Describes the effectiveness of a joint in the window and indicates how many cubic meter (m3) per hour (h) per joint meter (m) at 1 Pascal pressure difference leach through the window. Assuming an air temperature of 0 ° C and a normal pressure of 1013 mbar (millibars). The smaller the a value, the less air escapes through the joints.



The total energy transmitted expressed as a percentage, and describes the radiation passing through a material in the wavelength range of 300-2500 nm (nanometers). This value is relevant i.d.R. only for glass, because it is used to calculate the solar energy gain needed. The larger the value, the more energy can pass through the window into the interior, thus contributing to warming. For example sunglass lenses have a low g-value.



This value describes the annual energy requirements, depending on the external surface area (m2) - for the household heating requirements and the primary energy demands (heating, hot water, household electricity, etc.), when in normal use.


n50 Value

Describes the air tightness of a building - it provides information about the quality of the so-called air-tightness level. Substituting the measured air flow in one hour in relation to the heated building volume, we get the n50 value. It indicates how many times the entire volume of air of a house at 50 Pascals (Pa) pressure difference is exchanged per hour.

In passive houses, the n50-value should be below 0.6, meaning the escape of air should be at most 60% by volume in any hour. In cmparison older houses which ahve not been renovated experience figures in excess of 10.



The exposure to noise is unpleasant and can have an adverse affect on the quality of life. Noise results from air pressure fluctuations that are absorbed by the human ear to the brain.

The soundproofing of the window is measured in decibels (dB). The higher the number, the better the insulation. It indicates how much sound energy from the original sound soure is transmitted. In an insulation of 10 dB, 1/10, at 20 dB 1/100, at 30 dB 1/1000, etc. of the original sound energy. One experiences a halving of the sound intensity by a reduction of 10 dB. The soundproofing of the window depends on the frame material, insulation, sealing of the window and the building joints


Heat transfer coefficient


The U-value indicates how much heat flows (in watts) per square meter per degree Kelvin temperature difference for a component (W/m2K). A low U-value indicates a low heat and energy loss - the component is well insulated.

The heat transfer coefficient is divided into:

Ug value for the thermal insulation glazing

U-value of insulation for the window frame

Uw thermal insulation value for the window - is calculated from all the components of the window - Ug and Uf and Ψ (psi)




Due to the fact that about 25% of the energy can be lost through the windows, the thermal insulation of the window is particularly important. The energy transport by the window is not just heat loss - due to the transparency of the glass but also an energy gain achieved. With careful planning, the arrangement of windows (large windows facing south) will improve the energy balance of the building and heating costs are then reduced accordingly.


The thermal insulation of a window depends on the frame material, insulation and the fit of the window. The parameter for the insulation properties of the window is the U-value. The smaller the number, the better the insulation. It is possible to improve the U-value with optional features such as window blinds and shutters.


A house can loose about 25% of the energy throughits windows.  With the energy savings and passive house windows supplied by Internorm you can reduce the loss significantly.


The innovative passive house windows from Internorm control the main factors influencing thermal comfort .






The heat transfer coefficient for heat transfer in the vicinity of the edge seal of the insulating glass. Measured in W / mK, the lower the thermal conductivity, the better the insulating properties.

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