Moved in to a flat roofed 1960s house and there is a windowless bathroom with no existing moisture extraction. Planning to fit an extractor fan and duct vertically to a mushroom vent on the roof but want some advice about whether or not I need a condensate trap to stop any water dripping out of the fan. Don’t have attic space and a run for an overflow pipe for the condensation trap would be tricky. The only exposure of the vented moisture to the cold would be at the mushroom vent. Experience or advice would be appreciated to help me think this through.

I’ve not bothered. It’s a similar vertical run to a roof vent. Never noticed any drips but it’s over the shower so no big issue if there were.

As above fit it over the shower, gives the best extract and no issues with drips. Are you sure it has to go through the roof? Sounds like that could cause a lot more issues.

Thanks, the bathroom is in the middle of the house and there are two large RSJs either side in the roof which stops a run through the roof void to the outside walls. It’s a terrace so can’t vent to the either side without upsetting my new neighbours!

You can buy insulated ducting for this very reason

+1 insulate the duct properly, and keep the run short and straight. Have you got room for an inline fan – they tend to be more effective.

Mine’s a short run (above the shower through the attic space) and the builder said there was no need for a condensate trap – I’ve not had issues with drips.