DIY Doctor UK DIY Forums

Ok so we have an attic bedroom that has a fixed staircase and no door or hatch, so open to the rest of the house. We have just had the whole roof replaced, yey no more leaks in bad weather! However we are now noticing patches of condensation on the walls, mainly appearing over night, query breathing? room is slept in!!! Patches seem to be where the air vents are for the roof I guess it's much colder there. Occasionally like today they have appeared during the day, whilst hubby was working from home up there.
We have purchased a 10ltr dehumidifier which we have on over night and leave the velux window open an inch or so on the catch.
What I want to know is if we need to keep the dehumidifier on 24/7 during colder months and is it pointless having the machine on if the window is also open? the room has a constant flow of air from the house. Any other tips to help with condensation spots would be helpful.

Hi Abby.wood
There is no point in running a de-humidifier with the windows open.
You need to get your roofing contractor back to identify issue with damp patches.
Regards S

Ok is this a roofing issue? There is no central heating on the 1st floor or in the attic except for the bathroom.
No patches appear when the dehumidifier is running or when the window is open.

Hi Abby.wood
When a re-roof is done where there is an attic room insulation should be added as part of the job. If insulation has been incorporated there should not be any cold spots where can condensation form.
From your description it is difficult to tell remotely what the issue is and using a surveyor may be your next move.
Regards S

Yes, no need to have the dehumidifier on when the window is open. What would be better is a fan with the window slightly open. I would then close the window at night and turn on the dehumidifier. Maybe have it on a timer save you doing it manually day and every night. It also sounds like there is very little insulation in the roof space. So maybe look at installing some blowing insulation. Ventilation is key, along with a warm roof. If you get that right, every else should fall into place for you. However, in the meantime, a fan will help the situation.
Regards,
Build4less

Thanks will look into that. Waiting in building regs coming to sign off the roof so can check the insulation with them.