Dripping attic following recent "improvements"

[AnthonyL]

Went up to get the Xmas tree down and dismayed to see the amount of water dripping down from the SW side.

It is a gable roofed bungalow, approx 8m width.

Recent changes:

1) Original Soffits & Fascias replaced with PVC

2) Added 200mm insulation mainly to the SW side (the side with the most problem)

3) Running the CH at a lower temperature

The roof already had has roof tile vents, and the attic was already boarded as shown in the photos.

I didn't add much insulation to the NE roof as that is mainly boarded. There is no sign of dripping on the side at first inspection.

Going by

may have been over-enthusiastic about using a rake to push the new insulation into the eaves on the SW side.

I do not recall ever having any such problem in the previous 6 winters. There was a bit of interstitial condensation showing on the sarking and rafters when the property was inspected at purchase hence the 6 roof tile vents which appeared to fix the problem.

I know the weather is a bit extreme at the moment and I would like any advice before I pull back the insulation on the SW roof.

[Theo]

By doing the works, did you perhaps block up any ventilation? For example rotten wooden soffits might have had cracks which you sealed up replacing with nice new PVC ones? I don't think pushing insulation into the soffits would cause problems of itself, only if there was soffit ventilation (deliberate or otherwise) which you have blocked.

Adding more insulation makes your roofspace colder, which makes condensation more of a problem. The solution to that is better roof ventilation. Maybe your tile vents aren't enough any more?

I'm guessing you have confirmed this is condensation, rather than say snowmelt coming in somehow? Does it feel 'muggy' up there?

Theo

[The Natural Philosopher]

Yup. I had water dripping off the windows here this morning. I opened the windows a crack and it all cleared. Ventilation is the antidote to humidity

Chances are some moisture laden inside air is leaking into the 'cold roof'..so fix that or improve soffit ventilation

[Tim Lamb]

During the conversion work on our timber frame chalet bungalow (built

1995) I was slightly surprised to discover a plastic membrane stapled to the underside of the loft timbers and above the plasterboard. As TNP says you don't want moisture laden warm air reaching a cold spot. Elsewhere the soffit includes a slotted ventilation strip. Where we have included original loft space for accommodation, I was careful to repeat the arrangement. Building control insisted that additional insulation should not fully block the air gap under the roofing felt. >

[AnthonyL]

I don't recall seeing any ventilation strips on casual viewing. Did the roofers miss something out? Are your strips obvious like this for instance?

[Andrew]

I had exactly the same. My semi has a 37 degree pitch roof and the house is North-South aligned so the north side of the roof never gets any sun at this time of year and that side collects condensation under the 1976 sarking felt which then freezes if the temperature goes below about -2C.

Then the next sunny day warms up the south side and all the ice melts and you can hear it dripping which is alarming in this weather because it sounds like a burst pipe dripping.

It only happens when we have a really cold spell immediately after a mild, muggy spell and the last one was 2008/9 and again 2009/10.

We had a *very* warm and wet November and all my temp+ humidity devices said it was 70percent humid inside the house. Now they say 45percent humid, so all that humid (effectively outside) air in the loft has dumped its water content on the sarking felt.

A few houses on this estate (built between 1973 and 1978) have had their marley modern tiles removed and the trusses re-covered with breathable membrane + new tile battens. Only two have gone the whole hog with new tiles as well.

Unless you have a warm roof structure this will happen every time we transition from warm mild damp weather to blocking high over Scandinavia and you have a cold roof that is ventilated with damp outside air.

[Andrew]

You can ventilate a cold roof all you like but if the air is carrying a lot of moisture as it was during our unusually warm November then a sudden change to -6 overnight is going to condense out that water inside the loft onto a convenient cold surface - the sarking felt.

[Tim Lamb]

In message [e-mail]>, AnthonyL [e-mail] writes

Yes. Not quite that fancy but similar rectangular slots.

[Robin]

If you have neither then the easiest thing to retrofit may be round soffit vents to give the equivalent of 10mm per meter (assuming no insulation in the loft over them). Eg

[AnthonyL]

I'm not usually in the attic every other day and I wasn't here till

2016. Of course by the time I get round to going up there and creating a bit of a gap the weather will have changed.

I've got a lot of stuff up in the loft which I don't want to get wet. Fortunately, as I haven't yet put everything where I want it, most is pushed up on the dry side whilst I've been waiting for it to be a bit warmer to spend an hour or two sorting it out.

[AnthonyL]

I'm pretty sure I have neither and the work was only done this year so I might go back to the roofers on this.

But ... I've only got the condensation dripping on the one side and that is the side I added the insulation and used a rake to push it into the edges. I think my first port of call is to retract it a bit so that I can at least see daylight.

It'll have to be pulled back anyway if the vents are added.

The screwfix items look ideal though, thanks, and being a bungalow it'll be a fairly easy job to put several in each side whoever does it.

