The old bathroom fan was a simple, low capacity unit, and I replaced it with a new squirrel cage model. The original vent piping was 3" that ran the width of the house to be vented inside the fascia. I replaced it with a shorter run of flexible, insulated (with a vapour barrier) vent tubing. I installed a new high capacity outside vent through the side wall above the attic insulation. This vent was not the dryer type but one with a integral anti-bird shroud. The amount of condensation in the bathroom after 2 shows is almost nil. When the weather got warmer water has been dripping during use from the fan housing. Where should the vapour barrier go? Over the fan housing, and under the insulation?
Answer:
You appear to have done nothing wrong except to vapour barrier the insulation over the vent duct. The duct itself is the vapour barrier and it even conforms to the principle of being on the warm side of insulation. You cannot over-insulate this duct and it needs no more vapour barrier than it provides for itself.
