Comparison of the insulation inside or outside

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Comparative isolation techniques from inside and outside.

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


Insulation is the best method to save energy: the building heating bill represents about 40% of the total energy bill of a country, the earning potential is important. The insulation (and the hunt for air leaks) is the only existing solution.

There 2 methods of thermal insulation: from the inside (ITI) or outside (ITE). See the advantages and disadvantages of each method. Advantages or disadvantages also depend on the choice of the insulating material (breathable or not).

A) For the internal

- Quite "light" jobsite can usually be done by the owner
- Works feasible to As (piece by piece) according to his means
- Less expensive
- Low thermal inertia (quick heating parts, eg bathroom)

- Depending on the configuration, does not solve the problem of thermal bridges (eg floors)
- Low thermal inertia phase and almost zero: comfort worse than ITE
- Exterior wall not protected (gel, infiltration ...)
- Depending on the material, risk of condensation in the insulation: The steam must be well posed.
- If using an insulator with a high resistance to water vapor: requires a breakdown

B) From the outside

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

- More expensive
- Construction heavy enough
- Generally: requires scaffolding and achieving a professional
- Requires adding a ventilation if carried out with a steam-proof material
- Protection finish (plaster) or siding required = additional cost and can be administrative file (type of façade / region)
- Increases the thickness of the exterior walls: can reduce the light in the house and ask connection problems in the roof (of thickness)
- Finish at the opening can be problematic
- Can distort a façade (stone of such countries)


Each thermal insulation method has its advantages and disadvantages.
We can think of an intermediate solution that would be a compromise between 2 case by case since each site is unique. It is advisable to use the solution and especially the most adapted materials. For example, there is nothing to prevent external insulation or insulating constructive walls (Ytong) and to "isolate" the bathroom from the inside with styrofoam provided there is adequate ventilation (the use of multipor, perspiring, can dispense or greatly reduce the use of a VMC).

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


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