Condensation from Extractor fan
i am hoping someone can help with some advice, we have an issue of condensation dripping from the extractor fan in the ceiling of the En-suite, but not from the other extractor fan also in the ceiling of the downstairs toilet. both extractors vent on the Roof, and have rain covers in place, they vent up to the roof via 4'' grey tube, through the roof space and out. yet only the one in the En-Suite drips, this is the 3rd winter it has done it, does not do it through the summer months (which is understandable) it doesn't appear to be weather dependant, it can be misty or clear or cloudy and it will do it, then a couple of days later it wont drip.
i have turned on the extractor fan today and checked for a draft coming from the pipe in the loft which there does not appear to be a "leak" of air up the vent pipe.
the loft has insulation between the trusses which was laid in the 70's. there is a 2nd layer laid in a 90 degree angle to this, across the trusses, 1/3 of the loft has chipboard flooring with the older insulation underneath, it is boarded on the front 1/3 of the loft,
we do not turn the extractor fan on, there is a toilet, sink, bath, and shower head, the shower is not used, the bath is used once a week, basic the function of the ensuite is used for going to the toilet and cleaning teeth, on a daily basis. we do dry cloths indoors downstairs, on an airer which was monday, 5 days ago.
current internal upstairs temp is 21 degrees, outside temp is 9, has been dripping for 3 days constant.
i have possibly answered my own question in here but i dont know where! haha.
any ideas, suggestions or answer greatly recieved,