Exterior insulation: methods and materials

Effective thermal insulation can make a significant contribution to saving heat energy and thus also heating costs, especially in the cold season. The external insulation is particularly often used for this because the potential for saving is particularly high here and the heat output through the outer shell of the building can be significantly reduced.

Process for facade insulation

In the following, the most important methods for external insulation are briefly presented. Homeowners who intend to insulate their home should also consider the funding options when comparing prices. Funding for energy renovation can be obtained through the Kreditanstalt für Wiederaufbau (KfW) and significantly reduce the overall costs of a measure. This applies to individual measures as well as complete renovations.

As a comparison feature of various insulation systems and insulation materials, the heat transfer coefficient (U-value) can be considered. A low U-value indicates a low heat permeability. The unit is W / (m²K), ie watts per square meter and Kelvin. However, the U-value characterizes only components, not the materials themselves. Thus, the U-value of a concrete wall can be calculated, but not of concrete itself.


One of today's most commonly used methods for external insulation is the thermal insulation composite system. In this process, the facade is wrapped from the outside with a layer of insulating materials. Usually insulation boards are used, which are glued or screwed. Subsequently, a reinforcing fabric is placed over it and finally applied plaster. As insulating material is used in most cases polystyrene, since it is relatively cheap. Alternatives are inorganic materials such as rock wool, glass wool, gypsum or mineral foam. But organic materials such as hemp, cork or wood fiber can be used for insulation. The cost of insulation of this type depends heavily on insulation thickness and materials used. Therefore, they are between 90 and 150 euros per square meter.

Cavity wall insulation

A core insulation requires a two-shell masonry. So between the two wall shells is a cavity that can be used for the purpose of insulation. For this purpose, foam or loose insulating material is used, which is pressed or blown into the cavity from the outside. The material prevents the air convection and thus also a heat release to the outside. How effective the insulation ultimately is depends on the thickness of the cavity. The more space available, the better the insulation. As Dämmmaterial example cellulose insulation can be used, as is the case with the Thermofloc system. The blow-in insulation is characterized by a particularly favorable cost / benefit ratio. The price per square meter is, depending on the thickness of the wall and used material, between 15 and 30 euros.

Thermal insulation plaster and energy-saving colors

A comparatively simple method of thermal insulation can be found in the thermal insulation plaster. By means of a relatively small layer thickness, a good result can be achieved with hitherto completely uninsulated facades, which, however, does not reach the insulation capabilities of the above-mentioned methods. The method is especially an alternative if it is not possible to install insulation boards on the façade and there are no cavities for blow-in insulation. Even with the so-called energy-saving colors can already achieve an effect. This is done by reducing the emissivity of the surface. So this gives off significantly less heat radiation to the outside. Especially with energy-saving paints is to be noted that there are many rather dubious providers whose products do not develop the promised effect.

Video Board: Insulation - types, features, and flaws