PVC window Kömmerling 88

In window construction, hardware refers to the components that enable the window to be opened and closed. It therefore comprises the locking mechanism on the opening side of the window sash and the corresponding keeps in the frame, as well as the hinges on the opposite side of the window sash. All of the mechanics that allow a window sash to be opened, and in the case of a tilt-and-turn window to be turned or tilted, are also part of the hardware. In professional terminology, the window handle used to operate the hardware is not counted as part of the hardware itself, but is often also "meant" when hardware is spoken of.

The term spacer refers to the window components that form the transition between the glass surface and the frame profile. They are also responsible for the distance between the individual glass panes of a multiple glazing unit, hence the name. In order to achieve a good U-value and to significantly minimise heat losses at the edge seal, modern spacers are no longer made of aluminium, but of flexible structural foam, composite plastic or plastic-coated stainless steel. These are used when a window is to be produced with what is known as a "warm edge". Passive house standard windows are only possible with such modern spacers.

The centre seal, just like the stop seal, is a type of rebate seal. These seals protect windows and doors against driving rain, noise and wind. The centre seal is fitted to the central rebate of the window profile. This seal is made of an elastic, durable rubber and reliably closes all the gaps between the window or door frame and the sash or leaf. The centre seal's special water-collection chamber ensures that any water that has penetrated or condensed is collected and channelled to the outside. The rebate seal plays an important role in optimising the window's U-value and improves noise protection. The centre seal of windows and doors, in particular, fulfils the function of keeping potential burglars out.

Modern windows and doors are constructed to keep the greater part of street noise outside. The sound insulation values (the sound reduction index) indicate how effectively the sound damping of a building component works.

The standard DIN 4109 "Sound insulation in building construction" sets out the requirements for sound insulation and defines the sound insulation classes. The sound insulation value is given in decibels (dB).

Example: the sound insulation value, or sound reduction index, of a window with insulating glazing is 32 dB Rw,P (or Rw p). The designation Rw denotes the reference value and P stands for the test value (tested in the laboratory). The sound reduction index of 32 dB Rw,P indicates that, in the laboratory measurements, the tested building component reduced the noise level by 32 dB.

In construction, the rule applies that the test value of a building component (Rw,P) should be 5 dB higher than the actual value (Rw). On average, a modern window with standard insulating glazing lets through only about 10% of the noise.

Sound insulation classes and the associated sound reduction index:

• Class 1 25-29 dB
• Class 2 30-34 dB
• Class 3 35-39 dB
• Class 4 40-44 dB
• Class 5 45-49 dB
• Class 6 over 50 dB

For living and working spaces, sound insulation class 1 is the standard; for schools, classes 2 and 3; for hospitals, 3 and 4.

Windows, glass walls and doors should also be able to withstand strong wind. The higher up in a building the corresponding component is installed, the greater the wind load. The wind load to which a building or its components are exposed also depends on the location of the building itself.

Wind load resistance is classified in accordance with the DIN EN 12210 standard: from Class 0 (not tested) to Class 5 (high resistance). In addition, three classes (A, B, C) are distinguished according to the relative frontal deflection under wind load. The final classification of components with regard to their wind load resistance is expressed using a letter-number combination, where the letter indicates the class of relative frontal deflection and the number indicates the wind load class.

The SWISSPACER warm edge spacer has become a byword for the effective prevention of thermal bridges on windows. It provides a special insulating effect at the edge of the insulating glass unit and determines the spacing between the panes. This prevents heat from escaping to the outside via the edge of the glass in winter and reduces the formation of condensation.

Windows have to meet ever more requirements, and development has advanced considerably over recent decades, particularly in the field of thermal insulation. Multi-pane insulating glass is one example of this. However, it can only deliver its full efficiency when a warm edge is built into the window by means of spacers. Triple glazing in particular benefits from an effective edge seal, which reduces energy loss to a minimum and supports the window's thermal insulation.

The thermal transmittance coefficient, abbreviated U for unit of heat transfer (the unit of heat transfer), replaced the k-value in the course of European standardisation. Measuring the U-value determines the heat loss from the inside to the outside, specifically per square metre and per hour at a 1° temperature difference.

A window's thermal insulation depends on the frame material, the glazing and its airtightness. A window's insulating properties are determined by the U-value. The lower this figure, the better the thermal insulation.

For windows, three U-values are generally distinguished. The thermal transmittance coefficient Uw refers to the entire window. This value incorporates the U-values for the glazing Ug and the frame Uf.

• Uf = U frame – is the U-value of the window frame.
  The Uf-value is determined by measurement for the frame-and-sash combination. The visible width of the profile is taken as the area for calculating the Uw-value.

• Ug = U glazing – is the U-value of the glazing.
  The Ug-value depends on the type of gas filling in the cavity between the panes, the distance between the panes and the number of panes.

• Uw = U window – is the U-value of the entire window.

The thermal transmittance coefficient for windows is generally calculated for the standard window size of 1.23 m x 1.48 m. Please note that larger glass areas achieve better values, since glazing allows better U-values than the frame material.

Under OIB Guideline 6 of 2011, the Uw-value for standard glazing must not exceed 1.4 W/m2K. The German Energy Saving Ordinance (EnEV) of 2014 limits the thermal transmittance coefficient to 1.3 W/m2K for an existing building. Windows with a Uw-value no greater than 0.8 W/m2K are considered suitable for passive houses.