When planning a flat roof replacement in Toronto, many property owners focus on the membrane material—but insulation is just as important. Insulation plays a major role in your building’s energy efficiency, comfort, and long-term roof performance. In fact, overlooking insulation during a roof replacement can lead to higher utility bills and premature wear on your new system.
In most flat roofing systems, the insulation layer is installed directly beneath the membrane. Its primary job is to regulate indoor temperatures by reducing heat loss in the winter and limiting heat gain in the summer. In Toronto’s climate, where freezing winters and hot summers are the norm, a well-insulated flat roof helps maintain consistent indoor temperatures and reduce energy use.
During a flat roof replacement, you have the opportunity to upgrade from outdated or water-damaged insulation to modern, high-performance options. Rigid board insulation, such as polyisocyanurate (ISO), is commonly used for its high R-value per inch and moisture resistance. Some systems also incorporate tapered insulation, which improves drainage by creating a slope toward roof drains—helping prevent ponding water and membrane damage.
If your existing roof has wet or compressed insulation, it must be removed before the new membrane is installed. Wet insulation loses its thermal value and may lead to mold growth or roof deck deterioration. Leaving it in place can compromise the new roofing system and void your warranty.
Choosing the right insulation thickness is also important. While Ontario’s building code requires a minimum R-value for flat roofs, many property owners choose to exceed this standard for long-term energy savings. Thicker insulation may add to the upfront cost but pays off over time through reduced heating and cooling expenses.
Another benefit of upgrading insulation during flat roof replacement is that it improves the roof’s durability. Properly supported membranes last longer and are less prone to stress from temperature swings and foot traffic.
If you’re unsure whether your current insulation is sufficient, a professional roofer can inspect it during the tear-off process. They’ll check for moisture, gaps, and R-value performance, and recommend the best system based on your budget and building needs.
For expert advice and installation services, contact Flat Roof Repair Toronto. Their team offers complete flat roof replacement and repair and detailed commercial flat roof repair designed for energy-efficient, long-lasting performance in Toronto’s climate.