Insulating flexible extractor ducting

26 Feb 2006
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Tyne and Wear
United Kingdom
Sorry if this is in the wrong place - not sure where it should go....
I have flexible ducting from a bathroom and en-suite to extractor fans and the to exterior walls.
It is recommended that the ducting is insulated to minimise 'in-house' condensation.

Can someone advise what I should use for the insulation please?

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Where does the ductwork run? If in the loft then simply run in beneath existing loft insulation.
Thanks Deluks
The duct currently runs across the joists on top of the insulation.
In theory I could put more insulation on the top but I'm also thinking I have to raise the ducting because it is currently below the level of the wall outlets so any condensing water will sit in the ducting (and flow back towards the fan).

Does anyone have an alternative proposal?

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If you insulate over it, then there will be no cold surface for air to condense on.

In any case there is little chance of condensation from a domestic ensuite set-up.

The warm moist air eventually diminishes and then the air temperature and humidity in the duct stabilizes to equal that outside the duct and so condensation is minute if at all, and any that does form evaporates naturally and does not sit there in pools of water
Dear all.

I'm going to uprate the fans and then I'll put loft insulation over the ductwork as it is. Pleased I don't have to raise it to the height of the wall outlet.

Thank you for the advice.

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