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
Description of the existing structure
Solid roofs are the standard in the flat-roof sector. Solid flat roofs consist of a supporting structure made of non-combustible, mineral-based building materials such as reinforced concrete. They can withstand high mechanical loads, have good heat storage capacity and provide good sound insulation. Roof greening, accessible solar roofs or roof terraces allow the roof areas to be utilised in a climate-friendly manner.
How is insulation installed?
If the existing insulation layers are still functional, dry, dimensionally stable and securely in place, they can be retained in the roof structure. A vapour barrier is installed above the supporting structure. The insulation elements are then fixed in place. Either a bitumen membrane or a plastic membrane can be used as the roof waterproofing.
If the flat roof is to be used as a green roof or a solar roof, insulation that is permanently pressure-resistant and durable is required. For solar roofs, for example, the permissible continuous compressive stress (associated with a compression < 2%) for PU insulation boards can be set at 20 per cent of the compressive strength in accordance with EN 826.
Loosely laid waterproofing membranes and insulation elements can be secured against wind suction, for example, by means of a gravel bed, slab coverings or green roof structures.
Insulation thickness
The required thickness of the insulation material depends on the thermal conductivity of the insulation used. When using aluminium-faced polyurethane flat roof insulation (design thermal conductivity of 0.023 W/(m²·K)) on a solid concrete slab, an insulation thickness of 120 mm is sufficient to achieve a maximum U-value of 0.20 W/(m²·K) and to meet the GEG requirements for the refurbishment of residential buildings. The eligible standards BEG EM or ESanMV (U-value ≤ 0.14 W/(m²·K)) can be achieved using polyurethane panels with 160 mm thick insulation.
All the benefits at a glance
Lower heating costs: Well-planned and effective roof insulation always leads to significant savings on heating costs. It is not possible to give a percentage saving for the whole building, as this depends heavily on other factors (the height and volume of the building, ventilation, heating, windows, etc.).
Further benefits:
- Heat protection in summer: A more comfortable indoor climate.
- Preservation of value: Extends the service life of the roof.
- Environmental friendliness: Reduced energy consumption and CO₂ emissions.
- Efficient use of space: Flat roofs do not require sloping roof surfaces. As the insulation is installed above the supporting structure, the usable space is fully retained.
- Optimised use of roof space: When using a permanently compressive-resistant insulation material, solid flat roofs offer great potential for utilising the roof space, e.g. through green roofs, solar panels or roof terraces.
- Better working conditions: A more pleasant indoor climate for staff.
Funding
Funding: All costs associated with this measure are eligible for tax relief at a rate of 20 per cent or, under the BEG (Federal Funding Scheme for Energy-Efficient Buildings), for a grant of up to 20 per cent (as part of an individual renovation roadmap, iSFP) of the total costs in the form of an investment grant.
The BEG funding scheme is administered by the Federal Office for Economic Affairs and Export Control (BAFA). Some towns or local authorities offer additional funding. Qualified energy efficiency experts can assist you with your funding applications.
Can I install insulation myself?
No, it is important that the work is carried out by experienced professionals to ensure it is done properly and to achieve the best possible results. Proper insulation improves the building’s energy efficiency and helps to reduce energy consumption.