To obtain a thermally homogenous home and reduce heat losses properly, provide comfort in winter and summer, all surfaces in contact with the outside (roof, wall, loft) must be insulated.

All walls and the roof in particular must be insulated

The thermal performance of insulation must be very high in the roof. In winter and summer, strong thermal resistance in the loft is essential.
In winter, losses are at their maximum through all opaque and glazed surfaces and structural links. 
In the summer, direct sunlight on the walls and roofs - particularly exposed - can overheat the interior temperature. The same goes for windows which need outside shutters, blinds, awnings, etc to deflect direct sunlight from the house.

The specific case of old houses

Very old walls can be thick (about 1 metre). But despite their thickness, they do not provide sufficient insulation and comfort nor do they reduce energy consumption properly. They therefore need to be insulated. This is especially true for buildings erected after 1945 which often do have very thin concrete walls.

Thermal resistance and wall thickness

To obtain satisfactory performance with respect to current construction criteria (thermal resistance at R=3), the following wall thicknesses would be needed:

  • 10.5 metres in granite,
  • 4.2 metres in concrete
  • and only 12 cm of insulation (λ =40)

In a home that is not properly insulated, heat escapes through:

In a properly insulated home, heat transfers are reduced on all surfaces, both in summer and winter. Controlled mechanical ventilation optimises air renewal to keep losses down to a minimum.

Depending on the orientation, the size of windows and the occupiers’ lifestyle, free energy through sunlight can represent up to 20% of energy consumption and reduce the heating bill accordingly.

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