Condensation in loft

[1900’s House]

I wondered if anyone can help me!
I recently moved into a 1900’s ish house which was really cold. I went in the attic and found minimal insulation, this was also picked up on the survey. So I set about adding another 200mm. I made sure I didn’t pack it too close to the eaves. Although there’s only a ventilation gap on one side which is about an inch and runs the full width of the roof. The other side the roof meets the wall and there’s no gap at all. I went into the loft the other day to check things were okay up there and was greeted with quite a lot of condensation on the what I think is breathable membrane and rafters. It’s not yet dripping onto the insulation. Now I can’t be sure whether this has coincided with this super cold weather or if it was there beforehand. The side with the ventilation and that gets the most sun seems to be completely dry. The side affected has the bathroom underneath which has spotlights with the fire resisting plastic things over and I have made sure these are pushed into place as tightly as I can get them. The other room under the affected part is an unused bedroom. I have added some foil insulation to the loft hatch and I have ordered a storm guard seal to add to it also.
I’ve read thread after thread about condensation in lofts and I’m not sure if I should hold fire with adding more ventilation into the weather warms up to see if things improve or if I should go ahead and add some regardless.
From my research the lap vents are pointless if you have a breathable membrane? I can’t add ventilation at the eaves on the other side, so am I left with the option of adding roof tile ventilation?
Sorry for the long winded message, I’m just losing my mind with what I should or shouldn’t be doing and want to avoid escalation of the problem. Any help would be massively appreciated!

 

[yorksbuilder]

Does the bathroom have an extractor fan venting to the outside of the house?

 

[1900’s House]

Yes it does

 

[noseall]

I wondered if anyone can help me!
I recently moved into a 1900’s ish house which was really cold. I went in the attic and found minimal insulation, this was also picked up on the survey. So I set about adding another 200mm. I made sure I didn’t pack it too close to the eaves. Although there’s only a ventilation gap on one side which is about an inch and runs the full width of the roof. The other side the roof meets the wall and there’s no gap at all. I went into the loft the other day to check things were okay up there and was greeted with quite a lot of condensation on the what I think is breathable membrane and rafters. It’s not yet dripping onto the insulation. Now I can’t be sure whether this has coincided with this super cold weather or if it was there beforehand. The side with the ventilation and that gets the most sun seems to be completely dry. The side affected has the bathroom underneath which has spotlights with the fire resisting plastic things over and I have made sure these are pushed into place as tightly as I can get them. The other room under the affected part is an unused bedroom. I have added some foil insulation to the loft hatch and I have ordered a storm guard seal to add to it also.
I’ve read thread after thread about condensation in lofts and I’m not sure if I should hold fire with adding more ventilation into the weather warms up to see if things improve or if I should go ahead and add some regardless.
From my research the lap vents are pointless if you have a breathable membrane? I can’t add ventilation at the eaves on the other side, so am I left with the option of adding roof tile ventilation?
Sorry for the long winded message, I’m just losing my mind with what I should or shouldn’t be doing and want to avoid escalation of the problem. Any help would be massively appreciated!

There are many things that need to be in place, in order to stave off condensation, when the really cold weather hits.

Such things like continuous eaves vents, vent trays, breathable membrane, vented ridge, vapour control, sealed loft hatches, mechanical extraction etc etc. Even then, if the weather is cold enough and the conditions are condensation rich, it can still occur.

I'd say, preventing the migration of the vapour, is the best but the most difficult challenge.

 

[1900’s House]

Okay thank you. I’ve seen people say that as long as this then dries out and only ever happens when it’s really cold it’s not something to worry about?
I was about to buy the vent trays but then read they aren’t useful with a breathable membrane only felt?

 

[noseall]

Okay thank you. I’ve seen people say that as long as this then dries out and only ever happens when it’s really cold it’s not something to worry about?
I was about to buy the vent trays but then read they aren’t useful with a breathable membrane only felt?

Do you have vented ridge or at least an in-out thing going on with the roof space?

 

[1900’s House]

There’s only the one ventilation point along that one side of the eaves. Nothing else the other side is completely sealed. No vent at the ridge. It has what I assume is a breathable membrane

 

[noseall]

There’s only the one ventilation point along that one side of the eaves. Nothing else the other side is completely sealed. No vent at the ridge. It has what I assume is a breathable membrane

We always supplement our BM with over-fascia vents (and vented ridge) etc....

trap1.jpg

• noseall
• 11 Nov 2024

Bolt2_LI

• noseall
• 27 Apr 2022

Bolt3_LI

• noseall
• 27 Apr 2022

Most breathable membranes on their own, won't cope with more extreme conditions i.e. very cold and vapour rich.

 

[1900’s House]

Do you think I I could add a roof tile vent to go along with what’s already in place? I’m thinking that a tile vent purely because I could probably install that myself? Would the lap vents work or is that pointless as it’s not felt?

 

[Harry Bloomfield]

I’m thinking that over ridge vent purely because I could probably install that myself?

No expert, but that would get my vote. Air needs to both be able to get in, and get back out, at the moment you only have a way for it to get in.

 

[1900’s House]

Thank you!

 

[JohnD]

I'm wondering about the eaves. Can you post some pics?

Also closeups of what you assume to be breathable membrane.

And the covers over the holes in the bathroom ceiling.

 

[1900’s House]

The first two are from the side where there is no gap at the eaves you can see the moisture on the membrane. Hopefully you can tell if that’s breathable or not? Then the last picture is from the other end where there is a gap at the eaves and the membrane is dry, rafters look like they’ve been wet at some point but are dry to touch.

 

[JohnD]

Thanks

Yes it looks like modern breathable.

The other eaves pic is very dark. Can you make out why there seems to be no gap?

If there is a soffit board it can be drilled.

 

[1900’s House]

I’ve been up on a ladder and there’s no gap at all on the rear of the house the brick meets roof? There are no soffits front or back?