Bead-and-dot method: It is essential to ensure that a continuous bead is applied along all edges of the insulation boards. Applying only a few small patches of insulation is not permitted.

Full-surface bonding of the insulation boards: Care must be taken to ensure that the adhesive filler is applied completely and evenly to the insulation board.

Observe the specified overlap: The overlap refers to the extent to which individual insulation boards overlap one another. As a rule of thumb, an overlap of at least 10 cm, as shown in the illustration, should be maintained. Manufacturer’s specifications must be checked in this regard.

Notching at building openings: Notching refers to the process of cutting notches into the insulation boards at building openings. Note: To prevent cracking, the joints between the insulation boards should not run directly to the corners of building openings. The insulation boards should be laid in such a way that the joints are at least 10 cm away from the corners of the openings.

Joints and gaps: Any misalignments at the joints of the insulation battens must be filled with suitable foam sealant to prevent cracking and minimise heat loss. (This must be flame-retardant!) Otherwise, moisture problems could also arise at larger, unsealed joints.

Building corners: At building corners, the insulation boards must be interlocked. To do this, the insulation boards must be glued alternately with an overlap or butted against the protruding board. Once the adhesive has set (approximately 2 days later), the protruding strips can be cut cleanly along a straight edge and, if necessary, finished off with a sanding block.

Diagonal reinforcement: Reinforcement of the mesh around wall openings in corner areas. Diagonal reinforcement, corner reinforcement and surface reinforcement. In addition, the edges of the opening and the building corners should also be reinforced.

Anchor scheme: Due to the wide variety of insulation materials and existing masonry, it is essential to ensure the correct choice of anchors. Particular attention must be paid here to compatibility with the masonry and to the length of the wall plugs. When inserting the wall plugs, it is essential to follow the manufacturer’s instructions strictly. The requirements regarding drill hole depth and the actual wall plug layout must be adhered to without exception. The anchors must be set flush with the insulation material. The resulting recess must be filled with an insulation plug. If the insulation anchors are not set flush, thermal bridge-free ETICS screw anchors from the system manufacturer must be used. If such anchors are not used and even simple hammer-in anchors are not countersunk, unsightly anchor marks may appear on the external render after a few years (algae – often green or grey – often form across the surface, but not in the area of the anchors).

Plinth finish: To protect the insulation boards against intrusion by mice or similar pests, plinth rails must be used in the plinth area to protect the insulation boards from below as well.

Composite thermal insulation system:
The installer should always adhere to the manufacturer’s system and use only compatible system components, as otherwise no manufacturer or supplier will honour the warranty in the event of damage. These systems should have system approval.

Window reveals/thermal bridges: To prevent heat loss, the insulation material must also be installed within the window reveal. If the space between the window frame and the window reveal is too narrow for insulation, the specialist will remove part of the window reveal. Alternatively, a high-performance insulation material such as Spaceloft WLS 015 can be used in a layer thickness of at least 2 cm. A professionally installed external thermal insulation composite system (ETICS) must extend onto the cellar wall to a point approximately 60 cm below the concrete ceiling (floor). Otherwise, the insulation will be ineffective at the level of the (internally fitted) skirting board, and due to thermal bridging effects, there is even a risk of condensation and, in extreme cases, mould.

External render: The external render used with an ETICS does not necessarily have to be mineral-based (see the relevant system approvals). There are organic and inorganic systems available. The advantage of organic systems is that the binder is not cement but often a synthetic resin. As a result, the render remains more elastic and is less prone to cracking. An additional coat of paint is also unnecessary, as these renders do not absorb water.

Woodpecker holes: Woodpeckers love to peck holes in surfaces that sound ‘hollow’ in some way. If you wish to take preventative measures from the outset, you should have the ETICS fitted with a thick-coat plaster system. However, as this is somewhat more expensive, most people choose not to do so. The result: woodpecker holes. These must be filled promptly, as otherwise – particularly on the weather-facing side (where it is exposed to driving rain) – rainwater can penetrate behind the render and the insulation boards, leading to the risk of mould growth on the inside. Incidentally, ‘woodpecker holes’ are a risk with any material used, not just polystyrene.

Why sealing is necessary

• Moisture damage: Rainwater penetrates deep into the external thermal insulation composite system (ETICS) unhindered.
• Mould growth: The dampness causes mould to form, which destroys the insulating effect and poses a risk to living spaces.
• Other inhabitants: Other birds (e.g. titmice, starlings) or rodents and wasps use the holes as nesting sites.
• Energy loss: The damaged insulation layer loses its insulating effect at these points. 

Important rules for sealing

• Respect species protection: Woodpeckers are strictly protected.
• Do not trap animals: Holes must never be sealed if there are still eggs or young birds inside.
• Right time of year: Repairs must only be carried out after the breeding season (usually from late summer or autumn).
• Professional repair: The cavity must be filled with foam, sealed with repair mortar and replastered – ideally using a woodpecker-proof reinforced mesh. 

