Soundproof windows for homes on busy roads: what really works

Homes along highways, airport roads and busy city streets deal with constant traffic, horns and construction noise. Windows are usually the weakest point in a wall for sound. The good news: the right windows can make a dramatic difference. Here's what actually works.

How sound gets in

• Through gaps. Air leaks carry sound. Even a small gap around a sash or frame undoes good glass.
• Through the glass. Thin single glass vibrates and passes sound straight through.
• Around the frame. Poorly sealed joints between the frame and the wall.

A useful rule of thumb: a reduction of about 10 decibels sounds roughly half as loud to most people. So every improvement counts.

What works, in order of importance

1. Airtight seals. Casement and tilt-and-turn windows press against gaskets when closed, so they usually block more noise than standard sliders. If you need a sliding door, a lift-and-slide system seals much tighter. See types of windows.
2. Laminated or acoustic laminated glass. The interlayer damps vibration. Acoustic grades are made specifically for this.
3. Double glazing with different pane thicknesses. Two panes of the same thickness resonate at the same frequency; using different thicknesses (for example a thicker laminated pane and a thinner one) blocks a wider range of sound.
4. Good installation. The gap between frame and wall must be properly filled and sealed.

A typical upgrade for a road-facing bedroom

• Casement or tilt-and-turn window instead of a slider.
• Double-glazed unit with one acoustic laminated pane.
• Frame fully sealed to the wall, inside and out.

For very loud locations, a second window on the inside of the opening (secondary glazing) with a wide air gap gives the biggest reduction of all.

Common mistakes

• Spending on thick glass but choosing a loose-fitting slider.
• Leaving gaps around the frame or under the sill.
• Forgetting trickle vents or AC sleeves, which can let noise in.
• Expecting total silence. Good windows make a room calm, but walls, doors and vents matter too.

Tell us where your home is and which rooms face the road, and we'll suggest the right window and glass for each. More about glass in our glass guide.