8. Acoustic Considerations

8.1 Windows are a major source of acoustic failure – because the wrong window type is used; and because the glass code AS1288 regularly provides for a glass thickness that does not provide adequately provide acoustic treatment. You must obtain a certified acoustic rating on windows prior to commencing. Refer also policy for windows and doors

8.2 As with doors, we need to minimise leakage – the movement of air through the window. So we want a POSITIVE seal for our operable windows. Louvered windows are useless form an acoustic perspective. Having a louvered window in a bedroom pointing at a main road is asking for trouble. Frameless glass doors are equally a waste of time for acoustic installations. Double hung, sliding and casement windows close onto rubber or similar seals to prevent leakage.

8.3 Glass thickness is next – 4.5mm glass offers low acoustic separation, 6mm glass improves, then 10mm is even better. The thicker the glass the more expensive the window. Laminated glass (two sheets glass joined together with a layer of adhesive sheet (available in many thicknesses) is more acoustic than a single thick layer of glass, and because it is joining multiple sheets of glass together, can be made in to a far greater over all thickness than a single sheet of glass (which is usually limited by cost and practicality to 12mm)

8.4 Where improved acoustic rating is required that cannot be achieved with a single glass layer (usually Rw 35 or less) – double glazed windows become necessary which are of course more expensive (can achieve Rw 36 to 45). If you have a required Rw of more than 35, you will need to look hard at the windows design!

8.5 Acoustic requirements should be defined in the acoustic specification/architects document

8.6 Procure written confirmation from the window subcontractor of the proposed system and certificate of compliance – get approval from the acoustic consultant before awarding the contract/starting drawings