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Plumbing

Condensation in loft likely cause is bathroom ventilation fan ducting

Anonymous user 15/03/2024 - 2.37 PM

My question possibly requires help from someone with a combination of skills, knowledge and competency i.e. an electrician, a roofer and plumber? There is an electric ventilation fan fitted in the upper floor bathroom which is located over the bath and shower. The on/off switch is located outside of the bathroom. When the fan is switched on it will whirl for a minute or so before it becomes fully open (the surface has opening/closing shutters). We still get some amount of moisture when having had a hot bath or shower and although the fan will be switched on, the bathroom window is opened to help expel the condensation. The problem we have is and we noticed it some years now when going into the loft, that there would be moisture on some of the items (plastic would have droplets), some packages curled and felt damped, suitcases were mouldy, the membrane on the loft ceiling looked like it has damp markings etc. I have noticed in particular that the white plastic flexible hose/pipe looks splattered and once or twice it felt slightly damp and there were droplets on the loft floor (note, I don't know how the pipe/hose is attached to the fan, but the hose rises out of the loft floor and is taken up towards the roof, again, I don't know (or recall) how the hose is taken to the roof and to what it is connected externally e.g. is there a cowl kit, if any. First: what type of trade person do I need? seems like there is a combination of skills and knowledge involved? Second: would I be correct in thinking it is the hose in the loft which requires replacing including assessing whether the hose is connected to a cowl; if not have one? Third: would I be correct (after all the reading/info available) in thinking I should have the hose replaced with aluminium ducting - read this captures the steam and stop from becoming moisture/droplets and coming back down? Note, so far, there has been no evidence of water coming down and through the fan. Please advise me so that I get the right person to help and on the right materials for the task? Lastly: how would I know what is on the roof - will this person have to go and work on the roof, or will they be able to do the work from inside of the loft? I read that any pipes going up to the roof require a roof slate or lead which has to be sealed etc? Thank you SO very much! Mrs Lucas

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2 Answers

Anonymous user

Hi there, Condensation in the loft space can be related to a number of things, firstly the fan for the bathroom room needs to be vented outside, depending on the area available, the ducting should either be connected to a roof tile/slate vent, through a soffit or a hole drilled through the gable wall. Having a reliable vent which is vented to the outside will eliminate this as a cause. Another reason for condensation would be adequate air flow in the loft space, the loft space need to breathe, usually lofts are insulated to keep the warmth inside and the cold out, depending on the age of your roof which would explain a lot; Simply put your roof will need either breathable membrane vented through the fascia, soffits or ridge, or it will need to have roof tile/slate vents. My advice would be to check these to determine the problem, if it's the fan then you could simple change that yourself or ask an Electriacian, where if it's down to the roof not being able to breathe or you require the fan venting outside you will need a roofer. Hope this helps. Gavin Oscell Limited

Answered26 January 2018

Enventive Ltd (Trading as Envirovent S London and East Kent)

Rating: 4.9 out of 5

West Malling

Moisture in the loft is not necessarily coming from the fan, or at least not significantly in the wider scheme of things. Yes, the fan installation sounds poor and has a number of likely faults largely outlined in the previous answer. An important omission in that the ductwork is un-insulated - this may be what you mean by switching to metal ductwork as insulated duct is typically silver on the outside. However, the main cause of moisture in the loft is general humidity rising from the house. Yes, the loft is probably poorly ventilated but just putting in tile or soffit vents is no guarantee of an answer and it is not addressing the fundamental problem which is poor air quality in the house. I think a more holistic answer would be to provide a steady fresh air supply into the house. This will tackle the problem head on and help inside the house dramatically - which loft vents will not do.

Answered13 July 2020