Wärmedurchlasswert

The Wärmedurchlasswert, often abbreviated as WDW, is a German term used in building physics. It describes the heat flow rate through a specific area of a building component under a defined temperature difference. Essentially, it quantifies how much heat passes through a material or construction element, such as a wall or window, per unit of time and per degree of temperature difference between the inside and outside.

The unit for Wärmedurchlasswert is Watts per square meter Kelvin (W/(m²·K)). A lower Wärmedurchlasswert indicates better thermal insulation, meaning less heat is lost from the building in colder weather and less heat enters in warmer weather. Conversely, a higher Wärmedurchlasswert signifies poorer insulation. This value is crucial for assessing the energy efficiency of buildings and for calculating heating and cooling loads. It is closely related to the U-value (Wärmedurchgangskoeffizient), which is a more commonly used international standard. The Wärmedurchlasswert specifically refers to the heat transmission through a composite construction, taking into account all layers and their thermal properties.