The window in a passive house plays an excellent role in two ways: firstly, the heat loss can be reduced despite large glass areas, and secondly, windows open up possibilities for heat gain through solar irradiation.
Highly thermally insulating Internorm windows fulfil this double role exemplary which first appears contradictory. Ug values as low as 0.4 W/(m2K) can be achieved with thermal insulation glazing which is used in passive houses.
Windows in passive houses are tripled glazed and frames are also very well insulated in order to fulfil the high requirements on thermal insulation. As 30 to 40% of the window opening consists of the frame, the quality of the frame is paramount.
In detail, passive house windows offer you the following advantages:
Passive house (or PassivHaus) is a building standard which requires buildings to use very little energy for heating and cooling. Typically, a Passive House uses just 10% of the energy used by an ordinary house. A Passive House is so well insulated and has so little heat-loss than often the heat produced by the occupants, electrical appliances and sunlight can build up enough to keep the building warm. Sophisticated heat-transfer ventilation systems are used to provide fresh air and prevent condensation without losing heat.
Positioning and orientation of passive house windows needs careful planning to guarantee the necessary solar gain. Windows in winter, therefore, let more solar energy into the building than give off warmth to the outside. Larger glazing areas should ideally be positioned south-facing. As the sun stands higher in the sky in summer, less sunlight reaches the interior of the building and the majority of it is reflected. Therefore, solar irradiation on south-facing windows is reduced in summer and normally no extra sun protection is necessary. East or west orientation because of the low position of early morning and late evening sun in summer can easier lead to overheating and possibly requires relevant sun protection.
As a 'rule of thumb' you can estimate that an east or west facing window receives 60 % and a north facing window 40 % of the useable solar irradiation to that of a south facing window. Passive houses should keep to a max. deviation from south facing by 10°.
Always remember to observe local positions of the sun throughout the whole year and include this in the planning. Also local circumstances such as shading through other buildings or trees can have an influence.
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