Major condensation in loft space

[M005]

The solution to this seemed obvious but seemingly not

We live in a 5yr old detached house, have lived here for 3yrs. Every winter when the weather gets cold there is a problem with condensation in the loft, which drips onto everything up there causing mould etc.

It was well insulated, and I have last week added another 170mm to just over 1/2 the space - the 1/2 not covered by boxes etc. I have also found some areas that weren't insulated under some boarding put down by the previous owner, and have added 100mm of insulation board to the loft hatch as well.

None of this has made any difference

There is the standard ventilation around the edges, under the eves, which isn't blocked. Certainly the loft space feels cold.

So what am I missing?

Never had this before, even in houses with a lot less insulation, lofts are always dry, dusty places aren't they?

Thanks

[M005]

Thanks all, some great tips.

In response to the questions;

• The bathrooms do have vents, but to the outside, with the pipe being insulated as it passes through the loft space. We don't have the fans turned on.

• There are no downlighters upstairs.

• House is a large 4 bed, from memory when we bought it the upstairs was quoted ~ 795sqft.

• Persimmon BLOOR built the house.

• The ventilation by the eaves is covered with a plastic mesh.

• No CH items up there, just the cold water tank & header tank, all pipes are well insulated.

• Roof space is very large, apex is ~ 15ft high and distance between the triangular roof supports is ~ 10ft, with a futher ~10ft each side of that to the eaves. Total length of the space (length of apex) is ~ 40ft+ at a guess.

A few comments from above have got me thinking about airflow. Whilst the majority of the stuff is within the middle section (i.e. the middle 10ft) there is increasingly more stuff down one side in the outer 10ft to the eaves, which will be greatly affecting airflow.

I'm just about to head up there and have a good sort out / rearrange all the stuff and see of that makes a difference.

Thanks for all the inputs, I'll keep the thread updates with progress.

Edited by M005 on Thursday 17th December 09:09

[M005]

Wow - great discussion.

Sam 68 - seems I got my companies mixed up, Bloor built the house, persimmon did some of the others a few streets away. Ours is the only house of this design.

X 7usc - by header tank I mean very small additional cold water tank, definitely not hot water.

Jules S - you may be right with regard to the dew point, however what hasn't helped is the number of variables that have changed in a short space of time; extra insulation added, weather got colder, stuff in loft moved well away from the eves to allow better ventilation.

I went up this morning (07h00) to get the NHBC stuff, and my feeling was that it felt a lot colder up there (better insulation & increased ventilation) but that there was also more water dripping everywhere.

Will give Bloor and NHBC a call today and see where I get to.

[M005]

Dave_ST220 said:

Martin Keene said:

I found this hard to believe as it had been fine for 12 years. When I sat down and though it through, I realised it started after swmbo moved in and a lot of stuff got put in the loft. Being terreced the vents where on the front and rear eves and we had the contents of the loft on a boarded section across the middle.

A damn good clear out, and rearranging what was left against the party Walls in the loft removed the condensation. We had blocked the airflow in the loft with all the st in there.

Exact same deal here, loft got so full the airflow...err...didn't!! Good clear out & all sorted.

Interesting distinction I hadn't picked up on.

All our stuff is now in the centre boarded section, whereas some had been along the edges close to the eves.

The eves are front & rear of our property as well, and I assumed that the airflow would go over the top of anything stacked in the middle?

[M005]

Seems I'm on my own with this; Bloor aren't interested as it is 5yrs old, and NHBC aren't interested as it isn't structural.

Had a long chat with the NHBC assessor and they are sending me out a leaflet about reducing condensation in the roof space; apparently they get a lot of calls about it at this time of year.

From the discussions the main themes seem to be ventilation (increasing it - also mentioned that anything in the roof space will restrict ventilation) and restricing the moisture from the house getting up there, rather than the heat. She wouldn't be drawn on whether extra insulation, or proper insulation, was a good or bad thing.
Aparently trickle vents should be open even during the winter, washing shouldn't be dried on radiators, or on airers near radiators, etc.

One point she did stress was that the roof space isn't designed as a storage space, therefore the short answer to the issue is don't store anything up there!!

[M005]

Definitely condensation.

This is our 3rd winter there and it has always been as issue, getting worse each winter - I guess as more stuff is put up there.