Condensation in my loft - not there before

[lizziecupcakes]

Hi all
We added loft insulation ourselves back in early December. I've checked the loft weekly for any signs of condensation - it's all been fine.
Last time I checked it was 6th Jan (one week ago - the temperature range that day was 2 - 12 degrees where I live).

However, about an hour ago I checked up there again, and there is condensation everywhere, and seems to appear in a patterned manner, like following the edges of the tiles on the roof.

I am quite worried.
We have a few ventilation tiles up there and it is quite cold up there compared to the rest of the house. We added vent laps too. We don't have eaves ventilation.

I've left the loft hatch open (it's in the bathroom, which is annoying) and the bathroom window open to try and encourage some air flow.

I don't know if this is just a one off because of the very cold freezing weekend we've just had (which is also not the normal January temperatures we see in SW London this time of year), but I wondered what you all thought?

 

[lizziecupcakes]

 

[Lacan07]

It might be something to do with the rise in temperature we've experienced in the last 12 hours. Have you had the heating turned up during this cold spell, more so than in December?

 

[lizziecupcakes]

Thank @Lacan07, and yes, we've definitely had the heating on much more in the past week compared to the whole of December. It wasn't on much overnight though, but it was warm in the house as I couldn't sleep very well last night. Whenever I would check on the loft, it would be very cold up there, but there was never any condensation before.

Our roofer is here today to fix some other issues, and he confirmed that we don't have eaves ventilation. I'm thinking about adding this, but don't know what this entails.

I'm thinking about leaving a fan on up there for now to move air about.

 

[Cubist]

The patterns of moisture droplets you are seeing will be where the edges of the roof tiles are in direct contact with the felt. These will be particularly cold spots and condensation will form rapidly there at times. Warm moist air from the rooms below is still getting into the loft and this is perfectly natural however - your inspection tours up there are adding to the problem. Every time you open the loft hatch, or leave it open, you are allowing blasts of warm air into the loft space.

Best advice is to stop checking as often as you are and keep the loft hatch shut.

 

[stuart45]

Adding eaves ventilation can be done in the soffits if you've got overhanging eaves. You'll always get condensation on the underside of the felt if it's surface temperature drops below the dew point.

 

[lizziecupcakes]

Thanks @Cubist , I've left my latch open now (it's in the bathroom) and the bathroom window is wide open.
I think I'll definitely reduce my future loft checks, but for now, Should I just close the latch now and let it dry by itself?
I'm a bit nervous that it's just not going to dry and I'll have a mould issue

 

[Aurelio]

I have exactly the same issues and have inspected the loft daily, I installed lap vents yesterday and patch repaired the ripped felt but it’s still dripping everywhere. I’m wondering whether to leave it a few days now and then contact a roofer if it doesn’t Improve.

 

[lizziecupcakes]

Adding eaves ventilation can be done in the soffits if you've got overhanging eaves. You'll always get condensation on the underside of the felt if it's surface temperature drops below the dew point.

so, I guess this will happen again during very extreme cold like we've had this past week, because the roof will be very cold, and the inside of my house will be very warm during these times. During December, I only out the heating on in the morning and evening, it was mild in the house otherwise.

 

[lizziecupcakes]

I have exactly the same issues and have inspected the loft daily, I installed lap vents yesterday and patch repaired the ripped felt but it’s still dripping everywhere. I’m wondering whether to leave it a few days now and then contact a roofer if it doesn’t Improve.

it's so annoying! I hope it dries up and never returns, and the rip is fixed. have you had this condensation problem before?

 

[lizziecupcakes]

Warm moist air from the rooms below is still getting into the loft and this is perfectly natural however - your inspection tours up there are adding to the problem. Every time you open the loft hatch, or leave it open, you are allowing blasts of warm air into the loft space.

does this mean there will always be some condensation, but the ventilation should dry it up ? or is the goal that no condensation should ever occur?

 

[Cubist]

Should I just close the latch now and let it dry by itself?

Yes.

