Condensation in loft....................part 2

[beeman]

This is a very belated reply but could be relevant.I had noticed some condensation on the rafters in my bungalow roof structure and thought it was from moisture getting in at the ridge.This was only prevalent at the roof end nearest the tank.I even treated the ridge tiles externally with a waterproofer, with no success. I then covered the header tank in the attic, which had a glass fibre insulated loose fitting top to it, with a plastic sheet and tied it securely around the tank to 'close off' the tank top,putting the insulation covered lid on the top. Problem gone. Apparently evaporation from the tank water which condensed on the underside of the roofing felt. Just a thought worth contemplating,.Beeman.

[Markwj]

Sorry to resurrect an old thread but wondering if anyone has the same issue or how you resolved it. Our loft was boarded by the previous owners and looking up there today have found damp spots probably caused by condensation on the floor. The picture is the worst patch. I have been told roof vents would cure this but unsure how as this would only make the loft colder?

Thanks in advance

 

 

[cctransuk]

1 minute ago, Markwj said:

Sorry to resurrect an old thread but wondering if anyone has the same issue or how you resolved it. Our loft was boarded by the previous owners and looking up there today have found damp spots probably caused by condensation on the floor. The picture is the worst patch. I have been told roof vents would cure this but unsure how as this would only make the loft colder?

Thanks in advance

 

 

 

That is water that has condensed onto the interior face of the roofing felt and dripped off.

 

In cold weather the roofing felt gets very cold, and the warm air rising into the loft space is moist - hence condensation.

 

Insulation placed between and over the joists will prevent the warmth from the house entering the loft space - and save energy cost!

 

CJI.

[Markwj]

9 minutes ago, cctransuk said:

 

That is water that has condensed onto the interior face of the roofing felt and dripped off.

 

In cold weather the roofing felt gets very cold, and the warm air rising into the loft space is moist - hence condensation.

 

Insulation placed between and over the joists will prevent the warmth from the house entering the loft space - and save energy cost!

 

CJI.

Thanks there is insulation under the floorboards but wonder how effective it is, thank you for the advice

mark

[30801]

I had trouble with moisture getting into the loft via the bathroom ceiling. It was starting to rot out the loft boards. I replaced the ceiling mounted extractor fan with a larger one where the fan sits up in the loft. No more moisture in the loft and no more condensation running down the bathroom walls.

[Izzy]

I have lived in my house for nearly 45 years. It’s 1920’ built with brick cavity walls. The eaves are open and although it’s often been cold up there in winter always dry throughout all that time as has been the whole house. About 7 years back we had new windows along with dry cavity wall insulation and full loft insulation to reduce costs, which it did, roughly halving them.
 

Even though we have not changed in any way how we heat the place over the last 10 days we’ve had some condensation on the windows inside, a new experience for us. But the biggest shock was going up in the loft today to get the Xmas decs down. A damp atmosphere with condensation on the felt and dripping down on the stuff stored. The water tanks are fully insulated. Never ever had this before.

 

Can only assume it’s the particular weather conditions that have caused this. An extreme wet period late autumn followed by extreme cold with no drying wind. Can’t see what else we could do to prevent it. Quite bemused.

[cctransuk]

46 minutes ago, Markwj said:

Thanks there is insulation under the floorboards but wonder how effective it is, thank you for the advice

mark

 

The problem with boarding lofts is that modern insulation standards require insulation thicker than the joists.

 

If existing thick insulation is compressed when boarding the loft, it becomes far less effective.

 

CJI.

[rab]

One cause of loft condensation I believe is insulation

pushed right out to the eaves.

 

My understanding (and I'm happy to be corrected)

is that there should be a gap, to allow air to circulate.

 

[30801]

9 minutes ago, cctransuk said:

The problem with boarding lofts is that modern insulation standards require insulation thicker than the joists.

 

That's no bother. You just put the boards on legs thusly

[Andy Hayter]

But you really should not be boarding onto ceiling joists unless the boarding is only to allow storage of light items and very occasional footfall.  

[2E Sub Shed]

Situation I found in one house was that the extract fan exhausted directly into a void, in this case into space between ceiling and first floor, the builder did not bother to fit a outlet to a vent ! 

 

Builder who recently installed my kitchen, told me of a simmilr situation with a bathroom extractor fan exhausting in to roof space.

 

Edited December 17, 2022 by 2E Sub Shed
Add missed text

[cctransuk]

Just now, 2E Sub Shed said:

Situation I found in one house was that the extract fan exhausted directly into a void, in this case into space between ceiling and first floor, the builder did not bother to fit a outlet to a vent ! 

 

 

Builder? Bodger!

 

CJI.

[cctransuk]

40 minutes ago, 30801 said:

 

That's no bother. You just put the boards on legs thusly

 

Headroom clearance is usually a problem in lofts - raising the boarding to this extent would surely reduce it to an impractical extent?

 

CJI.

[2E Sub Shed]

Just now, cctransuk said:

 

Builder? Bodger!