Also, to prevent heat loss (caused by so-called thermal bridges), the ETICS must be extended downwards from the façade by approximately 60 cm onto the plinth or the basement walls. Ideally, the ETICS should connect directly to the perimeter insulation at this point.

Once the thermal insulation has been fixed in place, the reinforcement mortar is applied, into which a reinforcement mesh is embedded. The purpose of this layer is to absorb any expansion stresses that may arise.
The final finish of the ETICS is applied over the reinforcement layer. The exterior render – for example, a lime-cement render or a thin-coat render – gives the old façade its new, externally visible appearance.

Please note: As with any insulation project, the costs are divided into ‘fixed costs’ (scaffolding, plaster treatment, adhesive, wall plugs, reinforcement mesh, base coat, finish coat, new downpipes, new window sills, subsequent painting, the painter’s/plasterer’s labour, etc., etc.) and ‘variable costs’ (cost of insulation material, depending on the thickness of the insulation). The ‘fixed’ costs can account for up to 90 per cent of the total costs. From an economic point of view, an ETI system that is of insufficient quality (too thin) can never be rectified!

ETICS and new windows: see attached PDF

Please note: An external thermal insulation composite system is only fully functional if there is no air gap in the external wall, as this would severely limit the effectiveness of the external insulation due to rear-ventilation effects. This could be caused by double-skin masonry with an air gap, which is particularly common in northern and western Germany. In such cases, the existing air gap must be sealed using blow-in insulation before installing an ETICS.

Which insulation materials are suitable? There is a wide range of approved insulation systems for external thermal insulation composite systems, based on:

• polystyrene
• Rock wool
• Aerated concrete
• Soft wood fibre boards
• PU boards
• Phenolic resin rigid foam boards
• in the window reveal, aerogel products where applicable

Important: It is essential to remain ‘within the system’ specified by the ETICS manufacturer, i.e. to use only the building material components designed to work together within that system, as otherwise no manufacturer will accept liability in the event of a complaint.

Who carries out the work? The installation of an ETICS is usually carried out by specialist contractors. These are primarily painting, plastering or stucco contractors.

What needs to be taken into account when planning an ETICS? If windows or doors are also to be replaced as part of the building renovation, this work must be coordinated with the installation of the ETICS. In this case, the windows can optionally be fitted directly into the insulation layer.

Fire safety: Pay particular attention to the fire safety regulations for plinth insulation and fire barriers above windows or between storeys, especially in multi-storey blocks of flats, or use non-combustible insulation materials for external wall insulation.

Practical guide to fire safety: 

All the benefits at a glance

Improved thermal insulation: If the so-called heat transfer coefficient (U-value) of the external wall was previously approx. 1.4 W/(m²K) (watts per square metre per kelvin), the insulation work can reduce this to below 0.2 W/(m²K) and as low as 0.13 W/m²K. This represents a thermal improvement to the ‘external wall’ component and thus a reduction in energy losses of up to 90 per cent.

Lower heating costs: With an ETICS system installed on the external wall, the building’s heating costs are reduced by up to 35 per cent (depending on the proportion of the wall’s surface area covered and its initial condition). See also Passipedia.

Further benefits:

• Living comfort is enhanced due to higher temperatures on the inside surfaces of the external walls
• Mould growth is prevented, as the inner surfaces of the external walls become warmer and therefore drier
• CO₂ emissions are reduced
• A modern, improved appearance of the façade thanks to a wide range of design options

Costs: Depending on the size of the building, its location in Germany, the chosen insulation material and the required insulation thickness, costs range from €150 to €200 per m² of surface area to be insulated.

Funding: The installation of an ETICS is eligible for a tax incentive of 20 per cent or up to 20 per cent of the total costs (as part of an individual renovation roadmap (iSFP); without an iSFP, 15 per cent) in the form of an investment grant. The process is administered by the Federal Office for Economic Affairs and Export Control (BAFA). The eligible investment amount is capped at €60,000 per calendar year and per residential unit, and at €600,000 per building. To receive the funding, you must engage a qualified energy consultant before work begins.

The most cost-effective insulation thickness:
(Cost structure: average price level in Germany, standard house, costs quoted by a specialist painting contractor)

Can I install the insulation myself? No. The installation of an ETICS must be carried out by a specialist contractor. Of course, this does not apply if the homeowner is a qualified tradesperson themselves (painter, plasterer) – in which case, however, only the material costs are eligible for the grant (from €2,000), which must be certified by an energy consultant.
For everyone else, the following applies: costs can be reduced by carrying out some of the work yourself.

Manufacturers