Condensation and icicles forming in loft during cold weather

[TameRacingDriver]

Recently we had our loft space converted for storage, and while I am fairly sure this hasn't caused this issue - the fact we are now able to more easily access the loft has brought this issue to our attention.

Last week during the very cold snap, we went up there to put the xmas tree etc away, and noticed there was icicles formed on the felt on the roof: -





I'm pretty sure this isn't a good thing... anyway, the weather has warmed up today and there is a bit of a wind outside. When I spoke to a family member, he said to keep an eye on it and go up when there is a wind to see if there's any air flow into the loft which should help to dry it out.

I went up there this morning, and the icicles have now melted, leaving splash marks on the floor...



...and I can see that the wooden joists have become wet to the touch.



On the point about air flow, I was able to pull apart with my hands the felting, to reveal the tiles underneath, where I can see small gaps (as you would expect) and once I pulled these apart, I can feel the draught strongly, so it should be possible to improve air flow in here:



I'm assuming therefore I could either wedge something in there to keep it apart at various places in the loft to improve air flow, or better still, would I be best to get some vented roof tiles to improve the air flow in there?

Basically I just want the best course of action before this causes some very expensive damage in the longer term. Cheers

[Mont Blanc]

If nothing else, the ice formation shows that the insulation between the loft and the habitable space of your house is working very well indeed

Anyone who goes into their loft in cold weather and finds it warm up there is wasting an awful lot of money on heating...

[anotherbigspender]

I experienced similar issues the last time we had a cold snap. I did three things to resolve it. Firstly, I sealed round the loft hatch with foam tape to try and reduce the amount of warm air escaping in to the loft. Secondly, I fitted a load of felt lap vents to the locations where you have wedged your hand in the photo. One high and one low, staggered opposite each other on every other truss section. Finally, I fitted a load of soffit vents to the front and back of the property. I've not had the problem again.

Edited by anotherbigspender on Monday 13th January 10:45

Edited by anotherbigspender on Monday 13th January 10:48

[TameRacingDriver]

Mont Blanc said:

If nothing else, the ice formation shows that the insulation between the loft and the habitable space of your house is working very well indeed

Anyone who goes into their loft in cold weather and finds it warm up there is wasting an awful lot of money on heating...

yeah I don't think we have a problem with the insulation; the loft is really really cold when you go up there and we work and shower upstairs, it's usually in the low 20s up here but there's very little indication that much heat is getting up there at all.

@anotherbigspender (sorry the quoting seems to be cream crackered on here)
Thanks mate - the foam tape stuff, I guess that is either done on the edges of the hatch door or on the inside of loft? Those vent things seem inexpensive and definitely worth a try

[Cow Corner]

Is there any ventilation at eaves level, and if so is it free running (I.e. not blocked with insulation). Lap vents can be fitted, but check that any existing ventilation is working before you waste time.

As others have said, check the loft hatch is well sealed, as well as any other penetrations (down lights, extractor fans etc) that could provide a route for warm, moist air to enter the loft.

Ultimately, your loft is going to be cold in this weather and some degree of condensation is almost inevitable, but ventilation will help.

[anotherbigspender]

TameRacingDriver said:

@anotherbigspender (sorry the quoting seems to be cream crackered on here)
Thanks mate - the foam tape stuff, I guess that is either done on the edges of the hatch door or on the inside of loft? Those vent things seem inexpensive and definitely worth a try

My hatch doesn't fit very well and there was a visible gap between the frame and the hatch 'lid' itself when it was closed. I applied the tape to the rebate in the frame where the lid was supposed to sit which closed the gap and stopped (some of) the warm air escaping.

You'll know when you've put enough vents in because you can feel the air moving slightly when you are in the loft.

Also, depending on how old the house is, you may already have vents in the soffits. If that's the case, check that there are not being blocked by the insulation ringed in red below. Just make some gaps where the vents are if need be let the air flow.

Edited by anotherbigspender on Monday 13th January 10:59

[TameRacingDriver]

Cow Corner said:

Is there any ventilation at eaves level, and if so is it free running (I.e. not blocked with insulation). Lap vents can be fitted, but check that any existing ventilation is working before you waste time.

As others have said, check the loft hatch is well sealed, as well as any other penetrations (down lights, extractor fans etc) that could provide a route for warm, moist air to enter the loft.

Ultimately, your loft is going to be cold in this weather and some degree of condensation is almost inevitable, but ventilation will help.

There doesn't appear to be any ventilation at eaves level, I couldn't see any inside the loft, or when I poke my head out of the window, unless it's where the guttering is, where I can't see it? In the loft part, that area is taken up by insulation.

I understand that some condensation will be inevitable, I suppose it's just a matter of air flow so things can dry out, but obviously I'm trying to prevent much worse problems down the line.

@anotherbigspender - don't know why I can't quote your posts, but thanks I'll get up there this afternoon and pull back the insulation just to see if there is any ventilation lurking up there.

[zedx19]

Prolonged periods of cold weather will result in some amount of condensation, so long as it dries out quickly when the sun hits the roof, or weather warms I don't see anything to worry about. Yours looks like ours does during the really cold weather. Our back is south facing so the south facing roof will dry out within a few hours when the sun comes out, even if its still ice cold. The other side will often have small condensation droplets on it until the weather gets above freezing for a few days.

Few things I did which helped reduce condensation, as when we moved in 6 years back it was dripping in winter.

Fitted a few of the below, which helped airflow a lot. I also added thick solid insulation to the back of the hatch, plus foam strips around to reseal the hatch to the opening. I also found the extract pipe from the ensuite to the external wall was split, so all the humidity and moisture from the ensuite was going into the loft!


https://www.ebay.co.uk/itm/186823431199?chn=ps&amp...la-2361039923645&abcId=10027101&merchantid=6995734&gad_source=1&gclid=Cj0KCQiAkJO8BhCGARIsAMkswyiAUgCesLHZSYqLWKgrXOhD4La0z4OVkijc_l6Kl1sHZ9dTMhXy8zEaAoVYEALw_wcB

[Lotobear]

This is very common with the so called breathable underlays now used, which tend to be anything but (IME).

