are reduced by up to 90 %, heating costs and therefore CO2 emissions can be reduced drastically – compared

to a conventionally constructed building, on average 4.000 kg of greenhouse relevant carbon monoxide are avoided each year.

This would correspond to driving about 27.000 km with a typical 6 litre car. Therefore constructing energy efficient passive houses supports climate protection

sustainably and saves on limited resources, such as oil or gas.




One of the major characteristics is the active utilisation of existing energy – minimising thermal losses and at the same time optimising thermal gain, these are the basic principles. But merely combining passive house certified

components is not enough to reach a passive house construction standard: The whole thing is more than the sum of its parts – mutual interactions between the distinct components necessitate integral planning to fulfil three basic demands:


The passive house needs an impermeable outside shell and optimised thermal insulation with integrated ventilation in both directions: Fresh air is sucked into the building underground through the ventilation pipe, pre-heated by the earth, and led to the heat recovery system. There the energy of the used air is

passed on to the fresh, filtered, cold air using a heat exchanger. Here the energy stored in used air, which would normally be lost in traditional airing, is utilised. From there, air is led into the living areas and distributed with special

nozzles in order to avoid draughts. The air is sucked out of sanitary areas

and the kitchen, in order to avoid the spread of unpleasant smells throughout the house.




Internorm is number 1 in passive house windows and the only window manufacturer in Europe with nine passive house certified components. That means that nine window and door systems have been certified by the “Passivhausinstitut Dr. Wolfgang Feist”.



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