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PU foam application fields

The best known applications for construction foam are installation, assembly and the insulation of windows and doors. However, anyone who takes a closer look at a building will be amazed to see where else PU foam is used. From the cellar through to the roof: there is hardly any space in a building where construction foam is not used. Wherever openings or joints need to be effectively sealed or insulated, professionals opt for the practical PU foam cans. The descriptions primarily refer to standard practice in Germany.

Installing windows — much quicker with PU foam (4)

Fast, safe and efficient. These are the advantages of PU foam when insulating window joints. Around 80 % of all windows in Germany are insulated with construction foam. This top ranking is due to its excellent insulating properties. It is also safe to use and can level out unevenness in the building easily and efficiently. Other advantages: window joints can be insulated with assembly foam two to three times more quickly than with mineral wool. This saves time and costs, and offers optimum thermal insulation.

Flexible or hard — the right construction foam for mounting doors (1 and 7)

Doors give houses and apartments a face. To ensure that the doors remain functional for a long time, it is important to select the right PU foam for the mounting task. Hard 2-component PU foams are recommended for installing inside doors. In contrast, highly flexible 1-component PU foams should be selected for outside doors. 

The choice of PU foam depends in its function and application: PU foam is primarily responsible for efficient insulation of building doors. For this task, the construction foam needs to be able to compensate movements of the various elements as a result of temperature fluctuations without ripping. This is why the flexible 1-component foams are the right choice for full-surface insulation of joints. Screws are used for the mechanical attachment. In contrast, insulation is not an issue when installing inside doors, the main focus here is on permanent attachment.

Doors are mounted with PU foam to avoid unsightly screws in the door frame. The right assembly foam for the inside door should be extremely strong so that it can withstand everyday bumps and jolts for many years. This is where the harder and stronger 2-component PU foams come into their own. Sealing is less important in living areas. Here, only 20 to 30 percent of the upright door frame surface needs to be adhered. To attach inside doors it is sufficient to apply the assembly foam at six to eight points.

Renovating and insulation facades (9 and 17)

Energy-saving is paramount: around 80 percent of the facades in Germany are insulated with thermal insulation composite systems (WDVS); these EPS insulation boards are adhered or screwed and adhered to the facade. The first choice for new buildings is the adhesive method using PU foam adhesive because it is almost always certain that the adhesive can be applied to the surface. Adhesion is less expensive and also avoids the creation of thermal bridges caused by wall plugs.

When renovating, the specialist needs to check whether the existing surface is sufficiently strong and suitable for the application of an adhesive. If, for instance, the old plaster is brittle and loose, it is recommended attaching the insulation boards with additional approved plate wall plugs. Polyurethane adhesive foams are suitable for adhesion. The advantage of these foams is that they harden quickly and no further tools are required at the building site. After just two to three hours, work can continue on walls mounted with assembly foam.

But which PU foam should one select? The European Organisation for Technical Approvals (EOTA) has defined binding criteria in its Guidelines ETAG 004 (External Thermal Insulation Composite Systems with rendering) in particular with respect to the resistance and stability of the adhesive connection. Also, manufacturers recommend the use of partially collapsing PU foams, i.e. those that do not expand too much. This is the only way to ensure that the insulating elements do not shift in an uncontrolled manner during the hardening and expansion process. It is also important to check that the foam is officially approved for use with the WDVS. Tradesmen may not use assembly foams other than those approved by the WDVS supplier. This also applies even if the products are similar. The building inspectorate approval will become null and void if these systems are mixed.

Filling WDVS joints (9 and 17)

Whilst there are alternatives to the PU foam for filling open joints when attaching thermal insulation composite systems (WDVS), construction foam is a must. To ensure that no thermal bridges are created in the facade, the tradesman must install the insulation boards precisely with tightly pressed butt joints. However, regardless of how exactly the boards are installed, joints cannot always be avoided. These need to be filled in carefully of course so that the 'full insulation' delivers what it promises. Adhesive mortar may never be used because this will create thermal bridges; it also hinders deformation and can lead to cracks in the facade in the future. Instead, if gaps are large, polystyrene strips are cut to size and are applied to the joints. Smaller gaps are insulated with PU foam. Likewise, these need to be approved by the system manufacturer for this application.

With regard to the currently approved thermal insulation composite systems WDVS, faults and gaps between EPS boards must be closed using equivalent insulation materials. Faults and gaps with a maximum width of 5 mm can be closed using inflammable joint foam (B1-PU foam). This is due to the fact that only inflammable EPS insulation materials are usually used. 

Once the foam has hardened, larger excesses can be cut off with a knife. Smaller excess areas can be removed by sanding before the reinforcement and plaster is applied.

PU foam for insulation roller shutter boxes (6)

High energy losses and annoying draughts: many old roller shutter boxes are not insulated and therefore generate costs and impair living comfort. In times of rising energy costs, lots of home owners have now insulated their roller shutter boxes. Here, too, they opt for assembly foam.

There are various insulation methods, the choice of which largely depends on the preference of the roller shutter or sun protection technician. Some professionals prefer to clad the boxes with highly effective insulation boards and seal the joints with PU foam. Others prefer flexible insulation boards that are simply pushed into the boxes around the roller shutter shaft. Then assembly foam only needs to be applied to the connection of the insulation board and the brickwork on the side. Here, too, it is recommended using elastic 1-component construction foam that is able to withstand movements by parts resulting from temperature fluctuations and wind loads for years on end.

Construction foam for opening through the roof (13)

Any retrofitted cable ducts, venting pipes or even solar systems are faced with a serious problem, namely that the roof needs to be opened up. The joints created here impair the sealing and the thermal insulation of the roof. An ideal construction material for re-insulating the joints is PU foam - especially in inaccessible areas that the tradesman can easily reach with a PU foam gun or the adapter tube.