What's the difference between soft-coat and hard-coat Low-E?

Soft-coat Low-E offers superior energy performance but requires more careful handling, while hard-coat Low-E is more durable but less energy efficient.

The main difference lies in how the Low-E coating is applied to the glass. Soft-coat Low-E (also called sputter-coated) is applied in a vacuum chamber using magnetron sputtering, creating an extremely thin metallic layer that's applied after the glass is manufactured. This process allows for multiple layers and precise control, resulting in better thermal performance with U-factors as low as 0.15-0.20.

Hard-coat Low-E (pyrolytic coating) is applied during the glass manufacturing process while the glass is still hot, essentially baking the coating into the glass surface. This creates a more durable coating that can withstand handling and cleaning better than soft-coat, but the energy performance is not quite as impressive, typically achieving U-factors around 0.25-0.35.

For Ottawa's Climate Zone 6 conditions, soft-coat Low-E is generally the better choice for maximum energy savings. Our harsh winters with temperatures dropping to -30°C mean every bit of thermal performance matters. Soft-coat Low-E can reduce heat loss by up to 50% compared to clear glass, while hard-coat typically reduces heat loss by about 30%.

In practical terms, quality window manufacturers protect soft-coat Low-E by placing it on interior surfaces of insulated glass units (typically surface 2 or 3 of a double-pane unit), so durability isn't usually a concern for homeowners. The coating is sealed between the glass panes where it won't be damaged during normal use.

Most ENERGY STAR certified windows in Canada use soft-coat Low-E to meet the strict U-factor requirements of 1.22 or lower. When replacing windows in Ottawa, choosing soft-coat Low-E windows can help qualify for Canada Greener Homes Grant rebates and will provide better long-term energy savings on your heating bills.

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