Reducing Noise Through Windows

General Principles

The main factors in window noise reduction in order of importance are:

1. Glass Thickness

Thicker glass will give a better result. (Laminated glass is slightly better than solid glass of similar thickness as the laminated layer provides additional ‘Damping’)

2. Air Gap,

A secondary window system with a 100mm air gap will perform much better acoustically than a Insulated Glass Unit (IGU).

Thermally however the performance will be lower.

Having the glass thickness of the two panes vary by more than 50% improves the accoustic performance.

3. Sealing

Effective compression sealing around opening sashes, and sealing around the frame will prevent noise ‘getting around’ the window.

Noise Levels

Noise is measured in Decibels (dB).

The scale  is logarithmic, which means that each 10dB increase means the sound is twice as loud.

External Noise Levels

Conversation 65dB

Aircraft    65dB

Traffic    70 – 80dB

Construction  75dB (measured at your property boundary)

Recomended Internal Noise levels

Bedroom    30 – 35dB

Living Room    35 – 40dB

Noise Insulation Performance

Sometimes you will see performance quoted as a Sound Transmission Class (STC) others use Weighted Sound Reduction (Rw) values. Both units are essentially the same  and are equivalent to decibels,

Installing windows rated 30 Rw, or STC 30, will reduce an external 75dB noise  by 30dB, to an internal noise level of 45dB.

Approximate performance of various glazing  systems are:

TYPE THICKNESS mm STC / Rw dB
Single – Clear glass 3 30
Single – Clear glass 6 32
Single – Clear glass 10 36
Single – Laminate 6.4 33
Single – Laminate 7.5 34
Single – Laminate 10.3 37
Double – IGU 6  – 8mm air gap  –  4 34
Double – Secondary 6  – 100mm air gap –  4 46

You will need to talk to your proposed window suppliers to establish the exact performance and costs.