The main role of the insulation is to resist heat transfer through the building envelope.

The insulation must keep the heat inside the building, this resistance to heat transfer, to the outside, is defined as the " thermal resistance ».

When a building is poorly insulated, there are revealing clues such as:

  • Floors and cold walls;
  • High heating costs compared to a building of the same size well insulated;
  • Significant variation in the temperature of surfaces in the same room;
  • Condensation and mold in the structure of external walls;

Condensation and heat losses

Condensation in the structure is the most common problem when insulation is improperly installed or improperly installed.

However, it should be noted that insulation is not the only cause of condensation problems and thermal losses in the building envelope.

In fact, there are components that play an important role, such as the air barrier and the vapor barrier. The air barrier is on the outside of the wall and the vapor barrier on the inside of the wall.

An improperly installed air barrier allows cold air to enter the structure and cause condensation in the structure.

While a poorly installed or absent vapor barrier leaves the interior moisture penetrate the structure and causes a problem of condensation.

The air barrier and vapor barrier must be properly installed, according to the rules of the art, for the envelope to be effective and function as an integrated assembly.

The goal is to ensure the thermal comfort of the occupants and prevent the formation of mold, condensation and rotting of the wood structure.

Building envelope and thermal resistance

At the time of construction, it must be ensured that the components that form the building envelope have the adequate thermal resistance stipulated in the current Quebec Energy Code.

A building engineer must be consulted in order to calculate the total thermal resistance of the exterior wall components and to ensure that condensation (dew point) does not occur in the wooden structure of the exterior walls.

This is to prevent rotting of the structure and the formation of molds and the problems associated with them, such as carpenter ants, infiltration of air or water by the rotten structure, the smell of mold and rotting. etc.

Onesta Building Council

  • Using an infrared camera (thermography), we detect the problematic points with respect to the insulation in the external envelope of the building (the points of thermal losses in the envelope).
  • We also use exploratory holes in the identified areas to examine insulation that may be damp, compacted, improperly installed, inadequate or absent.
  • The building engineer calculates the thermal resistance of the exterior envelope and proposes appropriate solutions (if necessary) to improve the thermal resistance of the building (according to the mandate).


Extruded insulation deteriorated by carpenter ants

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