In energy-saving measures, the exterior walls are of particular importance. They form the largest part of the boundary surface of the building envelope and thus the largest part of the heat exchange surface.
For old buildings with a 24 cm thick brick wall, U-value approx. 2.0 W/m²K, the required U-value of 0.24 W/m²K according to the Building Energy Act can be achieved with an additional thermal insulation layer of ETICS of 16 cm (see GEG 2021).
Energy-saving measures are therefore economically and ecologically efficient. The required heat transfer coefficients for walls can only be achieved with additional thermal insulation.
Various analysis methods, e.g. thermography and blower door, can be used to visualize heat losses in the area of the building envelope.
Thermographic
images show the surface temperatures of the building envelope.
Particularly
high heat losses are present over the areas with the red coloration.
A video on
page
explains this process.
The Blower-Door method checks the airtightness of a building and thus detects heat leaks through which warm air flows uncontrolled from the inside to the outside.
The method is explained in more detail in a video at:
Before applying the thermal insulation, the walls must be inspected for any existing structural damage.
The picture shows moisture damage.
Cracks,
surface, and moisture damage in the exterior wall can have many different
causes.
To carry
out a permanent, proper renovation, the damage must be repaired.
Various methods are available to repair the damage: mechanical methods and injection methods
In mechanical processes, continuous horizontal slits are made through the wall of approx. 1m length and sealing materials are installed.
The joints must overlap sufficiently to achieve the moisture barrier.
Injection methods are only suitable for absorbent building materials. Hydrophobic injection agent is filled into boreholes until saturation has occurred.
The hydrophobicity of the capillary prevents moisture transport in the masonry.
Moisture penetrating laterally from outside into the basement walls can rise to the first-floor area by capillary action.
Heat losses are also given via the basement walls. If basement rooms are used as utility and recreation rooms, heat insulation measures reduce energy losses.
For reasons of building physics, exterior insulation is preferable.
Only moisture-resistant thermal insulation materials are suitable.
Insulation on the outside wall prevents the penetration of moisture.
After completion of the necessary renovation work, the thermal insulation measures can be carried out. It is possible to insulate outside or inside.
With external insulation, there are fewer thermal bridges and building physics problems, so it should be preferred. The thermal insulation can consist of different building constructions and building materials, e.g.:
The thermal
insulation plaster consists of the thermal insulation layer and the exterior
plaster.
It is applied
in one or two layers on a dry and load-bearing wall, depending on the chosen
thickness.
The
external plaster is applied to the thoroughly dried thermal insulation plaster.
In addition to single-layer external walls, multi-layer external walls with thermal insulation can be selected.
External walls with a light facing layer consist of a load-bearing external wall, the thermal insulation, and the facing layer.
In these methods, the thermal insulation, e.g. mineral wool, is placed between the supporting framework of the curtain wall.
The facing layer can be made of wood, metal, plastic, or slate, and it forms the end of the ventilated façade.
In
rear-ventilated systems with a heavy facing layer of brick, lime sand, or
natural stone, the insulation boards are attached seamlessly to the exterior
wall in a bond.
The
distance between the facing layer and insulation must be at least 4 cm to ensure
sufficient rear ventilation.
In the case of double-shell walls, core insulation is a good choice as thermal insulation fill.
This can consist of cork shot, polystyrene beads, perlite, or cellulose.
Buildings
that are listed as historical monuments may only be insulated on the
inside.
Internal
insulation creates thermal bridges in the area of the interior walls and
ceilings; it must be checked whether a vapor barrier or vapor control layer is
required.