The Canadian ABC Rating of Windows
Every new window is identified with “ABC” ratings up to a maximum of A3B7C5. These measure how well the window will stand to air (A), water (B) and wind loads (C). The minimum rating for a Toronto-area home is A2B2C3.
A (wind) – The air-related ratings are measured by applying a 40 km-h wind across the window. The higher the number, the less leakage. An A1 reading shows the window will leak a little. A2 is better and an A3 reading is air-tight.
B (water) — The water-related rating shows how well the window will stand up to a driving rain, protecting the home from damaging water and mould. A window with a B7 rating can withstand a driving rain and 120 km/h wind.
C (wind loads) – The wind load rating demonstrates how will the window will stand up to a strong wind. A window with a C1 rating will begin to flex in the face of a gale force wind that is blowing at between 62 and 74 km/h. Most customers need at least a C2. But high-rise buildings might require windows with a C5 rating.