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Autumn is now well established and the freshness of your veranda reminds you of the huge heating bills from the previous winters? Perhaps you should think about improving the insulation of this three-season living space, in order to enjoy increased comfort and make substantial energy savings, both in summer and during very cold winters.


A majority of verandas and solarium have an open floor whether it’s made of cement or wood. Unfortunately, this unheated space under the floor contributes to the circulation of cold and humid air, making the room very uncomfortable in winter, with the energy slippages that ensue.

To overcome this inconvenience, a solution is needed: to insulate the underside of the floor with a minimum of 5 inches of sprayed urethane, which will ensure a high-insulating value of R-30. In addition to acting as an air and vapour barrier, the urethane will perfectly seal the structure as well as all the interstices of the floor, guaranteeing an incomparable seal against cold, humidity and heat. (During the construction of a new building, the building code requires R-29.5 for an exposed floor. The application of 5 inches of urethane under the floor of a veranda or solarium meets this standard, which is adapted to the harshness of Quebec’s northern climate.)

IMPORTANT: In Quebec, the highest performing urethane can be applied down to minus 10 degrees Celsius. You must therefore plan to carry out your work between the months of April and December. During the winter, however, it is still possible to apply sprayed urethane during mild days.

Isolation Majeau has been specializing in basement insulation for more than 30 years
Visit the following pages to learn more about the services covered in this article:

– Urethane Insulation: Type 2 Sprayed Polyurethane

If your porch has a conventional sloped attic and is easy to access, you might also want to take a look at the current insulation. Is it in good condition and present in sufficient quantity? If you think it isn’t, we strongly advise you to add or replace the insulation of your attic.


– The veranda must have a perfect fit against the exterior wall of the house.

– Eliminate thermal bridges at all costs while the wall is open.

– The veranda and solarium must be properly insulated, preferably with sprayed urethane.

– The attic should also be properly insulated.

– Prefer quality windows with a sufficiently low U factor (heat transmission coefficient).

– Due to the thermal conductivity of glass, do not hesitate to compensate with more efficient walls insulated with 5 inches of sprayed urethane (for an R-30 value).

If you respect these basic principles, you will benefit from optimal thermal comfort in every season!

This article was originally published on July 1, 2022 by Marcel Lapierre