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Insulation of lost attics

The insulation of the lost roofs clearly indicates by its name that the insulation techniques used in this context are not intended to make them habitable. Indeed, in the majority of the cases, it amounts purely and simply to condemn the space which could have become an attic to see an additional room under the roof. A possible loss of surface to make the rest of the house more comfortable from the thermal point of view.


The insulation of the attics lost, a large choice of techniques available:

A large number of techniques have been developed to achieve the insulation of lost attics of a building. To do this, it is possible to operate from the inside, but also from the outside. To determine the possible attic insulation process, it is necessary to identify the type of structure present: traditional or industrial.

Insulation of lost attics

The best known attic insulation remains the application of insulating panels or rollers on the ground as well as the use of loose insulation that can be either blown or spilled. But it is also possible to isolate directly between the joists, to insulate from below with a reported ceiling, to position insulation in rolls between the trusses and the tie-rods or for the insulation by the outside, to make pass the insulation over the sandbox before joining it to the floor insulation.

In most cases, attic insulation processes respond more to need than sacrifice. Many attic configurations do not really lend themselves to habitable configurations. For example, industrialized structures can take up a lot of space or be very cumbersome, especially when they are in M ​​or W.

Insulating performance and creation of thermal bridges:

Attic insulation performance

It is very important to insulate your attic space to save energy. Indeed, it is estimated that nearly a third (30%) of heat losses pass through the attic and roof. Especially since the thermal performance can have a very high potential since here the thickness of the insulation is no longer a brake.

But obtaining good performance can only be achieved if the continuity of the insulation is ensured. A law to which we must not derogate if we want to avoid or minimize the creation of thermal bridges punctual. This continuity of insulation must especially be the object of precautions at the level of the load-bearing walls, especially if it is question of insulation by the outside. This, while ensuring a good ventilation of the attic and the frame in general, to avoid the accumulation of moisture and ensure its effectiveness over time.

Installation and use of vapor barrier in attic insulation:

Of all, the installation of the insulation of the roofs lost by blowing is the one that gives the best results. The blowing allows a much better dispersion than the manual spreading, because it makes it possible to fill inaccessible zones and recesses. Nevertheless, it is very difficult for a non-initiated to have access and especially to know how to handle the necessary equipment as it should. That's why it's better to hire a professional to do the job. For installation on the floor or between the joists, it is quite conceivable for a skilled handyman to carry out the realization itself.

There are then two possible scenarios, either the insulation is equipped with a vapor barrier or it is naked. In the second case, it is advisable to use a built-in vapor barrier to be installed just before the insulation, the great advantage of which is to ensure a good seal at the level of the insulating layer rupture due to the joists or level of the junction between the insulation strips. For joists, consider providing a width of insulation a little larger than the gap to ensure a very compact insulation.

In addition, it is advisable to optimize the insulation of the floor of the attic space by superimposing two layers of insulation, one over the other, in cross pose. The first with vapor barrier and the second, perpendicular to the other and without vapor barrier. This crossing cancels the emergence of thermal bridges. Finally, know that it is always possible to make a floor or a corner of floor inside your attic lost to be able to move there more easily or to create a space of storage resting on the joists.


Video Instruction: Insulated attic door