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5 questions to understand the insulation of the new house

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THEisolation of the house is an important position in the costs. It is also a good investment who is profitable quickly thanks to energy savings that it generates.

What is home insulation for?

THEthermal insulator is a material that transfers very little heat. It is placed on the exterior walls of the house (floors, walls, ceiling), in order to maintain a temperature more or less challenge inside. Indeed, in a heated room, the hot air always tries to escape. THE heat loss are mostly done by roofing (30%), the walls (20%), the windows (15%), the low floor (10%), air renewal (ventilation and leaks) (20%), thermal bridges (5 to 10%).

Heat loss in the house


What thickness of thermal insulation?

THEhouse insulation thickness will be defined at the time of the thermal study. Everything will depend on the building design, its location, of its solar gains, constructive solutions and amenities choose. Depending on the location of the house in the South West, insulation thicknesses vary. And they are generally much lower than what can be found in the North of France. Indeed, respect for Thermal Regulations 2012 imposes a optimized frame, regardless of energy equipment. This means that the building itself should have low heating, cooling and lighting requirements. Increase insulation thickness is one of the ways to achieve the objectives of the RT 2012.

In France, new houses are most often insulated from the inside.

Home insulation: inside or outside?

Floor, wall or roof, insulation can be done from the inside (ITI) or outside (ITE). When we talk distributed insulation, the load-bearing wall itself is insulating.

– Insulation of exterior walls

ITI is the most common solution in France. I'thermal insulator is placed between the internal face of the masonry and the plaster lining. In ITE, uncommon in new construction, it is placed between the wall and the exterior coating or cladding. These two solutions each have their advantages and disadvantages.

– Insulation of the roof

There are two possibilities. The insulation can be placed on the last floor, that of the attic. We then speak of lost attics. If you want to make the entire volume of the house habitable, you can insulate the roof directly under or over slopes.

– Floor insulation

In the same way the insulation takes place on the first floor. The thermal insulation will be placed between the slab and the screed intended to receive the floor covering. In ITE, the insulation is placed under the slab face.

– The insulation of the house in wood construction

Insulation is usually positioned between the supporting studs of thewood frame. Very often, another layer of insulation is added on the interior or exterior side of the wall. In this case, we are talking aboutmixed insulation.

View Diagram explaining the construction technique of the wooden houses of Sic houses.

What is a thermal bridge?

Whatever method is used, the insulation is effective, if she is keep on going. If any part of a wall is not insulated, hot air will rush there, causing a considerable drop in the energy efficiency of the house. In addition, water vapor will condense at this point, leading to mold growth.

The main thermal bridges are found at the various junctions between the walls or different materials: floor-wall connection, roof/wall, window/wall, etc.

Thermal bridges are more easily dealt with in new construction. ©Ademe

Why combine insulation and ventilation?

For the insulation to be effective, it is also necessary to ensure theairtightness buildings. This avoids the entry of parasitic air. Thus, airtight membranes are generally placed between the exterior walls and the insulation. Thus, we understand that the ventilation of these thermally very efficient houses must be well thought out. To renew the indoor air and ensure healthy air for the occupants of the accommodation without loss of untimely heat, a VMC (controlled mechanical ventilation) is installed.

See article How to Ensure Indoor Air Quality in a Home RT 2012



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