Insulating the exterior walls of a home: principle materials prices and assistance

The effects on our living conditions of galloping demography and oil shocks, led the leaders of developed countries to propose incentives individual intended for reduce consumption household energy. This awareness is materialized, for the building sector, by a series of thermal regulations (RT), aimed at combating global warming. The latest measurement (RT 2020), requires new buildings built in France to produce more energy than they use.

Achieving this regulatory obligation requires, among other measures, theimprovement performance ofisolation of the buildings, which is offered by the insulation from the outside (ITE).

Why is exterior insulation more efficient?

The interest of the ITE is explained simply, if one understands its operating principle. In a building, the materials structural dense (concrete, stone, brick, etc.), act as a accumulator heat or cold, under the effect of the outside temperature. To avoid these undesirable exchanges, an insulating barrier is interposed on the interior walls (walls, ceilings and floors) which slows down their transmission. Unfortunately, the stored calories or cold continue to diffuse into the ambient air of the house, although after the disappearance from the transmitting source.

Reversenow, the conditions of the experiment, by arranging, all other things being equal, the insulating layer no longer inside of the building, but outside. Summer heat or winter cold are now largely attenuated before reaching the wall, whose mass and walls remain closer to the interior temperature of the room. The trades thermal with the indoor ambient air are therefore less violent and the wall fulfills, thus fully, its role compensator. The wall reacts, in a way, as if it were in the presence of a milder climate.

Add the property of insulation from the outside, to radically reduce thermal bridges, representing +/- 15% of losses, you obtain a atmosphere pleasant life, without sudden upward movements of the air or unpleasant vertical stratification.

In short, the ITE improved your comfort of life while saving energy!

When should we choose the method of insulating the walls from the outside?

In new construction, all the architectural factors must be considered. The reduction of thermal bridges is, of course, one of the important assets of ITE, but this technique does not deal with them all. She is Without effect on the thermal transmission by the slabs balconies, on that caused by the ornaments and other protruding external elements (moderators) or on glass surfaces. Certain fixings of insulating panels or cladding can also reduce the performance of the system. The caricatural illustration of the limits for which this mode of insulation must be validated by a thermal study, is that of a building with very wide bayson the facade of which run long balconies concrete and whose panels and/or exterior cladding are fixed by mechanical means poorly designed. In this configuration, the most efficient thermal solution consists of continuously doubling the interior walls, ceilings and floors.

The renovation raises fewer questions. Since the law of 1is January 2017, thermal insulation concerns all work to redesign roofs or fit out habitable premises. The exterior insulation is obligatory if it concerns more than 50 % surface area (excluding openings), façades of the building. Exceptions are however provided for by law:

  • for remarkable or historical monuments;
  • when there is a contradiction with other legal texts;
  • in the presence of proven architectural constraints or inconsiderate additional costs.

The 3 wall insulation techniques, from the outside

Exterior wall insulation systems consist of a layer of insulating materials, glued, projected or mechanically fixed to the load-bearing wall. They have common characteristics:

  • great thermal, heat and cold resistance;
  • reduction of thermal bridges;
  • protection of structural materials against atmospheric pollution;
  • reduction of the risk of surface cracking during deformations of the building;
  • added value on resale.

At the same time, each type of ITE adds its specificities remarkable.

1 – The ventilated facadea system reputed to be the most effective, consists of:

  • an armature of supports, in wood or metal;
  • an insulator slipped between or under the frame elements;
  • a protective cladding, constituting the decorative surface;
  • a mesh air intake at the base of the wall;
  • high ventilation protected by an acroterion.

A lame d’airwith a minimum thickness of 20 mm, but variable depending on the height of the wall, is arranged between the cladding and the insulation, over the entire height of the building. The overheated, lighter air constantly rises and escapes through the upper ventilation (chimney effect). This movement creates vacuum, drawing in cooler air through the low air intake.

For this technique, favor the use of mineral wool insulation in semi-rigid plates, because polystyrene is poor sound insulation. The market offers an almost unlimited range of cladding materials in shape, color and surface condition (fiber cement, wood, stone, porcelain stoneware, terracotta, zinc, aluminium, glass, composite plates, enamel, relief, etc.).

2 – Warm facades implement rigid or semi-rigid insulating plates joined together by a joint of polyurethan foam. The finishing layer is attached to the insulation. This assembly method is well suited to cold seasons, during which it competes in performance with ventilated walls, but is less effective in blocking the strong summer heat.

There are many sub-categories of warm facades:

  • Warm glued facadesuse insulation boards rigid, secured to the load-bearing wall by means of glue dots. This technique, fast and economical, must be executed with rigor, on new and clean walls, to avoid future disappointments. It offers little interest in renovation, because of the cost of preparing and leveling the gripping surfaces.

  • Doweled glued facadesuse the same installation method as the previous technique, but its hold is reinforced by a mechanical fixing (knocking pegs insulating). This precaution extends its field of use to other types of insulation, such as semi-rigid mineral wool plates.
  • Facades on profiles most often use smooth expanded polystyrene (EPS) plates of calibrated thickness. Some manufacturers offer, on this principle, facades entirely prefabricated in the factory. The frame and the fixing systems, metal or PVC, can be hidden or visible. This book is completely removable and recyclable.

The finishing of warm facades is most often carried out:

  • by applying a conventional mineral or organic coating to a metal or composite mesh;
  • using panels to be glued or to be embedded, the finishing layer of which is pre-glued on the insulation (clothing).

3 – Alternative or complementary ITE techniquesmore confidential, are offered by manufacturers: double walls, light facades, synthetic insulating coatings filled with polystyrene beads or silicone airgel, ecological coatings (lime/hemp, lime/cork, etc.), etc.

exterior insulation prices

The ITE is a expensive techniquebut gives the facade the appearance of new, for a long time.

Depending on the process used, the level of insulation, the grip surface and the type of coating, the costs vary between 60 and 100 €/m².

These prices can quickly skyrocket if you want to benefit from a luxurious finishing material!

What financial aid for ITE?

If your house has been completed since more than 2 yearsand that you use the services of a professional EGRyou can benefit from aid and subsidies:

1 – Help accessible to all:

  • TVA reduced to 5,5 %, applicable to work in main or secondary residences. See website
  • MaPrimeRenovreplaces since October 2020 the Tax Credit for Energy Transition (CITE) and Anah’s “Living better agility” aids. Site Information
  • Zero rate eco-loan (Eco-PTZ), intended for the first investment of households. Information on

2 – aid subject to an income ceiling:

  • Aid from the Agency for the improvement of housing (Anah) are centered on the improvement of old or degraded housing, the fight against fuel poverty, etc. Details on the Anah website, section “my helpers“.
  • Housing action (formerly 1% employer), is reserved for low-income private sector employees. Site Information
  • The energy saving certificates (EEC) or energy bonuses are premiums paid by energy suppliers. They vary according to the region and the type of work. Information from your contractor or on the website of the companies concerned.
  • Energy vouchers where the work checks, are intended for disadvantaged households, to meet the usual fixed energy costs and certain energy renovation works. Information on the site

Some local authorities (regions, departments or town halls) or organisms (pension funds, CAF, etc.), exceptionally grant subsidies for work related to energy savings. For current plans in your area, check with your city ​​hall or the website

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