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
Perimeter insulation refers to the external thermal insulation of building elements in contact with the ground, such as external basement walls and basement floors. This insulation is installed on the outside of the building’s waterproofing and protects the building structure from heat loss and the effects of damp. In accordance with DIN 4108-2, the insulation boards must be made of XPS (extruded polystyrene), laid in a single layer and must not be in constant contact with groundwater. This ensures a comfortable indoor climate in the basement area and keeps the building’s foundations dry.
Where the ground is dry, EPS may also be used as perimeter insulation. In this case, a ground survey is required to assess the specific groundwater conditions and confirm that EPS is suitable for use.
Thanks to its closed-cell structure, XPS exhibits high moisture resistance and thus retains its insulating properties even during prolonged contact with water, such as during flooding. XPS provides effective protection against moisture and mechanical stress, particularly in areas in direct contact with the ground, such as perimeter insulation and foundation slabs. Thanks to these properties, the insulation retains its functionality even during extreme weather events, such as heavy rain and flooding. This is underpinned by building authority approvals and the quality seal of the FPX e.V. trade association, confirmed by FIW Munich.
Application instructions
- Surface preparation: Surfaces must be rough to ensure the adhesion of adhesive mortar, plaster and other mortars. This applies in particular to the plinth area.
- Installation:
- On dry subfloors in accordance with DIN 4108-2: laid tightly butt-jointed in a staggered pattern, with joints offset, and, in the case of multi-layer installation, bonded at specific points.
- In the case of water pressure and accumulating seepage water, in accordance with the type approval: bonded over the entire surface, with joints filled with adhesive (please refer to the manufacturer’s relevant type approval).
- Waterproofing: Use suitable adhesives, depending on the application.
Safety instructions
- XPS should be permanently protected from UV radiation to prevent damage to the material.
- Suitable adhesives must be used for bonding.
Further applications and details
- Perimeter insulation for ground moisture and non-pooling seepage water:
- Single-layer installation in accordance with DIN 4108-2.
- Prevention of thermal bridges by ensuring the boards are laid with tight joints.
- Multi-layer installation to improve the insulating effect.
- Protection of the building waterproofing against mechanical stress
2. Insulation of foundations and foundation slabs:
- Lateral thermal insulation of foundations to prevent frost damage.
- Installation beneath foundation slabs for improved thermal insulation and load transfer.
3. Connections and finishes:
- Professional installation of connections and finishes to prevent thermal bridges.
- Use of suitable materials for waterproofing and adhesives (information provided by XPS manufacturers).
Installation benefits
- Easy to handle and install.
- No special tools required.
- Lightweight and easy to transport.
- No dust.
- No itching.
No special protective clothing required.
Design guidelines
- Thermal insulation design: High requirements for the thermal insulation of building elements in contact with the ground in accordance with DIN 4108-4:2020-11 ‘Thermal and moisture design values’. Minimum thermal insulation for external walls in contact with the ground is required by building regulations.
- Moisture protection design: The external thermal insulation is a water vapour diffusion-compatible system in accordance with DIN 18533.
- Selection of type depending on installation depth: As the installation depth increases, so does the earth pressure on the thermal insulation boards. XPS types with higher compressive strength are suitable for greater installation depths.
Information and general installation instructions
- XPS boards should not be exposed to direct sunlight for prolonged periods.
- For bonding, adhesives must be used that are suitable for XPS boards and the specific application.
Drainage
Drainage is not normally required to protect the perimeter insulation. In the case of particular soil conditions or the building’s location (e.g. on a slope), drainage measures must be provided to divert surface water and seepage water in accordance with DIN 4095.
Backfilling of the excavation
When the excavation is backfilled correctly, XPS boards do not require any additional protective layers. Isolated damage to the board surface does not impair the functionality of the perimeter insulation. Care must be taken to ensure that no harmful shear stresses arise on the building’s waterproofing.
Special notes
- XPS panels must be permanently protected from UV radiation.
- When bonding, adhesives must be used that are suitable for XPS boards and the specific application.
- Where applicable, building regulations must be observed.
- The manufacturer’s instructions must be followed.
Sustainability
CO₂ savings and payback
Over its life cycle, XPS can save up to 600 times as much CO₂ as is released during its manufacture. The CO₂ footprint of XPS is fully offset just one year after installation. This means that the amount of CO₂ released during production is offset within a year by the energy savings achieved.
Lifespan
XPS is renowned for its durability. When installed correctly, XPS lasts for the entire service life of the building, leading to long-term energy savings and making it extremely sustainable.
Recycling
XPS is fully recyclable. The German Extruded Foam Association (FPX e.V.) has established a comprehensive recycling system in Germany. Find out more at:
The insulation should be 100–200 mm thick (depending on the requirements of the specific building)
All the benefits at a glance
Improved thermal insulation: As a rule, the U-value can be improved to a target U-value of around 0.2 W/(m²K) to 0.4 W/(m²K) through professionally installed perimeter insulation.
Lower heating costs: if basement rooms are used as living space (basement flats), the heating energy requirements for these rooms can be reduced by up to 30 per cent
Further benefits:
- Improved living comfort
- Protection against damp and mould
- Energy efficiency and environmental friendliness
- Increased property value
- Extended lifespan of the building
- Possible funding opportunities for the insulation work.
Can I carry out the insulation work myself? No. Professional contractors are required to ensure the work is carried out correctly; they will plan and carry out the insulation work in accordance with local conditions and the building’s requirements.
Insulation materials: XPS or foam glass