The K value of aluminum alloy door and window refers to the insulation coefficient. It is the heat insulation ability of aluminum alloy doors and windows. If the K value is lower, the heat insulation ability is higher, and the insulation performance is also stronger.

The heat insulation ability is the important condition of the thermal insulation properties of door and window. It depends on the glass of door and window. Mostly aluminum door and window all adopt the single or double glass, which double glass is improved based on a single one. The heat insulation ability of double glass has an essential leap compared with the single one. The surface heat transfer coefficient of inside and outside depends on the glass selection in aluminum alloy doors and windows.In the current domestic market, heat transfer coefficient of regular glass has a certain protection.

Whether it is steel or aluminum profiles,the heat insulation coefficient is much lower than the glass. So the traditional aluminum door and window always pay attention to reduce the profile’s area to cut down the K value. And the recent new bridge aluminum profiles and multi-cavity aluminum, their thermal resistances are much higher than the glass as main material in aluminum window and door frame. This breaks the bottleneck of aluminum alloy doors and windows in k value.