Roof
roof pitch
Drempel
Flat roof
Upper floor slab
Solid ceiling
timber-beamed ceiling
Nail binder
Attic conversion
External wall
Façade
Partition joint in a house
cellar wall
Ground floor
cellar ceiling
Stairway to the cellar
Solid ceiling
Cap ceiling
Timber joist floor/cavity
Special components
Often, old roofs only have rudimentary insulation. Thermal insulation is extremely poor, heating costs are high, and in summer it becomes unbearably hot in the loft flats. If roofs are due for a new roof covering anyway, it therefore makes perfect sense to also replace the roof insulation and double it to a sustainable level.
With this insulation method, it is not possible to carry out the work yourself; it is carried out by roofers.
First, the existing roof cladding is removed from the outside to gain access to the rafters. Any existing, poorly installed insulation is then removed. Next, a vapour barrier is installed in a loop pattern within the rafter spaces or over the existing rafters; this must be bonded to ensure an airtight seal. As the existing space between the rafters is insufficient for effective insulation, the rafters are raised outwards/upwards; this can be achieved by attaching a rafter expander to the side. A waterproof underlay membrane (= ‘water-bearing sub-roof’) is then installed on top of these. Next, the counter-battens and roof battens are fitted. Fibre insulation can then be blown into the resulting cavities.
As an alternative to the underlay membrane, an on-roof insulation board can also be installed, followed by vertical counter-battens and horizontal roof battens.
The final layer is the new roof cladding, which can be finished in various ways as required.
The total insulation thickness should be at least 30 cm (or more).
All the benefits at a glance
Improved thermal insulation: If the so-called heat transfer coefficient (U-value) of the roof is 1.2 W/m²K (watts per square metre per kelvin) before insulation work is carried out, this can be improved to 0.14 W/m²K. This means the thermal insulation is 9 times better than before.
Lower heating costs: Depending on the type of building and its structural condition, this measure can reduce the building’s heating costs by up to 25 per cent.
Further benefits:
- Draughts are eliminated
- Winter comfort is enhanced due to higher temperatures on the inside of the sloping roof surfaces
- Mould problems are eliminated
- Summer heat protection is significantly improved
- CO₂ emissions are reduced
- A new, durable roof is created
Financial support:
If the insulation thickness is at least 30 cm (preferably more!), this measure is subsidised by the state at a rate of 15% (BEG) or 20% (tax relief).
Can I install the insulation myself? No, but you may assist with the work. Please contact a specialist contractor for this.
Insulation materials: mineral wool, such as glass wool or rock wool; wood fibre insulation boards; blown-in cellulose insulation; glass wool mats; rock wool mats