Hi

Our bedroom has a clip-lock steel roof and single gyprock ceiling. We are under a flight path for Sydney and the jets wake us at 6am on occasion.

Are are replacing the steel roof and adding insulation. The plan is foil backed insulation immediately under the new steel, and ceiling insulation on the ceiling.

The rafters are 200mm deep, and the steel at attached to batons on top of the rafters.

Currently, the ceiling has a layer of very old insulation batts that are now 50mm thick and very dense. They appear to be slag insulation.

The options are:

(a) Remove the existing insulation and install 200mm of light weight batts. My current preference is Quiet Stuff 200 - polyester 200mm deep; does not sag over time compared to fibreglass.
(b) Add light weight insulation on top of the existing batts. Here, the current preference is Quiet Stuff 100 - polyester 100mm deep. THis would leave a 50mm gap above the ceiling insulation before reaching the foil backed blanket under the steel; but then the batons also introduce a gap between the two insulation barriers.

From what I have read, density is important but that seems to be a property of barriers (like gyprock) rather than absorbers (insulation).
I have seen an archived post on this forum which points to Canadian data supporting light weight insulation in wall cavities, but this is a ceiling.

It is really difficult to find data. Anyone able to offer advice?

We also plan to double glaze a door 1.8m x 2.1m. The walls are brick veneer, so one might hope for rather improved sound performance once the weak points are addressed.


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