Adherence of the insulation in the filling of an air gap

The filling of the air gap of a wall is one of the techniques that can be carried out with polyurethane, as it adheres as required to the walls of the gap, something that cannot be achieved with other insufflated insulating materials such as cellulose, mineral wool or polystyrene beads.

In this article, we will define the most difficult constructive elements to come across when filling the air gap. We propose polyurethane as the optimal insulating material for gaps filling.

Adherence of the insulation in the filling of an air gap


Insulation by air gap filling is performed in double-sheet walls where such a gap exists. By injecting polyurethane from the outside of any of the two sheets, it expands, adapting 100% to the shape and elements in the air gap, as this can be seen in the videos included in the article "The filling of the air gap".


Injecting a polyurethane system into an air gap

Polyurethane injection techniques are highly developed and require different controls during their execution. The first step is to carry out a preliminary study of the condition of the wall in which we want to intervene. It is recommended that the air gap is at least 5 centimeters thick and continuous.

Some aspects to take into account for all types of insulation systems according to Hume Ingeniería are the following:

  • The exterior face of the facade must be in good condition so that the filling material does not come out through possible cracks. If any repair is necessary, it must be taken into account in the planning of the works. Cracks or fissures must be thoroughly evaluated and their origin must be stated, in order to guarantee that once they are resolved, the insulating material will not come out through these cracks and put the sprayed insulation at risk.
  • The mortar joints of the bricks should be inspected to evaluate the existence of cracks or detachments of the mass and, if necessary, they must be repaired.
  • The holes and gaps must be sealed to avoid the loss of insulation.
  • Any element obstructing the air gap can cause a problem in the execution, avoiding the complete filling of the air gap, which will prevent the correct thermal behaviour of the system.

Injected polyurethane repairs the existing fissures, since thanks to its liquid form at first and its solid form later, it adapts to all spaces, thus achieving the highest sealing level. The possible elements contained within the air gap do not prevent injected polyurethane to perform its job in a proper way.


Download our technical sheets of acoustic systems


Problematic areas in the insulation of a façade

The correct treatment of thermal bridges can imply the success or the failure of an insulation within facades that have an air gap. The problematic areas are the following:

  • Holes outline.
  • Facade and slab junctions.
  • Facade and roof junctions.


Injected polyurethane system Phono Spray I-905

Synthesia Technology offers for these cases the Phono Spray I-905 injected polyurethane product.

Phono Spray I-905 is a thermo-acoustic polyurethane system in two components: polyol and isocyanate. The system is applied by casting and injected "in situ", which allows obtaining low-density open-cell rigid foam with good acoustic absorption properties. The application of Phono Spray I-905 in a given constructive solution improves the overall acoustic insulation of this solution.



If you'd like to receive further information on the Phono Spray I-905 system, download the following factsheet of our thermo-acoustic insulating solutions or contact us.


Download our technical sheets of acoustic systems




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