uPVC double glazing typically has a U-value ranging from 1.1 to 1.5 W/m²K (lower U-value is better for insulation). A U-value of 1.0 or lower is considered good insulation. Energy-efficient double glazing will also have coatings like Low-E (Low Emissivity), which help improve energy efficiency.

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How to Know:

Ask your supplier or manufacturer for the U-value or energy performance rating based on the glass construction (e.g., the type of glass used, air gap, etc.).