Condensation in Loft - Solutions

nico12

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Morning guys

In September I had my bathroom refitted and had a seperate shower cubicle put in.
the shower has an extractor fan in the cubicle roof then flexi duct up to another fan half way along a 6/7m stretch to the vent in the soffit / outside.
when I’ve been in there to sort Xmas decs the felt is quite wet (drips) and worried some of the joists are damp too. Never noticed this before.
I had some work done on the water tanks and noticed the central heating vented tank had the lid removed - I’ve replaced this - could this be contributing ?
I also have some spare rock wool that was used to insulate loft - can I use this to ‘ lag’ the flexi pipe - will it work ?
I already have vents in the Eves that seemed to be working up until the works ?
many advice appreciated- worried stuff will get damp unless I sort quickly
Also ( daft question ?) should I try and ‘ mop up’ the moisture that’s there now ? Fan?
any advice appreciated
 

satinet

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I would want the shower vented properly in to its own grill/vent. They kick out a huge amount of condensation. Think the Mrs in the shower for 30 minutes.

Yes I think the top being off the tank might contribute.

Fans only move stuff about. Best way to get rid of water is mopping it up followed by dehumidifier if there isn't good ventilation.

However you are saying the property has vented soffits or similar? What's the age of the property? Problem with older houses is that they don't have good loft ventilation. They were made before sealed Double glazed windows, central heating, power showers etc.

The problem is you seal the house with modern windows and insulation (emg cavity wall) and then kick out loads more humidity with showers etc in to a space that isn't well ventilated ( heat goes up). A modern loft will have usually all the soffits vented (or equivalent e.g last row of tiles sat on a plastic vent) and he ridges sat on plastic vents. This creates air flow .

I would look at the shower as the first culprit. Run it and go to the loft. Could just be a split pipe.
 

satinet

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Just to say if you have the shower venting through the loft in a long pipe you want an inline fan in the pipe. One of those square surface mounted jobs are not up to the task if its a decent shower and long pipe. Obviously you want vent to terminate outside and the pipe to be fully sealed.
 

Dave

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Are you sure it's an extractor fan in the cubicle roof, or is it just a grille connected to the flexi duct and then the inline fan?

Make sure that the initial length of duct from the 'grille' is higher than the rest and sloping down towards the fan and then the outlet.
Ensure the outlet is going into a grille in the soffit and not just exhausting into the back of the soffit expecting it to then ventilate outwards. If this is the case the warm, moist air might be sitting behind the soffit and being drawn back into the loft space.

The lid missing off the water tank won't have helped, especially if you've had the sun on the roof warming up the loft space.
 

nico12

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Thanks for the replies. The property is 1970’s.
I am having new soffits and fascias this week ( with hidden vents)
The shower has a fan directly above the unit ( ceiling) and another fastened ( quite large ) to a loft board.... then flex out to the soffit vent.
there is a slight rise from the initial fan to the ‘ 2nd’ one and then down slightly to the soffit exit.
I am also aware I need to clear the ‘ stuff’ better in the loft - piled around area. ( it’s quite a close space - crawl rather than stand)
I am going to insulate the loft hatch too ...some evidence of cobwebs / air at the back.
will the spare rockwool act as a decent insulation method if I wrap it loosely around the flexi pipe ( same stuff as tumble drier) ?
hoping a combo of all above will help?
I will make sure it’s going outside too ( good shout) - though god knows how 😊
I’ve had convector heater up there and dried some areas out. Think it’s only effecting some not all loft space
 

Dave

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Check to make sure you've no tears or leaks in the flexi pipe.
Insulating it won't make a difference as the heat loss from it won't be enough to cause condensation
 

satinet

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If it's venting to a soffit it could easily be just blowing back in to the loft space.

It's important to understand that you need to get rid of damp air through ventilation. If you evaporate damp in to the air in a sealed space you aren't getting rid of it. That's why dehumidifiers are better than heater at dealing with the aftermath of floods and leaks.

Hence I was saying that 1970s houses were built before houses were as well sealed/insulated as they are today and before things like showers running direct off boilers that can heat huge amounts of very hot water very quickly. They weren't as well ventilated in the loft because the rest of the house was more leaky it wasn't a problem.

Worth a read Why Loft Ventilation is so Important?
 

Sassenach

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When you say shower cubicle.. is it floor to ceiling, fully enclosed?

What makes up the shower ceiling, is it plastic from the shower cubicle or the bathroom plasterboard ceiling?

What lights have you got, if downlights, are they IP rated sufficiently, if not, they are not sealed and will let steam into loft.

You say you have an in-line fan, in the loft, along with a surface fan on the ceiling in bathroom, with 6/7 meter run of flexi duct running to the soffit.. Ideally these should all be 100mm, if it were me, I’d check that the duct is fixed to a grill on the soffit and not just laying there next to some slots in the soffit board. Otherwise, because of the length of run to the soffit, i would remove the ceiling fan in bathroom and replace with a 100mm grille, fix the in-line fan in loft, closer to bathroom, then get a vented roof tile with a 100mm duct connection, and use the flexi duct to connect it all up, with the theory that the hot air goes straight up and out.. 🤷🏻‍♂️
 

Dave

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That's how mine are set up at home ;)

But no lights in the shower cubicles
 

neil fallows

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Put your central heating on for a couple of hours then go and check your header tank. It should be cold but if the system is getting blocked with sludge it could be pumping over { hot water coming out of open vent in to tank) and this will fill the loft with steam and create problems. Its a happens frquently.
 
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