Condensation in loft, trickle down chimney breast

NeilFawcett · 1 Jan 2014

I've noticed over the past few weeks a small amount of condensation in the loft. Enough so you can see some droplets of water hanging from the roof lining and some drops that have fallen off into the boarding below.

I've half put this down to the cold/damp conditions we've had recently meaning there's a lot of moisture around, but today I noticed a couple of small runs of water down the chimney breast (in the loft) from top to bottom.

These were not major, but you could clearly see the path of water down the length an they were damp to the touch implying there was still a trickly going down them.

With binoculars I looked at the roof area around the chimney and the very top (flagstone) tiles immediately next to the chimney look questionable, but it's hard to tell for sure!?

So, is all this down to a couple of broken/damaged tiles around the chimney do you think, allowing water under the tiles and into the loft space? Or am I fighting a couple of battles here?

JohnD · 1 Jan 2014

your loft needs better ventilation. Is the loft insulation blocking the eaves?

//www.diynot.com/forums/viewtopic.php?t=160032

Perry525 · 1 Jan 2014

The condensation in the loft, will be the result of water vapour rising from your home and condensing on the cold roof. This is normal.

Runs of water down the side of the chimney are almost certainly down to leaking flashing. It may be that old lead flashing has moved or cracked - it may be a broken tile; the only way to find out is to get up there, and have a closer look.

It is rare, to be sure, but there are very few chimneys about that have been built properly with a tray fitted just above the point where the chimney comes out of the roof. But, it would be unusual for a problem at the very top to result in a trickle of water, usually the whole chimney would turn into a damp sponge.

NeilFawcett · 1 Jan 2014

Perry525 said:
The condensation in the loft, will be the result of water vapour rising from your home and condensing on the cold roof. This is normal.

So a little bit of condensation in the loft - enough to form some patches of droplets with a few dripping down (nothing major) - is normal this time of year?

Coincidentally I've just lagged the cold water tank up there... Could that contribute in anyway? There was alot of condensation on the "blanket" that goes over the top of the lid for example!

Perry525 said:
Runs of water down the side of the chimney are almost certainly down to leaking flashing. It may be that old lead flashing has moved or cracked - it may be a broken tile; the only way to find out is to get up there, and have a closer look.

It is rare, to be sure, but there are very few chimneys about that have been built properly with a tray fitted just above the point where the chimney comes out of the roof. But, it would be unusual for a problem at the very top to result in a trickle of water, usually the whole chimney would turn into a damp sponge.

OK, I'll book someone to have a look...

NeilFawcett · 1 Jan 2014

JohnD said:
your loft needs better ventilation. Is the loft insulation blocking the eaves?

//www.diynot.com/forums/viewtopic.php?t=160032

There has been some work done up in the loft (downlighters in a room) which means insulation has been moved in places.

I've just been up there and ensured the insulation in a lot of areas is not touching the roof lining so air can travel to/from the eaves. Most was OK, but I did move/clear a half dozen or so areas.

The condensation is almost all on the north facing aspect of the roof, which I suppose gets the coldest!

Here's the chimney... The camera flash makes it look worse (wetter), but you can get the idea...

JohnD · 1 Jan 2014

that bit looks to me more like a flashing leak of rainwater than like condensation.

downlighters will funnel warm moist air into the loft.

if the downlighters are in a bathroom they will funnel up vast amounts of steam into the loft.

NeilFawcett · 1 Jan 2014

JohnD said:
that bit looks to me more like a flashing leak of rainwater than like condensation.

Absolutely! I'll get it looked at!

JohnD said:
downlighters will funnel warm moist air into the loft.

if the downlighters are in a bathroom they will funnel up vast amounts of steam into the loft.

They are LED (so less heat), with thermal caps, and insulation and/or boarding over them...

The two in the shower room, are full IP65 shower lights (with caps/insulation). There's no more damp on the lining of the loft roof in that area than others, and to be honest probably less if anything than one two obvious areas?!

