The objective measure of thermal insulation: the U-value
Heat loss through building parts is expressed by the heat transfer coefficient or U-value. The U-value indicates how much heat escapes to the outside per square metre if the outside temperature is 1°C lower than inside. This loss of heat can be minimised by using thermally insulating steel profile systems. In building parts made up of several components, the U-value can be determined for each individual component as well as for the part as a whole. A letter in subscript after the U denotes the relevant object: For example, a subscript f refers exclusively to the frame whereas a subscript w refers to the window as a whole. Put more simply, the lower the U-value, the greater the thermal insulation.