What are the benefits of external wall insulation?

Weber Colombia

External wall insulation makes it possible to insulate a home by fitting insulation to its external walls. This can improve thermal performance and reduce energy consumption. EWI offers multiple advantages for both renovation and construction.

1 - What work does external insulation involve?

External Wall Insulation (EWI) consists of applying several layers of render and insulation to a home’s external walls:

  • insulation layer: polystyrene, mineral wool, resole foam
  • glass fibre matting
  • undercoat render and primer
  • topcoat (paint, render, etc.)

The fitting method (adhesive, nails, pegs) is determined by the location of the home, its altitude, its aspect and the local weather conditions.

The condition and type of the substrate (external walls) also determine the appropriate product solution and fitting method.

The home is habitable during the works, which take place exclusively outside. The inside area is not reduced, unlike with internal insulation, which can reduce the habitable area by up to 7%).

The duration of EWI works depends on the area to be renovated. Works take 3 weeks, on average, for a 100m² home.

2 - Improving the home’s thermal performance

External wall insulation improves the walls’ thermal inertia. With layers of insulation added to the wall, EWI limits heat loss.

  • improves the home’s thermal comfort
  • reduces heating costs
  • limits CO2 pollution
  • limits energy costs of accessories (heat pump, air-conditioning, fans)

3 - More comfortable living spaces

Excessive damp in a home is due to heat loss through the walls. Water vapour condenses on cold walls and in the least-insulated corners. Damp appears at thermal bridges, resulting in paint and plaster degrading, wallpaper coming unstuck, and the development of mites and moulds. Damp homes cause or exacerbate respiratory problems.

Effective external insulation of a home limits the effects of condensation and eliminates a large number of thermal bridges.

Thermal bridges account for up to 40% of heating power consumption and 5 to 25% of heat loss (Source Ooreka).