Secondary Glazing vs Triple Glazing

Noise Reduction

Triple glazing has three panes but typically uses an air gap of only 12–16mm between each pane. Secondary glazing reveal-fixed creates a 150–200mm cavity. Result: secondary glazing achieves 54dB noise reduction vs 33–37dB for triple glazing. Secondary glazing wins clearly for noise.

Thermal Performance

Triple glazing achieves U-values of 0.8–1.0 W/m²K vs secondary glazing at 1.5–1.8 W/m²K. Triple glazing is better for thermal performance when this is the sole priority.

Cost

Triple glazing costs typically £800–1,500+ per window installed. Secondary glazing costs £300–£500 per window. Secondary glazing is significantly more affordable.

Suitability for Period Properties

Triple glazing requires removing the original window. Secondary glazing preserves it. For listed buildings and conservation areas, secondary glazing is the only option.

Verdict

For noise reduction: secondary glazing wins. For thermal performance: triple glazing marginally ahead. For cost: secondary glazing wins. For period properties: secondary glazing is the only option.