Loft felt wet on one side only?

[F54Mini]

Hi

I have part converted our loft to use as an office so 50mm rockwall between rafters and 50mm Celotex over them.

The eaves have sliding doors so no insulation in those.

At the moment one side of the roof is wet, presumably its condensation causing it. The felt is dripping slightly on that side and the rockwall is a little wet. Even the bit in the eaves thats not insulated is wet, dripping onto the stuff we have stored in the eaves.

Is that normal because of the weather being so cold? Would sticking a heater in there for an hour a day help or make it worse?

I have installed some lap vents in the felt to allow airflow and the soffits are not blocked, I made sure there was airflor up through the rafters, across the ridge and down the other side.

Thanks

 

[motorbiking]

It sounds like condensation. You want to avoid heating an uninsulated loft area. Do you have a bathroom vent or downlighter etc. allowing warm moist air to escape in to the loft?

 

[F54Mini]

It sounds like condensation. You want to avoid heating an uninsulated loft area. Do you have a bathroom vent or downlighter etc. allowing warm moist air to escape in to the loft?

Weirdly the bathroom is on the side of the house where the loft felt is dry as a bone.

It’s the front of the house that has the wet felt. I don’t understand why it’s wet on one side only, both sides have identical insulation down to the eaves.

I have been using a heater up there recently to perhaps because the eaves just have sliding doors and are not insulated, the heater is causing the condensation?

Long term plan is to replace the sliding doors on the eaves with a stud insulated wall but haven’t got round to it yet.

 

[motorbiking]

A photo would help, but my guess is some of the warm air is escaping in to the cold loft. It could even be the difference between North and South facing.

 

[F54Mini]

A photo would help, but my guess is some of the warm air is escaping in to the cold loft. It could even be the difference between North and South facing.

Will try to get a photo, the side with condensation is North facing and the side which is dry is south facing. I don’t recall condensation in the summer months as the insulation was added in July. It only started getting wet on that side in the past few weeks.

 

[JohnD]

Will try to get a photo, the side with condensation is North facing and the side which is dry is south facing. I don’t recall condensation in the summer months as the insulation was added in July. It only started getting wet on that side in the past few weeks.

That's typical. If there is sunlight, the south facing slope will be warmer and frost will melt off it.

 

[JohnD]

See also https://www.diynot.com/diy/threads/condensation-in-loft-answers.160032/

 

[Why Not Indeed]

I don’t recall condensation in the summer months

Makes sense, much smaller difference in temperature in summer between inside and outside the loft.