Very Bad Loft Condensation - ideas on how to solve
Discussion
So, it got cold; my annual soaking wet loft problem has returned.
When the temperature drops, one side of my roof, which faces north-west, gets severe condensation, which drips constantly and makes the insulation and stuff in the loft wet.
The roof covering is about 15 years old, the tiles in very good condition and it apparently has a non breathable roof membrane.
There is zero eaves ventilation, due to the construction of the roof and fascias there is no way air could get in. I have six roof tile vents, midway up the roof, three each side. Its a random rubble stone walled house, former chimneys both ends.
The humidity in the house is now under control and is normally at 50%. The shower is vented directly out to a roof tile vent and the flexible duct is covered in insulation.
Everytime this happens I've got to put a dehumidifier up there to dry it out.
How do I solve this?
Reduce the source of moisture? I've solved a previous condensation mould problem and now have a well ventilated house and humidity readings of 50% throughout. I did think about a damp proof membrane running between and over the joists with the loft insulation on top.
More ventilation? This will require roofing work, probably at least a couple of hundred pounds. Eaves/Ridge/Gable Ends?
Forced ventilation? Install a small fan to draw air through, turning it on when there is a risk of this happening (automatically?) - seems a bit OTT but it would at least guarantee some air movement.
I've got to get this sorted this year!
When the temperature drops, one side of my roof, which faces north-west, gets severe condensation, which drips constantly and makes the insulation and stuff in the loft wet.
The roof covering is about 15 years old, the tiles in very good condition and it apparently has a non breathable roof membrane.
There is zero eaves ventilation, due to the construction of the roof and fascias there is no way air could get in. I have six roof tile vents, midway up the roof, three each side. Its a random rubble stone walled house, former chimneys both ends.
The humidity in the house is now under control and is normally at 50%. The shower is vented directly out to a roof tile vent and the flexible duct is covered in insulation.
Everytime this happens I've got to put a dehumidifier up there to dry it out.
How do I solve this?
Reduce the source of moisture? I've solved a previous condensation mould problem and now have a well ventilated house and humidity readings of 50% throughout. I did think about a damp proof membrane running between and over the joists with the loft insulation on top.
More ventilation? This will require roofing work, probably at least a couple of hundred pounds. Eaves/Ridge/Gable Ends?
Forced ventilation? Install a small fan to draw air through, turning it on when there is a risk of this happening (automatically?) - seems a bit OTT but it would at least guarantee some air movement.
I've got to get this sorted this year!
Edited by iamrcb on Sunday 18th December 21:18
Edited by iamrcb on Sunday 18th December 21:30
I'm suffering similar, though not as bad as yours it seems. I've already added eaves ventilation (which did improve it some), plus I cleared the area below the condensation to help with air flow. I only get this issue in one quarter of my loft which is a North facing area and unfortunately the area above the bathroom. My latest course of action is to replace the 10 downlights in the bathroom as they allow moisture to rise into the loft above. I've just bought some IP44 rated ones that are completely sealed, but I don't need these in all positions, so I'm going to order some suggested in another thread I started recently that are air tight (even tilting lights). I hope to do this over the Christmas break as llike you I want to sort the problem out.
When getting the decorations down today I also had a look at my loft hatch and realised that this is far from air tight, so even if the bathroom door is opened after use to help disipate the moisture, it will pass up into the loft via the hatch, as would any moisture from the rest of the house. I'm going to change the loft catch from the type you push up to unlock, to one that you turn 180 degrees to open, then I can add a seal all the way round the hatch to make it airtight when it is closed.
Might be worth looking at your hatch and any downlights: I bought some fire rated ones from Screfix this week and found that they weren't airtight: I understand they work by some material expanding in the case of a fire, but that doesn't help stop the moisture issue, so I returned them to buy the ones from this link:
http://www.tlc-direct.co.uk/Type/_Downlights.Mains...
When getting the decorations down today I also had a look at my loft hatch and realised that this is far from air tight, so even if the bathroom door is opened after use to help disipate the moisture, it will pass up into the loft via the hatch, as would any moisture from the rest of the house. I'm going to change the loft catch from the type you push up to unlock, to one that you turn 180 degrees to open, then I can add a seal all the way round the hatch to make it airtight when it is closed.
