4.5.3 Measurement of sound insulation according to European standards
EN ISO 10140 series and EN ISO 717-1 (CEN 2010; CEN, 1997) apply to the testing and classification of the sound insulation of a window. The sound insulation found from the measurement
is expressed as Rw(C, Ctr) in dB.
The Rw value expresses the ability to reduce noise from outside to inside the building. Two correction factors (C and Ctr) are also found from the measurement.
The C factor should be used if the source of sound is speech, Ctr if the source of sound is rhythmic music or traffic noise.
A typical roof window with a standard construction of 2 layers of 4 mm glass, 16 mm cavity and 4 mm glass will attain an Rw of 32 dB.
If further sound insulation is needed, then windows with a pane construction of 2 layers with different glass thickness (4mm and 6 mm) will achieve a better sound insulation than a window with a standard glazing unit. Panes with 3 layer glass units with different distances between glass, and glass thickness, also perform better than the standard solution. Using a different gas filling will also have an effect – krypton gives better sound insulation. And finally, laminations are another way to achieve higher sound insulation of the glazing unit.
Example
Roof window with a glazing unit of 4 mm glass, 16 mm cavity with argon, and 4 mm glass
(4-16-4)