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
The ceilings of crawl spaces (i.e. the ground-floor floors) are often uninsulated and have a limited height of 30–50 cm, which makes it impossible to walk on them or carry out work there. Crawl spaces are located beneath the ground floor and often serve as access points to important utility pipes and installations. Due to their location directly above the ground, crawl spaces can be affected by damp.
The ceilings of crawl spaces cannot be insulated using slab or mat insulation materials. It is possible to completely fill them with hydrophobic blow-in insulation materials such as polystyrene beads or to spray the underside of the ceiling with PU spray insulation (provided there is sufficient headroom).
First of all, the crawl space must be thoroughly prepared by cleaning it and checking for any damage or damp problems. Ensure that the crawl space is dry and in good condition.
If the crawl space has a height of 50 cm or less, it is not possible to insulate the ceiling from below. In this case, the crawl space should be completely filled with a moisture-resistant insulation material. Polystyrene beads are a suitable option for this. The crawl space is filled completely.
If the crawl space is 50 cm or more in height, the ceiling can also be insulated from below using polyurethane spray foam. The total insulation thickness should be at least 20 cm.
It is not necessary to install a vapour barrier on the underside.
The thickness of the insulation is determined by the cavity in the crawl space; when the cavity is completely filled, care must be taken to ensure that no gap remains between the blown-in insulation and the ceiling.
When using polyurethane spray foam, a thickness of at least 20 cm should be achieved.
All the benefits at a glance
Lower heating costs: Depending on the initial condition of the crawl space and the quality of the insulation, savings of up to 30 per cent – relative to the ground floor – and more can be achieved. Heat transfer downwards is prevented.
Further benefits:
- Protection against damp and mould.
- Improved indoor climate on the ground floor and greater living comfort. ( = ‘warm feet’)
- A sustainable and environmentally friendly solution.
- Increased property value.
- Long-term cost savings through reduced heating bills.
- Any future infestation by mice, rats, raccoons, etc. is ruled out! (Polystyrene beads are like quicksand to these animals; they cannot move about in them and would perish, which is why these animals will avoid the structure in future.
Subsidies: The GEG and BEG subsidy schemes require a U-value of 0.24 and 0.20 W/(m²K) respectively for insulation measures on floor slabs or ceiling structures exposed to the outside air. As the U-value of the ceiling falls below 0.1 W/m²K, this measure is eligible for a 15 per cent grant (or 20 per cent upon presentation of an iSFP).
Can I carry out the insulation myself? No. To ensure that the polystyrene beads fill the entire cavity securely, a professional contractor with blow-in insulation equipment is required. However, you can reduce the costs by helping out (by feeding the insulation material into the blow-in machine). Ask a specialist contractor!
You can find specialist companies in your area here