So the question is:-
- Is a mild amount of condensation in the loft as descibed above (droplets forming on north side of roofs lining with a few drops falling down) to be expected on damn/cold spells like this?
- Could the damp entering the roof from around the chimney be causing (some of) it?
- Could the lagging I put around the cold water tank be playing a part? Well, it does keep the water warmer surely, so more will evapourate?

JohnD · 1 Jan 2014

some of it must be coming from the rainwater leak, but a loft should be cold and draughty. Cap any remain holes in your ceilings. Water vapour is lighter than air so it rises through the house (it will also penetrate plaster, more slowly)

Your cold water tank doubtless has a tight-fitting plastic lid, and the incoming water will be very cold in winter, so it will not be steaming. If you have a feed and expansion tank for your radiators, check that it has a tight lid and is not warm.

The purpose of the insulation on a cold-water tank is actually to prevent it getting warm on a sunny summers day which encourages bacterial growth and slime.

NeilFawcett · 2 Jan 2014

JohnD said:
some of it must be coming from the rainwater leak, but a loft should be cold and draughty. Cap any remain holes in your ceilings. Water vapour is lighter than air so it rises through the house (it will also penetrate plaster, more slowly)

Your cold water tank doubtless has a tight-fitting plastic lid, and the incoming water will be very cold in winter, so it will not be steaming. If you have a feed and expansion tank for your radiators, check that it has a tight lid and is not warm.

The purpose of the insulation on a cold-water tank is actually to prevent it getting warm on a sunny summers day which encourages bacterial growth and slime.

The cold water tank has a round sheet of marine ply over it.... If you lift it up there is always some water on the underside of it.

HERTS P&D · 2 Jan 2014

Also, you don't have enough insulation up there, min 300mm.

Andy

NeilFawcett · 2 Jan 2014

HERTSDRAINAGE2010 said:
Also, you don't have enough insulation up there, min 300mm.

Andy

Well the insulation hasn't changed, so I don't see how that might account for any perceived increase in condensation in the roof space?

The insulation is not 30cm deep, it's the old traditional insulation between the beams so probably 15cm or so? That said:-
1) A lot of it is boarded up over the insulation which must give additional insulation.
2) In some areas (not used) I've put another layer of 15cm insulation running in the opposite direction, or old flattened cardboard (metre square) moving boxes over the insulation.

The other thing that makes me believe our loft insulation does a reasonable job is that the snow on our roof always melts later than our neighbours etc

Again though, is some condensation - as described in the original post - to simply be expected in the loft? ie: There will always be some moisture in the air, so there will always be some condensation onto the roof lining etc under these sort of weather conditions?

ps: Two roofers booked for tomorrow and Sat to look at roof/chimney leak. I'm hoping this accounts for a lot of the additional condensation. ie: Moisture/water coming straight into the roof space/beams.

Perry525 · 2 Jan 2014

The roofs in our village are interesting. You can never tell if they are insulated or not. Mine are the last to loose our snow- but then, we have 8 inches of polyurethane and polystyrene in our ceilings.

A roof covered with snow, may have very good insulation, or little or no heating, it may be in the shade from trees, or a mountain.

A roof without snow, it may have slide off, blown off, may be in the sun, they may have their heating on, the snow may not have fallen there.

Interesting possibilities?

NeilFawcett · 2 Jan 2014

Perry525 said:
The roofs in our village are interesting. You can never tell if they are insulated or not. Mine are the last to loose our snow- but then, we have 8 inches of polyurethane and polystyrene in our ceilings.

A roof covered with snow, may have very good insulation, or little or no heating, it may be in the shade from trees, or a mountain.

A roof without snow, it may have slide off, blown off, may be in the sun, they may have their heating on, the snow may not have fallen there.

Interesting possibilities?

It's indeed hardly a scientific approach, but, in my case we're talking about a row of identical detached houses, with identical roofs. Again, hardly conclusive, but an interesting indication I suspect.

