Factors affecting window insulation performance

Factors affecting window insulation performance

Windows plays an important role in ensuring a comfortable indoor environment. In cold climates, windows with poor insulation conditions will cause the temperature of the glass surface to decrease rapidly. In order to compensate for the cold air settlement, cold wind and “cold radiation” generated by the low-temperature window surface, it is necessary to take heating measures near the windows.

Factors affecting window insulation performance

According to the European Energy Standard 10077, the formula for calculating the U value of windows is as follows (all heat losses must be included to avoid overestimating the quality of windows):

The U value of the window is calculated according to the following formula:

Uw = [Ag * Ug + Af * Uf + lg * Ψg (+ linst * Ψinst)] / (Ag + Af)

Factors affecting window insulation performance

Uw: U value of glass Ag: area of glass area

Uf: U value of window frame Af: Projected area of window frame

Ψg: Linear heat transfer coefficient of warm edge (mainly determined by quality of warm edge) Lg: Length of warm edge

Ψinst: additional thermal bridge caused by installing windows in the outer wall Linst: length of the installation edge。

According to above formula,we can see that windows U value is affected by the glass U value,profile U value and the glass edge U value,while the most important part is the areas of each part.For most windows,glass account 80% of the overall windows,so decrease the glass U value plays important role,below chart shows how windows U value is affected by the glass U value.

Factors affecting window insulation performance

When glass U value decrease 0.1W/M2.K,Windows U value will decrease by 0.08W/m2.k.So how to decrease the glass windows is the most important issue when designing a windows.Insulated glass with high performance low-E coating will help decrease glass U value to below 0.7W/M2.K. Morn is your turnkey glass and U value manufacturer and supplier from China,if you want to know the glass price and glass Uvalue,please contatc us for more info.

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