[AlanC]

I am in a similar situation to you. I went into the attic to get the xmas tree and noticed condensation droplets hanging of the felt and wet patches on the boarded section and water marks on the insulation. The majority of the condensation is on the north'ish facing roof but there is some on the south'ish facing side. I havent noticed it in previous years but then I may just have not been paying attention!

We have had a few changes recently.

Summer 2021 - Roof "muck work" redone on the edges and ridge tiles re-laid. Fascias and soffits fitted along with new gutters. We didnt have soffits before this. The ends of the roof trusses projected out beyond the tiles and the external wall (I assume a decorative feature). There is a plastic vent between where the underside of the roof meets the external wall which has insect mesh on the outside part. I am sure there is a name for this setup but I dont know what it is.

Summer 2022 - Solar panels and house battery installed. The inverter and battery are in the loft space.

Oct 2022 - H/W converted to unvented. Cold water tank removed from the loft. I insulated where the tank had been now that we dont need to keep it warm.

There are several downlighters in the bathroom and ensuite. These are just covered by a metal box and insulation laid over the top of them.

The solar inverter and battery will produce some heat but it doesnt seem to be very much so I dont think this is an issue. Having the south'ish facing side of the roof covered in solar panels may mean that the loft doesnt warm up as much as it did before so this may be a contributing factor.

These are the things I think need to be looked at/addressed:

I have been looking at the soffits that were fitted and I cannot see any ventilation in them so I assume that is one of the problems. I'll need to speak to the company that fitted them. Maybe removing the soffits would be a better option rather than fitting vents as this might allow more airflow?

We are having the bathroom and ensuite refurbished in a couple of weeks so I was going to ask them about removing the plasterboard ceiling and replacing it with plasterboard and a vapour barrier or foil backed plasterboard. There is no vapour barrier between any of the ceilings upstairs and the loft at the moment. I guess it wasnt the done thing in 1989. We were also going to use a standard light fitting in these rooms rather than downlighters to minimise the risk of damp air getting into the loft.

Where our H/W was converted, this has left several holes in the ceiling between the airing cupboard and the loft (from pipes no longer needed). I need to fill these in.

I have orderd some of these:

they will help improve the ventilation!

I am also wondering if I need to fit some ridge vents (currently there arent any vents on the roof) or gable end vents. I may see if the changes above help first.

Alan

[Brian Gaff]

Yes I have one unused room upstairs and in order to save on heating, closed its door, the first time I went in I found the window frames frozen, and water on the window sill, Sealing a room up is never a good idea. What somebody seems not to realise is that warm air can hold a lot more moisture than cold air, and thus it was predictable in my case that the air as it cooled shed the water it carried. Brian

[Andrew]

Your solar PV's will massively reduce the amount of heat energy from the sun from warming your loft (and will also reduce the summer temperature of your loft) assuming they are on south/south-west facing roofs.

All the ventilation in the world won't prevent the problems that you, myself and others are having. It is the result of an extremely warm and humid November (so loft full of 'outside' air) followed by temperatures down to -6 or lower and minimal/zero wind.

In years gone by a warm/wet September would be followed by cold winds from the North West, but not below freezing. This would blow the humid air out of a (ventilated) loft or cold flat roof and replace it with much dryer air. Any subsequent really cold snap would be less likely to cause significant condensation.

This transition from Indian summer in september to much colder and dryer october doesn't seem to happen these days.

No need to remove existing PB. Just overlay with an extra layer of foil-backed PB (or just staple a piece of polythene sheet over existing ceiling and then add another layer of PB).

If you are really concerned with water vapour from the bathroom getting into the loft then don't have any downlighters.

[AlanC]

Ahh, good idea. I hadnt thought about just adding another layer. Thanks.

I had thought about adding a vapour barrier from the loft side by laying it over the joists, contouring it down to the back of the pasterboard (repeating over each joist) and then replacing the loft insulation. My concern with that method was that the joists are then on the warm side of the vapour barrier which might add a risk of them rotting?

We had our garage converted in 2014. The plasterboard that was fitted to the walls and ceiling had a vapour barrier behind it, basically sealing the whole room. The loft space above it has never had any signs of condensation. Given your weather statement above (which I am not disputing), I would have expected to see some condensation in the conversion loft. The same changes regarding fascias and soffits was also done on this part of the building too so I think it also has limited ventilation.

[Theo]

If the joists are the warm side, they are presumably warm (ie covered in insulation) which reduces condensation? If there's no insulation over the top of them, the vapour barrier would prevent condensation contacting the joists but would just condense on the vapour barrier instead.

The problem though is that you can't cover all of the joists, because the ends of them need to go into the walls etc. And that point might be where you get problems - if the joist is warm but the end goes into a cold wall, moisture can wick along the grain.

Theo

[Rod Speed]

Works fine for me to save heat because a sealed room would never freeze inside, it doesnt get cold enough for that.