# Roof condensation



## Time Waster (16 Dec 2022)

Just been into loft for something. The plastic fake woodlap roof lining is covered in droplets. Obviously condensation due to cold weather (-12C Thursday at 630am) and us using more heating. Last winter we put an extra 200mm of rock wool on top of 1/3rd of the floorspace at one end up there. We moved in with the same at the opposite end so 2/3rds have extra 200mm or 400mm over half of this covered ends. Last year we didn't get this issue.

We have more junk up there but it's not right into the eaves. I don't think this is the issue but we're planning on a cull of stuff.

Is it likely to be the much colder weather conditions because nothing changed from last winter which didn't have an issue?

Solution? Do we need to do anything if it's an issue of this rare cold temperatures? Do we need more ventilation up there? 

It's a 70s house with upgraded insulation and a new roof put in when the solar panels were put up in 2016. The roof lining I thought was insulated but seems not. Being a new roof I assume it's going to be built with adequate ventilation. There's plastic fascia with what I believe are eaves vents, need to check fire ridge vents. If not enough should I get more put in? I'll check tomorrow in case there's blocked eaves. Perhaps the insulation is affecting insulation. 

What's the cheapest, what is the best or what is the easiest solution?


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## Slick (16 Dec 2022)

First thing I would check is, if you blocked the vents when the additional insulation went in.


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## GuyBoden (17 Dec 2022)

Your fake plastic is acting as a vapour barrier and changing the dew point, where condensation occurs. Check your timber Roofing Beams, Joists, Rafters and Trusses etc for water dripping on them.


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## lazybloke (18 Dec 2022)

I would also look at loft hatches, pipe penetrations and so on, see if you can reduce/prevent the warm/moisture-laden air going into the loft.


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## Time Waster (18 Dec 2022)

We don't remember last winter seeing this issue. Only changes have been new loft hatch which hasn't been fully sealed. A job on my list that has just gone up in priority. Also we put an extra layer of 200mm and a small section with 400mm extra rockwool. This mirrored the extra insulation at the other end of the loft space put in by previous owner. Both sets of insulation have been installed the same way. Since the original insulation didn't coincide with this issue and installation was the same the rockwool we put in shouldn't be the cause,

Around the boiler vent pipe it's dry. The roof under the solar panels seems less wet. Vents in ridge I can't see from inside, only the wooden ridge member. There's blocks of rockwool slab in the gaps at the edges of the loft floor. Can't see vents there but there must be because last winter there wasn't condensation. 

I like to think through things logically but I don't know enough to see the real issue. All I can think is to add vents up there and seal the hatch. I think I need to remove a panel of roof lining to see what's up there. 

BTW it was a new roof in 2016. The house is a run if 7 similar houses and the other houses have original roof from 1972


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## GuyBoden (19 Dec 2022)

https://www.nhbc.co.uk/binaries/con...-guide-to-condensation-in-your-roof-space.pdf
"The amount of insulation that’s required to meet modern standards greatly reduces the amount of heat that enters the roof space from the rooms below. This can increase the risk of condensation because the surfaces in the roof remain cold."

"*Most cases of condensation in roof spaces are temporary. It occurs when the weather is cold*, or when it changes between warm and cold, or when there is a big temperature drop between day and night.

Ventilation of the roof space is the usual solution for the condensation in the roof space. So, ensure all of the roof vents are not blocked. Your problem is probably due to the recent excessive cold weather.


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## Milkfloat (19 Dec 2022)

If you have rules everything else out it might be worthwhile checking to see if any bathroom vents are leaking into the loft. I once had a serious case of mould due to a vent that was straight into the loft after a contractor managed to dislodge a pipe.


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## Time Waster (19 Dec 2022)

Bathroom vent is straight through wall and comes on with lights. Boiler pipe is straight up and out the roof, intact. No other vents or ducts. 

My understanding is modern roofs have ridge vents and vents under the eaves to create airflow. Our eaves have plastic fascia and plastic tongue and groove looking underneath the eaves. No vents there that I can see. Ridge I don't remember seeing any raised ridge tile which indicates a vent. That's a big issue if there's no vents! 

Looking up there tonight it's better but one side and one end is still dripping. At the far end there's a vertical plywood board up to where the plastic slatted panels extend up the slope of the roof to the wooden ridge member. That board looks wet through which it didn't when the weather was still cold and the condensation was at its worst. Not sure what that means. 

Also there's two small bulges in the ceiling wallpaper in the room a third of the loft space from the bedroom end. They feel like there's water there. I had it in my old house due to blocked gutters forcing water under the bottom tiles. Not sure if that's happening here but it's near the window so could be. Not got high enough ladder to check the front gutters out. I'm not sure I want to go up a ladder up there. It's a bungalow with garage below. There's also no a good surface for a ladder imho. Plus I'm no good on ladders. I'm not sure it's the ladder that wobbles or my knees!


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## fossyant (19 Dec 2022)

Went in my detatched garage this morning and everything was dripping in water with the temperature change.



I shoved on the knackered dehumidifier


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## Slick (20 Dec 2022)

Time Waster said:


> Bathroom vent is straight through wall and comes on with lights. Boiler pipe is straight up and out the roof, intact. No other vents or ducts.
> 
> My understanding is modern roofs have ridge vents and vents under the eaves to create airflow. Our eaves have plastic fascia and plastic tongue and groove looking underneath the eaves. No vents there that I can see. Ridge I don't remember seeing any raised ridge tile which indicates a vent. That's a big issue if there's no vents!
> 
> ...



Have the original vents at the eaves been covered by the new plastic facia and soffit boards?


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## Mr Celine (20 Dec 2022)

If you're in the loft during daylight turn off any lights or torches you're using.

You should see light through the eaves vents.


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## CXRAndy (21 Dec 2022)

Ensure your not letting warm house air enter the cold roof void, seal your new loft hatch promptly. Check for all over warm air leaks and insulate over. If the roof has tar/bitumen type felt, check the eaves are clear all around. * Don't let the rockwool touch the felt or block the eave ventilation. *

If there is no eave ventilation or ridge ventilation, buy some pocket vents which slot into the felt. Fit them on the first overlap down by the eaves and near the top of the ridge. This should help with ventilation. 
https://www.bcprofiles.co.uk/produc...DoeFFXAJ_V9G5Rp0MaKGJvvMSIxdoBrMaAtG-EALw_wcB

A great tool to check for cold or warm break through is a thermal image camera Flir do smartphone versions. I used one on a roof insulation job on my newbuild to see if I'd properly insulated everywhere See heat bleeding through-additional insulation required


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