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Window frames - more than just a technical component

Window frames characterise the appearance of a house, but also fulfil important tasks in terms of thermal insulation. However, the prerequisite for this is that they actually close tightly.

As glass is transparent, window frames are the part of the window that catches the eye the most. However, their energy properties are really important - not only because they help to save heating costs, but also because mould formation is often associated with leaky window frames.

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Käuferle - leading German manufacturer of garage doors, enclosures and windows

Value inside.

At our company headquarters in Aichach near Augsburg, we develop and produce garage doors, enclosures and partition wall systems as a family business. We also produce windows and front doors in PVC-U and aluminium. All our products comply with the rules of technology and set design accents. They are also sustainable and well thought-out in terms of craftsmanship so that they protect your assets in the best possible way.

Sustainable craftsmanship

We use high-quality window frames, fittings and glass from suppliers in southern Germany for our windows. This promotes the regional economy and reduces our CO2 footprint. At the same time, the first-class components ensure durable products that also have a lot to offer in terms of sustainability - whether it's insulation values, recycled materials or achieving the passive house standard.

Customised production

All Käuferle windows are customised based on the customer's requirements and the respective installation situation. A wide range of window frame profiles made of PVC-U, recycled PVC-U or aluminium are available to provide optimum solutions in terms of construction and design. These can be used in new buildings as well as in the refurbishment of existing buildings.

More energy efficiency with window frames

Window frames as an essential component for thermal insulation

Windows characterise the appearance of buildings, let daylight into the house and protect interiors from fine dust, pollen, heat, cold and moisture. In addition to the glazing, the window frames also play an important role in energy efficiency. This is because heat loss occurs not only in the glass surface, but also in the frame area. Good thermal insulation of the frame profiles is therefore particularly important for aluminium windows.

Thermal insulation for frame profiles made of different materials

While timber window frames are naturally insulated by the air contained in the wood, the filigree bars and cavities filled with insulating material in the window frame of PVC-U windows ensure a good insulating effect. Aluminium frames require thermal decoupling of the inner and outer frame parts, as metals are generally considered to be excellent heat conductors. Insulation values for window frames are specified with the Uf value in W/(m²K). The lower the value, the better the thermal insulation.

Requirements of the passive house standard for window frames

Windows must fulfil high energy efficiency requirements in order to be certified as passive house windows. In addition to triple glazing, the passive house standard requires highly insulating window frames with low heat loss. The installation situation must also be taken into account. For example, windows must be installed in the insulation level - with thermally optimised wall connections and insulated window frames.

Design and material options for window frames

Wooden window frames - sustainable, but high-maintenance

Precisely because they are made from a natural raw material, wooden window frames are particularly sensitive. When planning with timber windows, constructive timber protection is crucial, which protects the window frames from rainwater, for example by means of roof overhangs, so that chemical wood preservatives can be dispensed with. Depending on the type of wood used, timber window frames can also have natural protection against biological pests and environmental influences.

External cover mouldings as weather protection for window frames

To protect timber window frames from rain and UV light, covers made of aluminium, for example, can be used on the outside. These are also available as an option for PVC-U window frames. They can be painted, powder-coated or anodised in any RAL colour and thus offer countless possibilities for customising the character of house façades.

PVC-U window frames - never have to paint again

Plastic windows are usually made of white PVC. However, they are available in every conceivable colour and can just as easily be black. They are also easy to clean, light-resistant and weatherproof, meaning that - unlike wooden window frames - they do not need to be painted regularly. Should you nevertheless wish to paint white PVC-U window frames black, this is also possible, for example with acrylic paint.

Dimensions and measurements of PVC-U window frames

Thanks to stable and, if necessary, reinforced window frame profiles, many manufacturers can offer large window elements in PVC-U - standard window sizes of 2.50 m in width are easily possible, even without partitions at floor level. Windows with such dimensions usually have greater installation depths, which also achieve optimum thermal insulation up to passive house standard.

Why are there holes in the window frame?

Holes in the upper area of PVC-U window frames (not the sash) serve to equalise pressure and prevent heat build-up and material deformation in strong sunlight. Openings in the lower area of the inner part of the frame are usually drainage slots that ensure that rain, melt and condensation water, which would otherwise contribute to mould formation, is drained away.

The basics of sealing window frames

Why sealing window frames is important

Draughts caused by leaking windows are unpleasant. More important and more serious in winter, however, is that warm air escapes through open joints and cold, moist air enters the room. This increases heating costs, and the cold air can also condense on the window frame and in the window reveal, leading to mould growth.

Recognising leaks in the window frame

Every inspection starts with a visual inspection. Damaged or porous areas are often easy to spot. Less conspicuous leaks can be detected with the candle test. In this test, the flame of a candle guided along the window frame begins to flicker due to the draught. An alternative is the paper test: Windows are very likely to be leaking if a strip of paper clamped between the window sash and frame when the window is open can be easily pulled out again after closing the window.

Subsequent sealing of window frames

Leaking window frames can be subsequently sealed - even partially - both in the area of the window sash and at the wall connection. Materials that can be used include self-adhesive foam sealing tape, rubber seals or silicone. Before applying new seals, old sealant residue must always be removed and the relevant areas must be kept free of grease, clean and dry.

Sealing systems - foam, rubber or silicone

Foam sealing tapes are particularly suitable for wooden window frames without circumferential sealing systems consisting of one or more stop seals. They are not very durable and must therefore be replaced regularly every few years. Longer-lasting rubber seals are fitted in existing grooves in the rebate area of the window (after removing the old seal). Silicone is usually used in the transition area between the window frame and the wall.

Frequently asked questions about window frames

Here you will find answers to frequently asked questions about window frames:

What materials does Käuferle use for its window frames?

Our range offers windows and front doors made of PVC-U, recycled PVC-U and aluminium profiles.
Does Käuferle offer windows that fulfil the passive house standard?

With the bluEvolution 92 window series, we achieve a UW value of 0.74 W/m²K and thus fulfil the passive house standard. The Greta® window profile system also offers insulation values at passive house level.
What design options are there for PVC-U window frames?

Our window frames are available in numerous colour variants and foils as well as with painted, powder-coated or anodised aluminium covers.
Are Käuferle windows also available with a centre seal?

Yes, our window frames have two or three stop seals, depending on the model.