The concept of thermal insulation of the window refers to the window's ability to reduce the heat flow between the interior and the outside of the building. It is a key feature of windows, having a significant impact on the energy efficiency of the house or building, the comfort of the residents, as well as on the cost of heating and cooling of rooms. The U-value is a measure that determines how much heat passes through the window. The lower the U value, the better the thermal insulation of the window. Modern windows often use double or triple glazing with a gas layer (e.g. argon) closed between windows, which significantly improves insulation.
