HERBET Abel Sep 12, 2016:

It could also be : noise absportion

Tony M Sep 12, 2016:

@ BDF Whilst strictly speaking what you say is true, I feel totally convinced that here it is simply shorthand for a well-insulated roof (against sound).

This sort of usage is not uncommon with 'low-noise', in particular.

B D Finch Sep 12, 2016:

Generally, a "low noise roof" would mean a roof that produces little noise from e.g. expansion and contraction, effects of wind, rain, hail etc. Also, it would mean that any equipment installed on the roof should be low-noise. Here, there is some ambiguity, because of the minimal information provided, about whether it means this or an acoustically insulated roof, which is not the usual meaning of the term.