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Insulation from the outside thanks to a double wall

Double wall insulation is an exterior insulation technique that could be described as masonry, in the sense that it involves the construction of a second wall all around the building to be insulated. Here no creation of a frame or use of reinforcement mesh, such as those used by other methods of external insulation, reported doubling and plaster support. Here, the insulation is simply sandwiched between the two rows of walls. An implementation seemingly simpler, but also has its own specificities.

The characteristics of double wall exterior insulation in a few points:

Practicable for a renovation as for a new construction, the insulation by the outside thanks to a double wall makes it possible not to touch the habitable surface of the house, nor having to redo all the interior decoration after work. Only the outer face of the house is concerned. Given the nature of the work that may cause a change in appearance of the facade must first be a work permit.

The characteristics of double wall outer insulation

With this technique, the insulation is first attached to the outer wall of the wall. To do this, it is either glued or mechanically fixed. Then, a second masonry wall is built. It covers the insulation and may or may not include a blade of air according to the needs of construction. In all cases, to ensure a certain unity between these two sections of wall, anchoring devices are arranged at regular intervals. Equipped with a holding washer that holds the insulation, they connect the two walls by fixing at the joints of the walls.

Finally, even if they can be visually similar to the two walls making this type of insulation possible are not of the same nature. In fact, the interior wall from which the insulation starts is by definition a load-bearing wall that ensures the stability of the building. The second wall plays the role of wall facing. It protects the insulation and decorates the outside of your home, but is in no way carrier. On the other hand, it requires very little maintenance.

Factors influencing the thermal performance of double-wall insulation:

The insulation from the outside is already in itself an advantage in the sense that it preserves and does not harm the primary thermal inertia of the load-bearing wall, contrary to what is observed in insulation from the inside. On the contrary, since the addition of layers on the facade is to protect the surface of the wall and at the same time to slow down the phenomena of heating or cooling thereof. The thermal insulation performance is thus improved for greater comfort winter and summer. The phonic abilities are also very interesting.

The calculation of the targeted thermal performance, the quality and thickness of the insulation on the one hand and the constitution of the load-bearing wall on the other. This second point should not be neglected, because even if the insulation from the outside thanks to a double wall is possible on a thin wall (at least 150 mm thick), a thick concrete wall will offer a better insulation base than an end wall of silico-limestone bricks.

Special features of construction with insulation from the outside thanks to a double wall:

Special features of construction with insulation from the outside thanks to a double wall

By the very fact of its constitution and the alternation of low permeability, permeable materials and again not very permeable, with the water vapor, the technique of isolation by the outside with double wall can not allow the humidity natural to escape. This is trapped between the insulation and the wall cladding. To remedy this and avoid the problems due to excessive internal condensation in the wall, it is necessary to think of arranging down the wall of fine drainage openings.

For the same reasons, it will also be essential to have a sealing strip or membrane at the bottom of the walls and battens. The chosen insulation must be compatible with external use and especially not be hydrophilic. Most often, mineral wool is used for this purpose. Finally, if the facing wall is itself permeable to water vapor, if it is covered with a waterproof coating or if it is particularly exposed to rainwater runoff, it will be appropriate to install an air gap between the insulation and the inside face of the facing wall. The function of this air gap does not affect the thermal performance because with the lower openings the air is mobile. But thanks to it, the evacuation of the condensation water will be greatly facilitated.

Video Instruction: How to fix to an insulated wall