Might be worth looking at your hatch and any downlights: I bought some fire rated ones from Screfix this week and found that they weren't airtight: I understand they work by some material expanding in the case of a fire, but that doesn't help stop the moisture issue, so I returned them to buy the ones from this link:
http://www.tlc-direct.co.uk/Type/_Downlights.Mains...
williamp said:
I believe its due to lack of through-flow of car. You say you have vents, but do they allow a flow of air? Static air will cause condensation as it will warm up, and condensate when it touches the cold tiles. having the air cold, with good insulation will stop this
The 6 x 80mm diameter vents are all obscured by a close-by purlin so they are not ideal. Generally the wind blows up the valley where I live, so the airflow from the front to back of the house is probably not as much.I have around 200mm of the foil wrapped space blanket stuff. The loft is always pretty cold.
OldSkoolRS said:
I'm suffering similar, though not as bad as yours it seems. I've already added eaves ventilation (which did improve it some), plus I cleared the area below the condensation to help with air flow. I only get this issue in one quarter of my loft which is a North facing area and unfortunately the area above the bathroom. My latest course of action is to replace the 10 downlights in the bathroom as they allow moisture to rise into the loft above. I've just bought some IP44 rated ones that are completely sealed, but I don't need these in all positions, so I'm going to order some suggested in another thread I started recently that are air tight (even tilting lights). I hope to do this over the Christmas break as llike you I want to sort the problem out.
When getting the decorations down today I also had a look at my loft hatch and realised that this is far from air tight, so even if the bathroom door is opened after use to help disipate the moisture, it will pass up into the loft via the hatch, as would any moisture from the rest of the house. I'm going to change the loft catch from the type you push up to unlock, to one that you turn 180 degrees to open, then I can add a seal all the way round the hatch to make it airtight when it is closed.
Might be worth looking at your hatch and any downlights: I bought some fire rated ones from Screfix this week and found that they weren't airtight: I understand they work by some material expanding in the case of a fire, but that doesn't help stop the moisture issue, so I returned them to buy the ones from this link:
http://www.tlc-direct.co.uk/Type/_Downlights.Mains...
I've just got "normal" lights, plastic jobbies. I did put some rubber seal around the loft hatch, although I can't imagine that it needs to be air tight considering the scale of the problemWhen getting the decorations down today I also had a look at my loft hatch and realised that this is far from air tight, so even if the bathroom door is opened after use to help disipate the moisture, it will pass up into the loft via the hatch, as would any moisture from the rest of the house. I'm going to change the loft catch from the type you push up to unlock, to one that you turn 180 degrees to open, then I can add a seal all the way round the hatch to make it airtight when it is closed.
Might be worth looking at your hatch and any downlights: I bought some fire rated ones from Screfix this week and found that they weren't airtight: I understand they work by some material expanding in the case of a fire, but that doesn't help stop the moisture issue, so I returned them to buy the ones from this link:
http://www.tlc-direct.co.uk/Type/_Downlights.Mains...
Could you not rig up an electric pedestal blower fan (not heated) and leave it on a "swivel" setting throughout the winter, power consumption would be minimal, and would force the "still" air around.......
Worth a try at least, I would have thought, as long as you could not hear the "hum" downstairs....
Worth a try at least, I would have thought, as long as you could not hear the "hum" downstairs....
Mine is only effected on the North facing corner, so perhaps it's related to this, though clutching at straws a bit. Probably more likely due to some different construction method/materials. I haven't had this issue in previous houses either, but didn't have downlighters and the lofts weren't so big and those houses weren't detached...not sure if this makes any difference though. There's another poster on here who lives just down the road from me and his house is similar and also suffers condesation, so maybe more to do with the way it's built?
Simpo Two said:
That wall bottom left - looks like stone - is it cavity? Just wondered if moisture is getting through from outside.
How about insulating and lining? That would help to keep cold away from warm.
Its a solid (random rubble) stone exterior wall with an old, blocked off chimney in it. I used to fill the gap between top of wall and underside of roof with insulation, but pulled it out to try and get some airflow going, although there is no way in which air from outside coukd get in, so I may put it back.How about insulating and lining? That would help to keep cold away from warm.
Insulating between the rafters and lining (i.e. warm roof) would be expensive as its a fairly big roof.
