How to install your energy-efficient windows?

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Correct installation of energy-efficient windows
Thanks to energy-efficient windows you can significantly reduce heat loss from the house. However, they must be installed correctly. Only then you can take full advantage of their thermal insulation properties.

In the case of energy-efficient windows, the so-called warm installation is recommended. This is a common name, and because it is sometimes interpreted in different ways, below we explain exactly what it means.

“Warm assembly of windows in the wall” – is more and more often used assembly, which correct name is layered assembly or tight assembly. However, it is commonly used in Poland to call such installation “warm installation”.

“Warm assembly in the thermal insulation zone” – it is an assembly, which should also be performed as tight assembly, with the difference that windows are installed in the wall insulation zone, using special assembly systems.

Unlike foamed windows, which are unfortunately still often used, warm assembly ensures a tight connection of the window with the building wall, thanks to the use of specialised materials. As a result, less air from outside gets into the building, which in turn influences better energy balance and lower heat losses. Lack of draughts by the windows also means higher comfort of use, less risk of dampening of the window frames and development of mould and fungi, and thus – a better and healthier climate at home. On the other hand, in the case of warm installation in the thermal insulation zone, we can additionally talk about minimising linear thermal bridges, i.e. places with poor thermal insulation. This type of assembly must be carried out by qualified assembly teams.

What is a warm installation?

Warm assembly – regardless of whether it is executed in the wall or the thermal insulation – consists of the application of three sealing layers fulfilling strictly specified functions. The internal layer is to prevent the penetration of the water vapour, gathering in the building, to the space between the frame and the wall. It is made of vapour-proof tapes or tapes with variable diffusion resistance. Usually, assembly foam is placed in the middle. Its task is to ensure appropriate thermal and acoustic insulation. From the outside, the window is protected with vapour-permeable tapes or tapes with variable diffusion resistance. They protect against the ingress of rainwater and wind, and at the same time allow water vapour to freely escape to the outside. Warm installation can also be carried out using multifunctional expansion tapes, which perform the tasks of all three layers performed during layered installation.

When it is possible to use a warm assembly

Warm assembly of windows may be performed in virtually all cases, however, it is worth taking care of a proper selection of materials depending on the type of external wall structure in the building.

In two-layer walls with an insulation layer of 15-20 cm, windows are most often installed flush with the external surface of the wall, i.e. they are installed in the wall. However, the insulation layer must overlap the window frame by about 3 cm. In two-layer walls with an insulation layer of more than 20 cm, windows are more and more often installed in the insulation layer, outside the wall. However, it is also worth paying attention to the later installation of external covers, such as roller blinds or façade shutters.

In three-layer walls, on the other hand, windows have to be installed directly into the insulation layer, between the supporting wall and the façade wall – often made of clinker bricks. In passive buildings, installation in the thermal insulation zone is even mandatory. In this case, special installation systems are used to securely install the windows.

To ensure even better thermal insulation and tightness, windows are installed on the so-called warm sill made of extruded polystyrene XPS.

Proper preparation of window openings

With warm installation, especially when installed in masonry, proper preparation of the reveal surface plays an important role. The sealing and expanding tapes used in this technology must be glued to a smooth and clean surface. This will ensure their permanent fastening. Therefore, all irregularities, e.g. in the case of walls made of ceramic hollow bricks, should be carefully levelled beforehand. Materials used for this purpose should be resistant to moisture. Depending on the type of wall, e.g. heat-insulating mortars or polystyrene adhesives may be used. Energy-saving sill underlays are installed using suitable adhesives. They must be precisely levelled and positioned in the right place on the wall because it will not be possible to correct their position once the adhesive has been set.

For the warm assembly to be performed correctly, the size of the ordered windows must be adjusted to the size of the openings. It is best to measure after the openings have been finally prepared, and in the case of balcony and terrace windows – also after the floor levels have been determined and the appropriate window expansions planned. It is necessary to keep the expansion gaps according to the manufacturer’s recommendations. Their width depends on the type of joinery and planned sealing.

Qualified contractors

Performing the warm assembly requires professional knowledge, experience and precision. Incorrect or careless placement of the sealing layers hurts the final effect. That is why the work connected with installing windows should be conducted only by qualified contractors who know the warm assembly techniques and have experience in performing them. Specialised teams also have the appropriate equipment which is necessary for proper installation in the case of windows with larger sizes or located in hard-to-reach places. It is best to commission the installation to specialists who are certified by the manufacturer. This ensures that the woodwork will be installed using appropriate materials and installation accessories, following current regulations and manufacturer’s guidelines.