Comparison of interior or exterior insulation

Comparison of interior and exterior insulation techniques.

- Comparative outer VS interior insulation on the forum
- Forum insulation and heating


Insulation is the best method to save energy: the heating bill for buildings represents about 40% of the overall energy bill in a country, the potential for savings is significant. Insulation (and hunting for air leaks) is the only solution available.

There are 2 methods of thermal insulation: from the inside (ITI) or from the outside (ITE). Let's see the advantages and disadvantages of each method. Advantages or disadvantages which will also depend on the choice of insulating material (breathable or not).

A) From the inside

- Fairly "light" site can generally be carried out by the owner
- Work that can be carried out (piece by piece) according to its means
- Less expensive
- Low thermal inertia (rapid heating of rooms: for example bathroom)

- Depending on the configuration, does not solve the problem of thermal bridges (floors for example)
- Low thermal inertia and almost zero phase shift: less good comfort than ITE
- External wall not protected (frost, infiltration ...)
- Depending on the material, risk of condensation in the insulation: the steam must be properly installed.
- If using insulation with high water vapor resistance: ventilation requires

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B) From the outside

- Heat accumulation in the walls: good inertia and phase shift increasing comfort
- Eliminate thermal bridges (if well done)
- Protection of the existing wall against rain, frost, T ° ...

- More expensive
- Quite heavy site
- Generally: requires scaffolding and construction by a professional
- Requires the addition of ventilation if made with a vapor-tight material
- Finishing protection (plaster) or cladding necessary = additional cost and can be an administrative file (type of facade / region)
- Increases the thickness of the exterior walls: can reduce the light in the home and pose problems of connection at the level of the roof (on thickness)
- Finishing at the sashes can be problematic
- Can alter a facade (local stone for example)


Each method of thermal insulation has its advantages and disadvantages.
We can think of an intermediate solution which would be a compromise between the 2 on a case-by-case basis since each site is unique. It is advisable to use the solution and especially the most suitable materials. For example, nothing prevents you from having exterior insulation or insulating constructive walls (Ytong) and from "over-insulating" your bathroom from the inside with styrodur provided there is adequate ventilation (the use of multipor, breathable, may dispense or greatly reduce the use of CMV).

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- Comparative outer VS interior insulation on the forum
- Forum insulation and heating

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