Energy requirements for existing exterior walls
Concerning exterior walls, Annex 3 lists the following measures as triggers
- replacement or first-time installation of an exterior wall,
- installation of sheathings in the form of plates, sheets or comparable elements or boarding, as well as revetting exterior walls using brickwork
- replacement (means: removal and refitting) of exterior plaster
if more than 10% of the exterior walls of a building are subject of the measure. The current EnEV 2013 requires a U-value of 0.24 W/m²K for the concerned parts of the exterior wall after these modernisation measures.
The requirement is also fulfilled if, after the changes to the building envelope, the requirements of a similar new building according to EnEV (level 2014) are not exceeded by more than 40%.
Exterior walls that were constructed or renovated – meeting the energy performance requirements – after December 31, 1983 are excluded from these provisions. In these cases, the legislative authority assumes that the requirement level of the Thermal Insulation Ordinance 82/84 is met: For this assumed level before the measure, the cost effectiveness of an improvement to a U-value of 0.24 W/(m²·K) could not be proven accompanying studies in general. This does not, however, mean that in individual cases the cost effectiveness cannot be achieved.
If the possible thickness of the insulation layer is limited for technical reasons (e.g., due to necessary connections to other building components), the highest possible insulation layer thickness, with respect to acknowledged rules of technology, must be filled out completely using an insulation material of a maximum thermal conductivity of λ= 0.035 W/Km (WLG 035). If an insulation consisting of renewable material is selected or if the insulation measure is carried out using blow-in technologies, a deviance to a maximum of WLG 045 is permitted.
After the current EnEV got into force, measures of the interior side of an exterior wall as well as those refurbishment measures that exclusively consist of thermal insulation of an exterior wall are no longer considered as triggers for conditional requirements according to Annex 3. The installation of a thermal insulation composite system also is not causal for a requirement concerning the resulting u-value as far as this measure is not combined with the installation of sheathings, boarding or the revetting exterior walls using brickwork or serves as the replacement of plaster.
The regulator’s motivation for the abandonment of such requirements was that investors who intend to voluntarily carry out reasonable thermal improvements should not be dissuaded from doing so by too ambitious requirements.