Materials used in door and window design have a significant impact on energy performance as well as the environmental sustainability of the building. Metsä Wood ThermoWood® is a thermal modified wood. This process has a permanent effect on the wood’s properties providing excellent durability, dimensional stability, thermal insulating qualities and a dark brown colour throughout the wood. Metsä Wood ThermoWood® is an ideal material for window and door frames that are exposed to harsh weather conditions. ThermoWood’s properties are similar to many tropical hardwoods, but not only offers a significantly better alternative with regard to sustainability to endangered tropical species but provides superior U-values.