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Definition of heat transfer coefficient of uPVC doors and windows

UPVC Windows

The K value is a physical quantity that measures the thermal insulation performance of a material, that is, the heat transfer coefficient.

The K value of architectural glass is defined as: under standard conditions, the heat transfer from one side of the unit area of the glass component to the other side of the air per unit time. The K value is mainly used to measure the heat transfer through the glass system. This value is a function of temperature. The calculation method is the heat passing through one square meter of glass per hour at a temperature difference of one degree Celsius. The unit system is w/m2.k, where w is the heating power, m2 is the glass area, and k is the temperature in Celsius.

The higher the K value, the better the heat transfer performance, but the worse the heat preservation performance.

The meaning of common letter codes:

      Uw — heat transfer coefficient of the whole uPVC window (W/m2•K);

      Ug — the heat transfer coefficient of glass (W/m2•K);

      Ag — the area of the glass m2;

      Uf — the heat transfer coefficient of the profile (W/m2•K);

      Af — the area of the profile m2;

      Lg — the perimeter of the glass m;


Lumei 70 series uPVC Window related technical parameters:


      1. Uf =1.0 W/m2•K

      2. Windowing parameters


uPVC window

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