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 older buildings, the top floor ceiling is often the worst-insulated part of the structure. Timber-beamed ceilings facing a cold roof are usually hollow (with an air gap of up to 20 cm!) or only partially filled with slag or clay. Due to the inadequate thermal insulation of such a structure, heat loss is very high in winter. In summer, on the other hand, the rooms bounded by the ceiling from above heat up so much that living comfort is severely compromised.
First of all, a check is carried out to determine whether there is a hollow layer. To do this, either a floorboard is lifted or a hole is drilled. A folding rule or a stiff piece of wire is inserted into the hole to determine the depth of the hollow layer.
If the cavity is thicker than 3 cm, specialist blow-in insulation contractors will either create small openings in the floorboards or – even more simply – remove a floorboard. A blow-in hose is fed through these openings, and the cavity is filled with blow-in insulation through it. The process is carried out for each cavity; within a few hours, the ceiling is completely filled with insulation and insulated.
As an insulation thickness of 14 cm is not sustainable, additional blown-in insulation of approximately 14 to 22 cm (totalling up to 36 cm) is applied. Insulating the upper surface with insulation materials without filling the cavity is virtually ineffective due to rear ventilation effects.
You can find qualified tradespeople here.
The cavity in the ceiling structure is filled completely. This usually results in an insulation thickness of 12 to 16 cm. The additional insulation layer should be approximately 14 cm thick.
All the benefits at a glance
Thermal insulation: If the U-value of the upper floor slab was previously around 1.3 W/m²K, it can be reduced to around 0.14 W/m²K through insulation measures. This represents a thermal improvement of approximately 90 per cent for the ‘upper floor slab’ component. Heating costs for a single-storey building can be reduced by up to 20 per cent. For multi-storey buildings, the percentage saving is lower.
Summer heat protection: the temperature in rooms beneath uninsulated ceilings can reach up to 35°C in summer. Insulating the ceiling can reduce the temperature by up to 10°C (provided that solar gain through windows etc. is prevented).
Further benefits:
- Comfort is improved due to higher temperatures in the ceiling of the upper floor
- Summer heat protection is significantly improved
- CO₂ emissions are reduced.
- Heating energy consumption and heating costs are reduced
Costs/cost-effectiveness: Depending on the level of difficulty, the total cost of the measure can be up to €60 per m² (varies by region). Thermal insulation can be improved by up to 90 per cent. The measure pays for itself in less than 5 years.
Financial support: This measure is subsidised by the government at 15 per cent of the total costs via the BAFA (an energy adviser is required in each case; an additional 5 per cent is available if an iSFP is drawn up) or via tax relief (Section 35c of the Income Tax Act) – in this case, a 20 per cent tax rebate.
Can I install the insulation myself? No, you need blow-in insulation equipment. However, the costs can be reduced with your help (setting up scaffolding on site, feeding the insulation material into the blow-in machine, cleaning up and dismantling the scaffolding, and also constructing the ‘accessible structure’). Ask the specialist contractor!