 

CJI.

 

Fully signed off by Building Control (when Council run), also a few other contraventions, both previous owners including the one who had the extension built and the subsequent owner were listed in yellow pages as builders 🙂

 

Agree with comment (2" x 1" used to hold up a water tank)  

[30801]

16 minutes ago, cctransuk said:

Headroom clearance is usually a problem in lofts - raising the boarding to this extent would surely reduce it to an impractical extent?

 

Not my loft, but this is the arrangement we have for storage. If you were making a habitable room you wouldn't be using this stuff. Headroom in the middle is still more than plenty.

[Izzy]

2 hours ago, rab said:

One cause of loft condensation I believe is insulation

pushed right out to the eaves.

 

My understanding (and I'm happy to be corrected)

is that there should be a gap, to allow air to circulate.

 

Yes, there should be. Boxed in eaves should have ventilation fitted, to stop rot with wooden ones as well but also with the common plastic re-do’s. It’s the sign of a good tradesperson. In my open eaves there is a good 1” gap between the roof and the walls, well there was, I shall have to check in the spring that the insulation hasn’t somehow moved and blocked the airflow which seems increasingly likely.

[Phil Himsworth]

4 hours ago, Markwj said:

I have been told roof vents would cure this but unsure how as this would only make the loft colder?

The problem is not so much the fact that it is cold, but that warmer air from inside the house has been able to get to the cold bit and get stuck; it then cools and the water condenses out.

 

The two ways to fix it are to stop the warm air getting there in the first place -seal any gaps in the ceiling, make sure extractor fans vent properly - or make sure that if any warm air does get up there it can escape before it cools down inside. Roof vents do this; I fitted some in our loft last year, just lap vents that simply push between the felt strips, and the problem went away. Stopping the air getting up there in the first place is better, but realistically you can't seal every single gap so the latter method is still a good idea.

 

This problem often appears when improving the insulation between house and loft; with poor insulation the roof is warmer so damp air won't condense, but at the expense of losing heat through the roof much quicker.

 

[Phil Himsworth]

2 hours ago, 2E Sub Shed said:

Situation I found in one house was that the extract fan exhausted directly into a void, in this case into space between ceiling and first floor, the builder did not bother to fit a outlet to a vent ! 

The last two houses we've had have both had extractor fans venting into the eaves of the roof space but not outside. I wonder how many houses are like this without the occupants knowing about it; I bet it's a lot...

[Dave 46]

3 hours ago, 2E Sub Shed said:

 

<snip>

Builder who recently installed my kitchen, told me of a simmilr situation with a bathroom extractor fan exhausting in to roof space.

 

When I moved into my present house (1980) the previous owners had demolished a chimney, down to below the roof line.  The gas fire in the downstairs room would have vented into the (very poorly insulated) loft space if they hadn't blocked the flue with rubble.  As they were paranoid about draughts and had used masking tape to seal all the windows, the wife apparently used to complain of headaches.  I think she was rather lucky not to have suffered serious consequences.

 

Dave

 

[fulton]

As a house builder in a previous life, NHBC accredited, the problem is we are using spaces, mostly, never intended or designed to be used this way, unless you invest a lot of effort and or money to get insulation, vapour barriers and ventilation in the correct places, you will in these extreme weather events, get condensation problems, or worse, structural problems from overloading the roof structure. Particularly in our UK, mostly damp climate, there is always a need to balance between sealing everything up to save heat, against the need for ventilation to stop condensation, and tragically the recent death due to mould.

[billywhizz]

Just been up into the loft looking for book and found a lot of condensation dripping off the felt on the north facing side of the roof. Felt on the south facing half of the roof is pretty dry. Not noticed this before. The house was built in the late 70’s and the loft is insulated. The only section boarded is the centre section for storage purposes. There are air bricks in both gable walls. There are no water tanks up there or anything venting into the loft space. I guess it could be down to the current cold snap but concerned how much damp is up there. 
Any thoughts on what I could do to reduce the condensation?

Thanks in advance. Bill. 

[Andy Hayter]

To reduce the condensation in the loft, you have to do one of 2 things:

Increase the temperature in the loft - add heating which is probably going to be a waste of hard earned

or

reduce the water vapour in the loft - most sensibly by increasing ventilation up there or by installing a dehumidifier.

[billywhizz]

Thanks @Andy Hayterwill be up there this evening moving cardboard boxes from under the north facing roof (currently being dripped on to under the south facing side. While I am up there, I will check to make sure the air bricks are clear. 
Thanks again. 
Bill. 

[billywhizz]

Hi @Andy Hayter thanks for the advice. found a couple of things which I think could be causing the condensation. The holes is the air bricks were blocked with muck so cleaned them out. The insulation on the north facing side of the roof (where the condensation is dripping off the felt) was tucked into the eves? (Where the roof meets the top of the house wall) so I have pulled it back to create an air gap. Will check again in a few days to see if there is an improvement. 

[Andy Hayter]

I hope that works for you.