Roof Insulation Cost in Montreal

Roof insulation costs depend on the type of insulation, the method of installation, the amount of coverage needed, and whether the work is being done as part of a re-roofing project or as a standalone upgrade. For pitched roofs with accessible attic spaces, the most common insulation methods are blown-in cellulose or fiberglass, fiberglass batt installation, and spray polyurethane foam. Blown-in insulation is effective for filling existing attic cavities and can be installed over existing insulation to increase the total R-value. Spray foam provides both insulation and air sealing in a single application, making it particularly effective for stopping heat loss and preventing ice dams. For flat roofs, insulation is typically installed as rigid board above the roof deck during a membrane replacement. Polyisocyanurate (polyiso), extruded polystyrene (XPS), and expanded polystyrene (EPS) are the common rigid insulation materials used in flat roof assemblies. Tapered insulation systems can serve double duty by adding thermal resistance and creating the slope needed for proper drainage. The current Quebec building code specifies minimum insulation values for roof assemblies, and these requirements have increased over time. When a roof is being replaced, it is often required or strongly recommended to bring the insulation up to current code levels. This adds cost to the roofing project but delivers long-term energy savings and improved comfort. Ice dam prevention is one of the most important benefits of proper roof insulation in Quebec. Ice dams form when heat escaping through the roof melts snow on the upper portion of the roof, and the meltwater refreezes at the cold eaves. Adequate insulation and ventilation keep the roof surface cold and uniform, preventing this cycle. Based on Quebec market data for 2025-2026, here are the typical costs for roof insulation in Montreal: Blown-in cellulose insulation costs approximately $1 per square foot, making it one of the most affordable insulation options for attics with accessible space (Soumissions Quebec, 2026). A complete attic cellulose installation typically runs between $1,600 and $1,900 plus taxes for a standard residential home (Soumissions Quebec). Spray polyurethane foam (mousse giclee) costs between $3 and $5 per square foot for professional application (Soumissions Quebec, 2026). While more expensive than cellulose, spray foam provides superior air sealing and a higher R-value per inch, making it particularly effective for preventing ice dams. DIY spray foam kits range from $500 to $1,500, but professional application is recommended for roof insulation to ensure proper coverage and adhesion. Rigid insulation board for flat roof assemblies, typically polyisocyanurate (polyiso), XPS, or EPS, varies in cost depending on the thickness and R-value required to meet current Quebec building code. This insulation is usually priced as part of the overall membrane roofing project rather than separately. The current Quebec building code requires a minimum of R-41 for attic insulation in new construction and major renovations. Bringing an older home up to this standard often requires adding several inches of additional insulation over the existing material. Quebec homeowners may be eligible for the Hydro-Quebec LogisVert program, which offers rebates of up to $1,500 for roof and attic insulation and weatherization upgrades (Hydro-Quebec). This incentive can significantly offset the cost of an insulation project. Contact us to discuss insulation options for your roof. We assess your current insulation and recommend the most effective upgrade path.