Mould and damp in attic space

We noticed a similar issue in our attic a few years ago when the weather was cold. House all recently renovated and insulated, ended up getting roof vents installed and the problem was solved. Our neighbours also noticed a similar issue after getting their place insulated.

Check that the rockwool is not blocking the vents in the soffit. If it is, pull it back a little at the vents.

Soffit vents may be covered with your rock wool. Make 100 percent sure they are free and open.

Other than that. They may not be good enough to allow good airflow. You might need extra vent tile at the top to promote airflow soffit to vent pulling out the warm moist air.

Finally mhrv. The roof venting of these is probably the worst method tbh it's the reason I avoided this type of exhaust ventilation in mine. I opted to go through gable wall. The warm exhaust air from your mhrv can cling to to the inside of your flue stack and fall back down.

I would definitely have the exhaust of the mhrv checked both at the tile and down the exhaust pipe to unit.

Plumbing vents?

Would need to understand the detailing here, it's unclear whether your new ewi or your rock wool, or both. Is impacting airflow. Was any of this a problem prior to the works?

It's definitely not to be expected. Sole vents are useless unless there's supply . A 'flow' of air is required. Vent to vent. Soffit to vent is best. Or soffit to ridge even more superior.

They should be checking the ventilation is working. Without adequate airflow then moisture cannot disappate.

You may need more vents you may need soffits checked.

i took photos tonight - it doesn’t tell

the full picture there’s a lot of condensation

If you're seeing a gap between the exhaust pipe and the soffit, then yes, that's a probable cause! Brilliant!

I didn't want to to be too negative about what the installer told you yesterday (the copper CAT5 wire), but seeing condensation on the CAT isn't a cause of the high humidity, but is an indicator or symptom of the issue.

Go chase the installer to correct that leak now. 👍️

Pure sub par workmanship. Really lazy stuff that especially an extraction zone rather than supply.

One of the core reasons I went self install. I know every mm of the work.

Good news. The next week where we have low temps and little wind will be a good test.

I think you've still got a lot of trapped moisture up there from the previous issues - in the glasswool, the joists, rafters and the flooring. It could be a factor and I know that if I was look at any given roof during a period of very cold and wind-less weather, you'll eventually find condensation.

Plus, I can't work out... why is that glasswool piled against the roof? Is it blocking the vents?

I was wondering what that pipe was. In that case if it's "supplementary ventilation" from the soffit then I'd feel like I'm right with what I said above. It's going to take some weeks to shift that humidity-load out of the attic. Would you agree?

I don't think the drain is the problem water will flow out of that and straight out the house at irregular intervals. It's gone in seconds. I wouldn't even bother my arse insulating it.

See my comments above on extract.

It should be clearing it in under 5 minutes. And even then you should have barely any surface condensation on mirror or windows.

2 things.

Your door gaps are non existent or too small.

You aren't using boost button or have none in the wetrooms.

If the door gaps are not there the required fresh supply from non extract rooms isn't there so your system isn't working as intended.

It's meant to clear the room quickly. There should be a minimum for Bathrooms I think is 6l/s. But should really be like 8l/s of air change.

What was the measured air change on the bathroom exhaust when it was commissioned you should have been given a reading sheet.