U-value
The U-value is an important term when selecting loft ladders and flat roof exits. It provides information about the insulating performance of a material. Therefore, it is also called thermal insulation value or heat transfer coefficient.
The U-value describes the amount of energy or heat that flows through a material when there are different temperatures on both sides of the material. The unit of the U-value is W/m2K (watts per square metre and kelvin). The lower the U-value, the more the material insulates.