When comparing ducting, don’t make the mistake of comparing ducting thickness as a measure of the effectiveness of the ducting insulation – it’s not the thickness of the ducting insulation that counts, it’s the quality of the insulation in the ducting.

As different ducting from different manufacturers use different insulation materials, the ‘Rt’ Rating is the only ‘apples for apples’ comparative measurement that you can use, to know which ducting is more effective at keeping the ‘air-conditioned air’ cool, while keeping the ‘hot roof air’ out.