Glossary · Insulation & windows
Low-e glass
Also called: low-E · low-emissivity glass · low-e coating · low-e glazing · low emissivity
Window glass with a thin, invisible metal coating that reflects heat, keeping more warmth in during winter and out in summer.
What it means
The coating lets most visible light through but reflects heat back toward its source. Versions for cold climates keep solar gain high (see SHGC) to capture free heat, while solar-control versions keep it low to reduce cooling loads. Low-e is usually combined with double or triple glazing and an argon or krypton gas fill.
Why it matters in an audit
It's a main reason modern windows have much lower U-factors than old ones, and it reduces condensation on the inside pane in winter.
Typical numbers
Reference values with their sources. Your energy advisor’s report gives the figure for your own house.
| What | Value | Source |
|---|---|---|
| Effect (NRCan) | Can reduce winter heat loss and summer heat gain by up to 50% | natural-resources.canada.ca ↗ |
| Highest indoor humidity before window condensation at −20°C outside, 21°C inside (NRCan) | Double-glazed 34%; double-glazed low-e 50%; triple-glazed low-e 67% | natural-resources.canada.ca ↗ |