The Passive houses They are modern, the subject of publications and boards, and the subject of numerous architectural projects. Nobody questions its energy efficiency and we all probably know how many windows have to do with it. But what exactly are the properties of a window to use when building a passive house?
What is a passive house or a passive house?
In general, the passive house is defined as a residential building with very low energy consumption. The design of the passive house is based on very demanding technical and creative criteria that enable maximum use – absorption and storage – of energy and natural light in winter and a minimization of solar frequency in summer. These are buildings with excellent thermal insulation and strict penetration control. Heating a passive house does not consume more than 1.5 liters of diesel or 1.5 m3 of natural gas (equivalent to 15 kWh) per square meter and year. For this reason, it is believed that a Passive house reduces energy consumption by 60 to 80% (depending on the weather). In addition, thanks to mechanical ventilation systems with heat recovery – which are constantly active – they guarantee very good air quality in the house, even without the windows having to be opened. That is why passive houses should be energy-efficient, but also durable, healthy and comfortable.
One of the main requirements for a passive house is the highly efficient thermal insulation of all its elements (walls, doors and windows). Windows play a special role as they are the weakest structural element in terms of energy.
Windows for passive houses
The passive house standard defines a number of very strict criteria for windows. The windows of passive houses must have the following properties:
- The total heat transfer coefficient must be equal to or less than 0.8 W / m2K. (Uw ≤ 0.8 W / m 2 K),
- The heat transfer coefficient of a wall window must be equal to or less than 0.85 W / m2K. (Uw ≤ 0.85 W / m 2 K),
- the solar factor « g » must be greater than 50%.
Now you can buy windows on the market with Uw values up to 0.66 W / m2K and PVC windows the IGLO ENERGY series enables a further reduction to 0.6 W / m2K.
Passive window components
In order to produce a window with good insulating properties, all elements are important. However, the following components must not be missing in the passive window:
- The glazing must consist of at least two panes (three panes can be the optimal version).
- The glass must be adapted to the climatic zone and the geographical orientation of the window. Basically, they should capture the warmth of the house in winter and keep it outside in summer,
- The partitions between the shutters are of particular importance. Aluminum or stainless steel dividers are commonly used in traditional windows, but the degree of heat transfer from both materials is very high. In addition, an undesirable thermal bridge is created. Passive windows must therefore have high-quality heat separators such as SWISSPACER Ultimate.
- The air chamber should be filled with a noble gas that reduces the heat permeability more than ordinary air.
- The PVC profiles used must also be very insulating. Pay attention to the number of cameras in the profile (at least 5) and their width. It is also important that the seal between the frame and the glazing is done very well.
- Finally, the passive window must be properly installed in the house wall. This includes both the sealing between the frame and the facade and the preselection of the installation location. Passive houses generally avoid glazed rooms in the north walls and prefer south facades, although it all depends on the energy balance that the building architect wants to achieve.
The market for PVC windows offers many good quality products. However, not all effective windows are passive at the same time. To ensure that the window we want to buy meets the strict Passive House standard, ask the seller for a certificate from an accredited laboratory. Every passive window should have one, not just the profile.