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Insulation

Insulating the foundations and insulating the roof of your home will help it withstand extremes of cold or heat while maintaining a comfortable indoor temperature, thereby avoiding exorbitant energy bills.

Without adequate insulation, your house risks losing substantial amounts of heat. Depending on the configuration of your house, heat loss may be broken down as follows:

  • 17% through above-ground walls;
  • 15% through basement walls and the foundation footings;
  • 11% through the roof.

Poor insulation may also be responsible for a host of other problems such as cold floors and walls, condensation at the wall base and even traces of mold. Insulating your house therefore can make all the difference.

Learn more about insulating the foundations and insulating the roof.

Insulation procedures and materials

There are various types of insulating materials: rigid foam panels, fibreglass batts, loose cellulose fibre, injected and foam insulation. To be effective, the insulating material should:

  • uniformly fill the space to be insulated;
  • be resistant to heat transfer;
  • be long-lasting;
  • resist humidity (in certain cases).

Its thermal resistance or R factor (RSI in the metric system) indicates an insulating material’s performance. The higher the R or RSI value, the more resistant it is to heat transfer and the better it works as insulation. However, regardless of the insulation material used, its installation must be flawless because its thermal resistance depends on how well it is installed. In addition to its thermal resistance (R) and the associated cost, the first and foremost consideration when selecting insulating material should be its destined use. For example, certain materials are not suitable for insulating a basement but are perfect for insulating an attic.

Is your house well insulated?

Do you have any construction or renovation plans? Here are a few important things to consider when you start:

  • Insulating your house from the basement to the attic will not only eliminate the problems of cold floors, condensation and mold, but will also reduce your heating costs.
  • Pay special attention to structural components during any construction or renovation to make sure that these are coated with an insulating material that is laid down in a continuous fashion over the entire surface.
  • Make sure that the insulation is installed in a continuous fashion so that it covers all the joints and seams such as the transitions between walls, ceilings and floors in contact with the outside air, the ground or an adjacent unheated space.

Insulation that has been well planned and installed during your construction or renovation project will make your house more comfortable and reduce your energy bill.

How should I insulate a concrete foundation wall?

The following text provides guidelines on insulating foundation walls , whether from both the inside or and the outside. 

Although it helps to improve the energy efficiency of the homehouse, insulating foundation walls from the inside does not benefit the thermal mass of concrete and also reduces the inside space (thickness of the insulation).


In addition, insulating or increasing insulation of a foundation wall from the inside increases the risk of freezing. If the ground is damp and the foundations are close to the frost line, it is best to leave a non-insulated space at the base of the wall so that the heat from the building can be transmitted to the underlying soil.

Nevertheless insulating from inside is well suited to existing homehouses that do not require any outdoor excavation work since this is a more accessible method, it is cheaper and feasible in any season.

It should be noted that only sealed and well-drained concrete foundations should be insulated from the inside. For this, it is important to check for any cracks that might be the source of water infiltration from the outside. Humidity caused by condensation during summer usually causes black stains at the base of the wall, while infiltration from the outside can be detected by the appearance of a white deposit (mineral salts) on the concrete surface.

If water infiltration is detected or if humidity problems cannot be resolved from inside, adjustments will need to be made from the outside. Where necessary, this may even be the perfect opportunity to work on the insulation from the outside.

Insulating from the inside

To insulate a foundation wall from the inside, the use of moisture-resistant insulation material is highly recommended. Rigid polystyrene insulation (type 3 or 4) is an example of the most commonly used material for this purpose. As this material is combustible, it must be coated with a fire retardant to comply with fireproofing requirements under the building code in effect. Mineral wool and fibreglass also give good results as long as the insulation is protected with a waterproof membrane.

The total thermal resistance of a foundation wall should be approximately RSI 3.0 (R-17) for the fully assembled structure. Several techniques and combinations of materials can achieve this level of insulation. Using 76mm (3 in) rigid extruded polystyrene insulation or 25mm (1 in) type 3 or 4 polystyrene combined with 89mm (3.5 in) mineral wool batts (wool R-12), installed between 2x4 in (5x10 cm) studs, are two of the most widely used techniques to achieve this objective.

Insulating from the outside

If the perimeter drain needs to be repaired, take advantage of the opportunity to insulate the foundations from the outside. Stone and concrete block foundations must be insulated from the outside. In addition, insulating from the outside also makes it possible to take full advantage of the thermal mass effect of the concrete, which should improve temperature control inside the homehouse.

After excavating the foundations down to the footings, it is suggested to use rigid polystyrene insulation (Type 4) of at least 76mm (3 in.) thick extended over the full height of the wall. The insulation must be protected from sunlight. The use of a waterproof membrane and premium granular backfill will keep the foundations dry.

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