We have I recon a good 4-6 inches of old style insulation, and than in a lot of areas, there's a further 4-6 inches of insulation, or 1-2cm boarding, or double sheets of cardboard ontop.

Over our LED downlights, there's thermal caps, which have a small 1inch share hole in the top to prevent over heating, but these then all have insulation or boarding over them.

Our two extractor fans upstairs both even have fans with sprung flaps incorporated to help prevent drafts.

I'd be interested in getting the roof insulated further, but as it's a low pitched roof I suspect it would be a nightmare to board it raised up on a false raised platform above the new insulation... etc...

Anyway... we digress from the condensation

Perry525 · 2 Jan 2014

NeilFawcett said:
JohnD said:

that bit looks to me more like a flashing leak of rainwater than like condensation.

Click to expand...

Absolutely! I'll get it looked at!

JohnD said:

downlighters will funnel warm moist air into the loft.

if the downlighters are in a bathroom they will funnel up vast amounts of steam into the loft.

Click to expand...

They are LED (so less heat), with thermal caps, and insulation and/or boarding over them...

The two in the shower room, are full IP65 shower lights (with caps/insulation). There's no more damp on the lining of the loft roof in that area than others, and to be honest probably less if anything than one two obvious areas?!

When you cook, boil a kettle, wash, dry things, breath, sweat, have indoor plants, flowers, animals, fish -especially young children; these things all emit water vapour. The molecules of water vapour are very tiny, small enough to enter things that look solid, like wood, plasterboard, most things used in building. This water vapour moves around in the air between the molecules of air. Think of it like a box full of footballs, and in the large spaces are lots of tiny ball bearing that move about. Water vapour is programmed by nature to head for the nearest cold surface or area. A lot of it heads for the nearest cold window. Some makes its way into the roof, passing through gaps round the trap door, through the plasterboard ceilings and the holes in your light cans.

So the question is:-
- Is a mild amount of condensation in the loft as descibed above (droplets forming on north side of roofs lining with a few drops falling down) to be expected on damn/cold spells like this?
- Could the damp entering the roof from around the chimney be causing (some of) it?
- Could the lagging I put around the cold water tank be playing a part? Well, it does keep the water warmer surely, so more will

NeilFawcett · 2 Jan 2014

Perry525 said:
When you cook, boil a kettle, wash, dry things, breath, sweat, have indoor plants, flowers, animals, fish -especially young children; these things all emit water vapour. The molecules of water vapour are very tiny, small enough to enter things that look solid, like wood, plasterboard, most things used in building. This water vapour moves around in the air between the molecules of air. Think of it like a box full of footballs, and in the large spaces are lots of tiny ball bearing that move about. Water vapour is programmed by nature to head for the nearest cold surface or area. A lot of it heads for the nearest cold window. Some makes its way into the roof, passing through gaps round the trap door, through the plasterboard ceilings and the holes in your light cans.

So you seem to be saying, some condensation in the house and loft is almost to be expected this time of year? ie: There will be some moisture in the air, and there will be cold surfaces with which to condense it.

In the case of the house, windows for example. In the case of my loft, my north face roof lining.

I wouldn't say the condensation is pouring off my lining. I would say it's in patches, and some of these patches are dripping a bit. For example, one of these patches is over our suit cases, and when I looked I could see 7-8 drops had fallen from the roof and were sitting on the cases.

There's other areas though where it's basically dry...

BUT, clearly water is evaporating from my cold water tank BECAUSE:-
1) I can see lots of water on the underside of the marine ply board over the top of it.
2) When I had a plastic insulation blanket over this board, it also got covered in a lot of condensation!?

I can't put a proper lid on the tank, as the plumbing goes into the tank from above/over the edge... I'd have to cut a small wedge out of the lid, just as has been done with the round marine ply cover...

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Condensation in loft, trickle down chimney breast

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