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Retrofit insulation of top storey ceilings

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Obere GeschossdeckeSource: Fotolia


Insulation of the top story ceiling against an unheated attic is a simple and normally cost-effective measure to improve the energy performance of a building. Against this background, the Energy Saving Ordinance for many cases requires mandatory retrofit insulation.

The possibility of making a personal contribution may be considered. Depending on the usage of the attic, it should be decided whether the insulation has to be walkable or not. It is recommended to allow at least partial accessibility for inspection and maintenance work.

If an extension of the roof is planned in the near future, one should consider insulating the roof instead of the top story ceiling.
The achieved energy cost savings of a thermal insulation of a top storey ceiling also depend on the initial state.

U-values of selected constructions

The energy quality of the top storey ceiling is dependent on the existing construction. Depending on the age of the building and the region, different design variations may exist. The age of the building alone only permits a limited inference of the energy quality.

The following table shows exemplary U-values for frequent constructions. Ceilings are generally designed wooden or solid constructions.

Construction systemYear of
construction
Structure of building elementU-Value
W/(m²·K)
Timber beam ceilinguntil 191816 cm timber beam / puddle clay, 2 cm shelves, 2,5 cm floor board1.13
Vaulted ceilinguntil 194812 cm vaulted ceiling solid brick, 12 cm flooring sleeper / filling, 2,5 cm floor board1.10
Concrete ceiling1919-4916 cm concrete ceiling, 6 cm bounded screed1.94
Concrete ceiling1949-5715 cm concrete ceiling, 2,5 cm insulation, 1 cm floor screed0.93
Concrete ceiling1969-7814 cm concrete ceiling, 4 cm insulation, 4 cm floating floor screed0.68
Concrete ceiling, insulated*refurbished15 cm concrete ceiling, 4 cm insulation, 4 cm floating floor screed, 12 cm insulation0.22

[Source: Zentrum für Umweltbewusstes Bauen e. V.
"Katalog regionaltypischer Materialien im Gebäudebestand mit Bezug auf die Baualtersklasse und Ableitung typischer Bauteilaufbauten", 20.10.2009
* own calculations (solidar planungswerkstatt using www.u-wert.net)]

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