Condensation in loft.

gutovicky

Thank you grumbler, Co1umbofan and Norman_Castle for those encouraging comments about my soggy rafters.
I can now switch from 'anxious' to 'optimistic'    ...............this site is so good for my mental health!!

But I won't be complacent; grumbler, I DO aim to take steps to reduce humidity & improve ventilation in the loft.

Yes, Co1umbofan - I believe (& hope) this was quite an EXCEPTIONAL cold snap. 
This is my 6th winter in this town & in this bungalow, and I've never ever before felt the need to leave the CH on CONTINUOUS (for fear of pipework freezing).  
I realise that the fact that I left the CH on CONTIUOUS during the recent extreme cold/still period must have contributed to (or caused) the huge level of condensation in my loft - but how do other people ensure that pipework in the loft does not freeze?

Norman_Castle, you've touched upon another area of debate; the relative performance of old, bituminous felt vs newer, breathable membranes - in terms of reducing condensation...     I think I've read that some believe there is NOT that much difference(?).

You suggest that because your roof has a West-facing side & an East-facing side, the two sides of your roof receive the same amount of sun       ....I'm not so sure about that at this time of year....
My bungalow has the same orientation, and I have old-style, bituminous felt under the tiles THROUGHOUT the loft.  I have seen on several occasions recently that the West-facing side of the loft can have a lot of condensation, whilst the East-facing side has practically none.
I have put this down to the variation in strength of sunlight through the day.  The East-side benefits from any early morning sun (when the temp can be its lowest in fact).  By the time the sun moves round to the other side of the building, the day is duller and already getting dark.  Hence, the West facing side of my loft stays relatively (& significantly) colder - and receives the Lion's-share of the condensation.        ......What do you think?

Cheers, Vicky
 
  

grumbler

gutovicky said:

I realise that the fact that I left the CH on CONTIUOUS during the recent extreme cold/still period must have contributed to (or caused) the huge level of condensation in my loft

I don't see how this could have contributed.

- but how do other people ensure that pipework in the loft does not freeze?

They protect pipes with special pipe insulation and cover them with loft insulation.

gutovicky

Norman_Castle, I'm willing to bet that the East-facing side of your loft was the 'dry' side, and the West-facing side suffered the condensation - regardless of which felt was involved....
Am I right?
V

badatDIY

My rafters looked identical to yours and I'm not too concerned as a) treated wood is quite hardy and b) they've survived over 50 years and the previous owners must have produced as much moisture as we do and they're still solid so one week of damp shouldn't have destroyed them.

I also went back into the loft and refit the lap vents as I realised some of the felt overlaps were too long for the vent to do anything! Hoping to buy a few more in the new year when the price comes down

Norman_Castle

gutovicky said:

Norman_Castle, I'm willing to bet that the East-facing side of your loft was the 'dry' side, and the West-facing side suffered the condensation - regardless of which felt was involved....
Am I right?
V

You're right. It wasn't a scientific study, just an observation. I've also got north and south facing roofs. South facing is much drier.

gutovicky

grumbler....  you ask, how could having my CH on continuously in the extreme cold weather have contributed to the high level of loft condensation I experienced???

Well, because a portion of the heat will have travelled up through ceilings, one way or another, carrying moisture with it - just as we've being discussing.....

And tbh, I put the CH on to run continuously 'intending' to lose a portion of the extra heat as it traveled up into the loft. 
I know it's crazy, but I felt that if I didn't 'heat' my loft slightly like this, I stood a chance of having pipes up there freeze & burst.
That was my chief nightmare at the time.......  
[The huge amount of condensation produced was an unwelcome by-product of course].

My problem is:  I don't really know how 'at risk' my pipes in the loft were, or are. 
They are generally quite well-lagged (with the grey foam tubes of insulation), but there's always those odd little exposed & vulnerable bits of pipe - at spots where it's difficult to get to, or else at elbows/junctions... 
 
So grumbler, you're suggesting that I should lap 'Rockwall'-type insulation around and over all the insulated pipes, as extra protection against freezing?
Yes, I'm sure that would help, but would a quite loose-fit be OK?  and it would be tricky getting the roll up around the pipes to & from the water tanks for instance...  not all the pipework is low-lying & horizontal.
    
Sorry, I sound a bit clueless. 
It would be really useful to see some photos showing how other, more-prepared people have lagged their loft pipework.

Finally, & this is probably a stupid question:  how cold does it have to be outside before lagged pipes freeze/burst in an unheated loft?     ....was I possibly over-reacting to the -8 degs C temps? 

Thanks, Vicky 

gutovicky

Thank you badatDIY.  It's a relief to know that I probably haven't wrecked my roof!!!

However, I don't think the timber of my rafters (& the trusses generally) is treated timber - it doesn't look like it to me.
V.

Norman_Castle

gutovicky said:

Finally, & this is probably a stupid question:  how cold does it have to be outside before lagged pipes freeze/burst in an unheated loft?     ....was I possibly over-reacting to the -8 degs C temps? 

Last year I found a 3 foot long uninsulated cold water pipe which had remained unfrozen during the minus 10 weather about 5 years ago. This year my loft dropped to about 2 degrees with an outside temperature of about minus 7. I've got a single cold water pipe about 12 feet long above the insulation and insulated with cheap foam insulation which has never frozen.

All in my unheated loft with insulation above the ceiling keeping the heat in my home and out of the loft.

grumbler

gutovicky said:

grumbler....  you ask, how could having my CH on continuously in the extreme cold weather have contributed to the high level of loft condensation I experienced???

Well, because a portion of the heat will have travelled up through ceilings, one way or another, carrying moisture with it - just as we've being discussing.....

And tbh, I put the CH on to run continuously 'intending' to lose a portion of the extra heat as it traveled up into the loft. 
I know it's crazy, but I felt that if I didn't 'heat' my loft slightly like this, I stood a chance of having pipes up there freeze & burst.

Losing heat (because of poor loft insulation) and losing hot wet air flowing to the loft through gaps are different things.

Yes, pressure difference  increases with the temperature difference and so does the air flow if there are gaps, but 13C inside is a very low temperature by my standards.

As I said, you really need to deal with the air leaking to the loft in the first place. Without leaks, the more you heat the house the drier the loft is.

So grumbler, you're suggesting that I should lap 'Rockwall'-type insulation around and over all the insulated pipes, as extra protection against freezing?
Yes, I'm sure that would help, but would a quite loose-fit be OK?  and it would be tricky getting the roll up around the pipes to & from the water tanks for instance...  not all the pipework is low-lying & horizontal.
    
Sorry, I sound a bit clueless. 
It would be really useful to see some photos showing how other, more-prepared people have lagged their loft pipework.

Finally, & this is probably a stupid question:  how cold does it have to be outside before lagged pipes freeze/burst in an unheated loft?     ....was I possibly over-reacting to the -8 degs C temps? 

Modern requirements are about 30 cm of rockwool - this is much more than can be fit between the joists. So, the extra layer will cover horizontal pipes in the loft. Yes, other exposed pipes need better insulation - thicker lagging and better protection on bends. I'd use 25mm thick lagging and extra bandages of some insulation on bends, e.g. from long strips of foam packaging or underlay. And the better loft insulation, the colder the loft and the better insulation exposed pipes need.

ETA: my pipes (25mm thick lagging, the black bits cover a tap.)

rross11

Hi, it looks like you need require additional ventilation. From previous experience from our previous house, there was a design of vents which you can fit into the insulation to aid this. May have been covered above already. Hope this helps.