Performance Statement
The use of Tasman Insulation NZ Building Insulation Blanket (BIB) overlaid with a breather roofing underlay and in close contact with the underside of Dimond metal roofing can effectively reduce the surface impact noise from rainfall.
The noise reduction achieved has not been measured, but history of use suggests a noticeable reduction can be achieved. For the best results use either 75mm or 100mm BIB.
The effectiveness relies on correct installation whereby the supporting netting is stretched across the purlins to give a sag equivalent to one half of the blanket thickness. The BIB is consequently compressed by the roof sheeting over the total area.
Limitations of this system relate to the need for close contact between BIB and the roof underside and the consequences of a higher risk of corrosion from condensation or leakage moisture retained on the roof underside surface. Compression of the blanket will reduce thermal performance.
Other designed systems by acoustic engineers can be used such as:
- building up a layer of 17.5mm plywood and insulation blanket laid over the purlins
or
- using imported specialist products to deaden the noise when laid under the roof, such as Wavebar Soundbaffle. It does add extra dead weight into the roof system, i.e. 8kg/m2 , and is required to be fully sealed like a vapour barrier. For further information visit www.soundguard.com.au.
