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
In many older blocks of flats, the top concrete floor slab is situated beneath a slightly sloping timber structure, forming a flat roof or a gently sloping roof. Between the roof waterproofing (bitumen and gravel fill on timber sheathing) and the ceiling of the living space (plastered concrete) there are cavities 20–40 cm thick, which are sometimes covered with only a 6–8 cm layer of insulation. These constructions result in high heat loss in winter, whilst in summer, conversely, the living spaces below heat up rapidly.
Ventilated flat roofs can be retrofitted with insulation at little cost. To do this, blow-in insulation of sufficient thickness is blown into the flat roof without leaving any gaps. The insulation is efficiently fed into the structure via blow-in hoses through existing or specially created openings. The openings created by the specialist blow-in insulation contractors must then be professionally sealed or welded/waterproofed with bitumen by a roofing contractor.
Approx. 20–30 cm thick.
All the benefits at a glance
Improved thermal insulation: If the U-value of the roof structure was previously approx. 2.3 – 1.0 W/(m²K), the insulation work can reduce this to approx. 0.15 – 0.1 W/(m²K), representing a thermal improvement in the component of approx. 90 per cent.
Lower heating costs: Heating costs are significantly reduced. In relation to the roof area, heating costs are cut by over 90 per cent. It is not possible to provide an estimate of the percentage saving for the building as a whole, as this depends, amongst other things, on the height of the building and other factors.
Further advantages:
• There is no need for a complex and more expensive roof renovation involving roof insulation elements, parapet modification and roof covering replacement.
• This insulation method is very cost-effective and pays for itself within a few years.
• Scaffolding is not required.
• Summer heat protection on the top floor is significantly improved.
• The rooms become more comfortable.
• Heating costs are significantly reduced.
• CO₂ emissions are reduced.
• The insulation work can usually be carried out in a single day.
• The work causes no disruption to residents.
• The insulation material can be removed and reused at a later date.
Costs/Cost-effectiveness: Approx. €20–25 per m² depending on the thickness and quantity of insulation, plus any additional work where applicable. For a medium-sized block of flats, this results in total costs of approx. 7,000.00 €, and for a flat-roofed bungalow, approx. 2,800.00 €.
Subsidies: The GEG and BEG subsidy schemes require a U-value of 0.20 and 0.14 W/(m²K) respectively for the insulation of flat roofs; the latter requires insulation thicknesses of up to 30 cm. This individual measure usually meets the U-value requirement.
Can I install the insulation myself? No. This insulation method can only be carried out by a specialist contractor in collaboration with a roofing firm.