I have exactly the same issues and have inspected the loft daily, I installed lap vents yesterday and patch repaired the ripped felt but it’s still dripping everywhere. I’m wondering whether to leave it a few days now and then contact a roofer if it doesn’t Improve.

You also are adding to the problem. Assuming that you have insulated the loft space properly this is critical insofar that this minimises the penetration of warm air from the rooms below - which is the source of moisture condensing out on the felt.

As with LCC - SHUT the loft hatch and reduce the frequency of your checks.

Some condensation in loft spaces is almost inevitable during cold snaps and some of this may fall onto other surfaces where the air currents through the loft space will cause it to evaporate. Reduce the frequency of your checks and do not open the loft hatch during cold snaps. You are building a mountain where there should be a molehill.

 

[DaveG]

If the loft hatch is in your bathroom it’s highly likely a lot of that moisture is shower/bath steam getting its way up there and condensing on the coldest places. What level of extraction do you have in your bathroom? If window is open I’m guessing extraction is currently minimal.
Decent extraction at source is crucial in order to get that moisture straight out so it can’t linger and leach into the loft space

 

[lizziecupcakes]

Thanks @Cubist - I just shut it now, but before I did, I noticed some of it has dried a bit now. I'll just leave it.
My concern is, if the latch is always closed, then when will I ever know the condensation is a problem e.g. mould and damaging the roof structure?

 

[stuart45]

does this mean there will always be some condensation, but the ventilation should dry it up ? or is the goal that no condensation should ever occur?

Ideally you avoid condensation, but the odds are that at some point the felt will be below the dew point. Adding insulation normally increases the chance of condensation forming, so more ventilation is usually added.
Insulation stops the heat escaping, but the moist air still goes into the roof space. Now it's colder it's relative humidity is higher and so it has more chance of condensing on the felt.

 

[lizziecupcakes]

If the loft hatch is in your bathroom it’s highly likely a lot of that moisture is shower/bath steam getting its way up there and condensing on the coldest places. What level of extraction do you have in your bathroom? If window is open I’m guessing extraction is currently minimal.
Decent extraction at source is crucial in order to get that moisture straight out so it can’t linger and leach into the loft space

we have mechanical ventilation - we always use it when we shower, and it generally always come on with the light on too. We also will start opening the window a crack after a shower, we just didn't do this this past week because it was too cold

 

[DaveG]

It can take as much as several hours to fully dehumidify a steamy bathroom and typically light switch triggered extractors are switching off after 15 minutes which just isn’t enough.
A fan with either a built in humidistat or an inline extractor wired to a separate humidistat is your best bet with the added bonus of never needing to open the window again. Appreciate there’s a cost involved in that but I think it would resolve your issue.
Also if in future there was an option to move the hatch out of the bathroom to another space, that would be worth doing too

 

[Cubist]

Thanks @Cubist - I just shut it now, but before I did, I noticed some of it has dried a bit now. I'll just leave it.
My concern is, if the latch is always closed, then when will I ever know the condensation is a problem e.g. mould and damaging the roof structure?

Periodic checks are always sensible but these need not be frequent and a little care in terms of timing is all that's needed. Given that you have recently installed loft insulation and additional vents its natural that you would want to keep an eye on things but once a year would typically be all that is needed normally.

 

[mardinor]

Check when you are fetching down the Christmas decorations!

 

[lizziecupcakes]

It can take as much as several hours to fully dehumidify a steamy bathroom and typically light switch triggered extractors are switching off after 15 minutes which just isn’t enough.
A fan with either a built in humidistat or an inline extractor wired to a separate humidistat is your best bet with the added bonus of never needing to open the window again. Appreciate there’s a cost involved in that but I think it would resolve your issue.
Also if in future there was an option to move the hatch out of the bathroom to another space, that would be worth doing too

I definitely plan to move this stupid hatch. Sorry, It just irks me that someone out it in the bathroom of all places!

When we do our future loft reno, the loft hatch will be boarded up, bathroom relocated and stairs to loft will be elsewhere.

I think i’ll just have to open the window with the extractor on for awhile. I can adjust it so that it turns off after an hour or so. I might do that