Low-E Glass Explained: Is It Worth the Extra Cost?

Low-E (low emissivity) glass has a microscopically thin metallic coating that reflects infrared heat while allowing visible light to pass through. It's one of the most effective ways to improve a building's thermal performance.

How It Works A standard clear glass pane has an emissivity of about 0.84 — meaning it absorbs and re-emits 84% of infrared energy. A Low-E coating reduces this to 0.10–0.20, effectively reflecting most radiant heat back toward its source.

In winter, this means heat from inside the building is reflected back indoors. In summer, solar heat is reflected away from the interior. The result is a more comfortable building with lower heating and cooling costs.

Types of Low-E Coatings • Hard coat (pyrolytic): Applied during manufacturing while the glass is still hot. It's durable and can be used in single-glazed applications, but has slightly lower performance. • Soft coat (sputtered): Applied in a vacuum chamber after manufacturing. It offers superior performance but must be sealed within a double-glazed unit to protect the coating.

When to Recommend Low-E • Double glazed windows and doors (especially south and west-facing) • Replacement windows where thermal performance matters • Commercial projects targeting energy star ratings • Any application where the customer wants to reduce energy bills

Cost vs. Benefit Low-E glass typically adds 15–25% to the glass cost compared to standard clear. However, in double-glazed units, the percentage increase on the total unit cost is smaller. For most residential and commercial applications, the energy savings pay back the extra cost within 3–7 years.

Weight Impact Low-E coatings add negligible weight — less than 0.01 kg/m². For calculation purposes, treat Low-E glass the same as uncoated glass of the same thickness.