The lap vents are a good suggestion.

[TameRacingDriver]

zedx19 said:

Prolonged periods of cold weather will result in some amount of condensation, so long as it dries out quickly when the sun hits the roof, or weather warms I don't see anything to worry about. Yours looks like ours does during the really cold weather. Our back is south facing so the south facing roof will dry out within a few hours when the sun comes out, even if its still ice cold. The other side will often have small condensation droplets on it until the weather gets above freezing for a few days.

Few things I did which helped reduce condensation, as when we moved in 6 years back it was dripping in winter.

Fitted a few of the below, which helped airflow a lot. I also added thick solid insulation to the back of the hatch, plus foam strips around to reseal the hatch to the opening. I also found the extract pipe from the ensuite to the external wall was split, so all the humidity and moisture from the ensuite was going into the loft!


https://www.ebay.co.uk/itm/186823431199?chn=ps&amp...la-2361039923645&abcId=10027101&merchantid=6995734&gad_source=1&gclid=Cj0KCQiAkJO8BhCGARIsAMkswyiAUgCesLHZSYqLWKgrXOhD4La0z4OVkijc_l6Kl1sHZ9dTMhXy8zEaAoVYEALw_wcB

Yeah the pictures I took were of an East facing elevation, which seems to get the sun on a morning, most of the rest of the day, the sun moves around. The opposite elevation was, unsurprisingly, nowhere near as bad as this picture.

I will get up there this afternoon again to check the insulation in the gap as suggested above, and the link appears to be the same vents that were suggested above too, so I definitely think it's worth looking into.

I did wonder if there was an element of 'to be expected'. Assuming this has been going on the whole time, and not just since we had the loft done out, the house is currently 12 years old this year and so far it hasn't caused any real issues as far as I can tell.

[Lotobear]

...a loft I was in just last Thursday (you are not alone) - I advised the client to improve ventilation.

[TameRacingDriver]

Lotobear said:

...a loft I was in just last Thursday (you are not alone) - I advised the client to improve ventilation.

Oh wow, at least ours doesn't look anywhere near as bad as that, and I'd like to keep it that way

It appears those softfit vents are the way forward as an initial step, they are cheap enough and I can add plenty of them to try and improve the air flow. I guess these work by simply prising apart the felt like I did with my hands earlier?

[Lotobear]

TameRacingDriver said:

Lotobear said:

...a loft I was in just last Thursday (you are not alone) - I advised the client to improve ventilation.

Oh wow, at least ours doesn't look anywhere near as bad as that, and I'd like to keep it that way

It appears those softfit vents are the way forward as an initial step, they are cheap enough and I can add plenty of them to try and improve the air flow. I guess these work by simply prising apart the felt like I did with my hands earlier?

..with added frost

..a 10 year old roof on a 400 year old cottage - I would bet the previous covering, which would not have had any underlay, would never have suffered from condensation.

Yes, lap vents are a cheap and effective solution as another poster suggested.

[zedx19]

TameRacingDriver said:

Oh wow, at least ours doesn't look anywhere near as bad as that, and I'd like to keep it that way

It appears those softfit vents are the way forward as an initial step, they are cheap enough and I can add plenty of them to try and improve the air flow. I guess these work by simply prising apart the felt like I did with my hands earlier?

They just keep the lap open to allow airflow, you don't need to go mad with them. Again though I'd not worry too much if it doesn't cure it entirely as the extra airflow will just allow it to dry out quicker after condensation forms.

[TameRacingDriver]

Excellent, thanks for all your helps folks, I will get some of those vents ordered as a first measure, looks like even a total DIY idiot like me can do this

[Baldchap]

Difficult to tell from the photos but rockwool being applied all the way to the very edge can block any existing ventilation.

[TameRacingDriver]

Baldchap said:

Difficult to tell from the photos but rockwool being applied all the way to the very edge can block any existing ventilation.

Yep I going to check that this afternoon when I go back up there.

[OutInTheShed]

The water has to be coming from somewhere.

When it's damp and cold outside, I can get condensation on my aluminium loft ladder.
Same as you get dew on the car outside.
I have a 'pergola' with a roof on it, can't get more ventilated than that, it gets condensation on the underside of the roof at times.

If it's not super humid outdoors, then the moisture is probably coming from indoors, warm humid air below the ceiling promotes water vapour to pass through any holes, permeable surfaces etc.
As has been mentioned above, loft traps and downlights are prime suspects, but also any holes in the ceiling for lighting, plumbing etc.
Also check the state of any extractor fan ducting.
Some water vapour will always get through, you need enough ventilation to deal with that.
But no amount of vents at soffit level will beat excessive hot damp air rising from the living space.

[oyster]

I think you're all missing the likely number 1 cause of this.

Warm (relatively damp) air rising up when the loft hatch is open. I bet if you go up there and check the roof lining the moment you get up there, it's ok. The leave it 5-10 mins and the condensation will start.

[Lotobear]

Not necessarily - it's important to note that water vapour exerts vapour pressure and will pass through anything that is not entirely vapour impermeable (hance the use of vapour 'barriers'). Plaster and ordinary platerbaord and vapour permeable and water vapour will readily pass through it - ditto plasterboard joints and perimeter joints where it abuts walls.

Certainly downlights and poorly sealed loft hatches are ready paths but it is impossible in practice to fully exclude moisture vapour from a loft space in a conventionally built house (which is why we need ventilation)