From the outside, efficient thermal insulation of aluminium windows is barely visible. Nevertheless it is a key factor when it comes to having a comfortable and energy-saving living environment. In order to reduce the thermal transmission coefficient of the metal frame (Uf value), the external aluminium shell is thermally separated from the internal one. To do this, insulating bars made from engineering plastics (for example insulbar from Ensinger) are incorporated between the metal profiles, and direct heat dissipation via the aluminium is interrupted. Through this separation, an insulation zone is generated in the interior of the frame assembly. The design engineer has a variety of options available, when creating this zone, for optimising the thermal insulation and bringing about a desired Uf value using construction measures. At the heart of these are the different types of heat transfer.
Types of heat transfer
Heat is energy which, by means of thermal conduction (transmission), heat convection and radiation (emission), always flows towards where the temperature is lower.