Edited by iamrcb on Sunday 18th December 22:21
I thought about the warm roof option (there are firms that will spray a kind of foam onto the back of the tiles/membrane), but I read that it can cause more issues than it solves: I can't remember off hand what they were though. Like you I've got quite a big area as it's 10 metres wide.
Glad to hear the problems in the house are now under control.
I would venture that you start by evaluating how much of a problem this actually is. There seems to be some minor staining to your timbers, you should check that no wet rot has taken hold (in my opinion unlikely). The only other problem I can think of is if it's causing staining to your ceiling? If there is no deterioration to the fabric of the building or visual problems then it isn't that big a problem. Many roof voids suffer from condensation but people don't tend to go up often enough to appreciate it. I've been in about 5000 but I guess I'm in a minority!
I would advise against covering the rafters, this can trap moisture and reduce airflow - ideal for rot to develop and you won't see it.
Improving ventilation, forced or fixed, would probably help but you should balance the limited extent of the problem against the cost/hassle.
I would venture that you start by evaluating how much of a problem this actually is. There seems to be some minor staining to your timbers, you should check that no wet rot has taken hold (in my opinion unlikely). The only other problem I can think of is if it's causing staining to your ceiling? If there is no deterioration to the fabric of the building or visual problems then it isn't that big a problem. Many roof voids suffer from condensation but people don't tend to go up often enough to appreciate it. I've been in about 5000 but I guess I'm in a minority!
I would advise against covering the rafters, this can trap moisture and reduce airflow - ideal for rot to develop and you won't see it.
Improving ventilation, forced or fixed, would probably help but you should balance the limited extent of the problem against the cost/hassle.
OldSkoolRS said:
(there are firms that will spray a kind of foam onto the back of the tiles/membrane), but I read that it can cause more issues than it solves
Yes, it's criminal IMHO. Any moisture is trapped against the timbers, perfect conditions for rot. Rather like wrapping a bandage over a septic wound.C Lee Farquar said:
OldSkoolRS said:
(there are firms that will spray a kind of foam onto the back of the tiles/membrane), but I read that it can cause more issues than it solves
Yes, it's criminal IMHO. Any moisture is trapped against the timbers, perfect conditions for rot. Rather like wrapping a bandage over a septic wound.TooLateForAName said:
That felt looks quite tight?
I slipped lengths of plastic pipe between the layers of felt - that helped the ventilation quite a bit.
Too tight? Is it supposed to be loose? I didn't think so.I slipped lengths of plastic pipe between the layers of felt - that helped the ventilation quite a bit.
I will give the small diameter plastic pipe thing a go on one part of the loft to see if it makes a difference
This problem happens without fail every time it gets very cold outside.
I was surprised to read the comment about leaving this problem be. It just doesn't seem right. My ceilings don't get stained and my insulation is covered in plastic so it doesn't get sodden. I'd be much happier if it didn't happen.
How long have you lived in the house and how long have you had this problem?
My last house develop loft condensation, I had just about every suggestion thrown at me, such as needing air bricks in the gables ends (a useful sugestion for a mid terrace), more insulation, etc.
I sat down and thought about the problem, bearing in mind the house was 13 years old at the time and had never been a problem before, suggesting somethng had changed. The ventilation on this particular house was soffit vents front and rear, so the air flowed through the roof.
Thinking about what could have changed in the last year, I realised the then girlfriend had moved in, which resulted in a lot of stuff going in boxes in the loft.
These boxes were stacked sideways across the centre section of the loft from one side to the other. I'd blocked the air flow off. A damn good clearout and rearrange the remaining boxes against the side walls solved the problem.
My last house develop loft condensation, I had just about every suggestion thrown at me, such as needing air bricks in the gables ends (a useful sugestion for a mid terrace), more insulation, etc.
I sat down and thought about the problem, bearing in mind the house was 13 years old at the time and had never been a problem before, suggesting somethng had changed. The ventilation on this particular house was soffit vents front and rear, so the air flowed through the roof.
Thinking about what could have changed in the last year, I realised the then girlfriend had moved in, which resulted in a lot of stuff going in boxes in the loft.
These boxes were stacked sideways across the centre section of the loft from one side to the other. I'd blocked the air flow off. A damn good clearout and rearrange the remaining boxes against the side walls solved the problem.
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