Energy requirements for existing roofs as well as ceilings and walls separating heated rooms from unheated attics
Concerning roof areas as well as ceilings and walls separating heated rooms from unheated attics, Annex 3 lists the following measures as triggers
- replacement or first-time installation of roof (including dormers) separating heated rooms from outside air as well as of walls and ceilings separating heated space from unheated attics; here, a u-value of 0.24 W/(m²·K) is required for the surfaces concerned;
- replacement of the outer membrane of a roof constructed with a watertight layer (i. e. typical flat roofs over heated space) with a new layer of similar function; here, a u-value of 0.20 W/(m²·K) is required for the surfaces concerned;
- replacement or reconstruction of roof coverings of other types of roofs above heated space (i. e. typical slanted roofs with shingles or roofing tiles as well as the opaque surfaces of dormers) including battens and sheathings underneath the covering; here, a u-value of 0.24 W/(m²·K) is required for the surfaces concerned;
- replacement or installation of sheathings or boarding or adding of thermal insulation on the cold side of walls and ceilings separating heated space from unheated attics; here, a u-value of 0.24 W/(m²·K) is required for the surfaces concerned;
if more than 10% of the roof area (including the opaque surfaces of dormers and the surfaces of walls and ceilings separating heated space from unheated attics) of a building are subject of the measure. A further precondition for all trigger measures is that the components are parts of the envelope of heated space.
Roof components 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 the U-values required in Annex 3 could not be proven by accompanying studies in general. This does not, however, mean that in individual cases the cost effectiveness cannot be achieved.
In case that a refurbishment measure for the roof exclusively implies insulation between the rafters, it is sufficient to fill out the available space between the rafters 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. A respective provision applies if for the measures mentioned above the possible thickness of the insulation layer is limited for technical reasons (e.g., due to necessary connections to other building components).
The requirements are 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%.