Mould problems with skylight

[Fee]

I have a square room in a bungalow with a sky-light as a window. The room has a flat ceiling - i.e. the ceiling isn't sloped like in an attic - and the sky light is built into the roof via a 'chute'. The walls of the 'chute' lead into the attic.

There is mould growing on the walls of the chute - due to water condensing, I guess, as it hits the cold air of the sky-light. I was wondering if it would help to prevent this by drilling a few holes in the side of the chute (into the attic space) and fixing a vent over it to let the air escape?

There is an existing vent in the room but it is very small. If fixing a vent within the chute is a solution, would it matter on which side this is done? e.g. facing the existing vent, facing away from the existing vent, etc.

Or if this is the wrong thing to do, can anyone offer any suggestions?
i.e. if I insulate the walls of the chute from the attic side will this solve the problem?

Many thanks!

 

[JohnD]

You need to insulate the walls of the shaft, at least as thoroughly as the loft floor/room ceiling.

the air inside the shaft is the same temperature as the room (or higher due to hot air rising) and will hold plenty of moisture, so if the shaft walls are cold then it is bound to give condensation.

If you are wrapping the shaft, you might find you can cut expanded polystyrene board to fit (at your builders merchant or DIY shed) with a breadknife, but it is difficult to joint the corners perfectly, so buy a roll of that loft insulation with a pink plastic sleeve, as it's cleaner to handle, and ties that round as well (or instead).

Try to avoid venting warm moist air into the cold attic as it will probably condense on something up there instead. If the room seems damp try to ventilate it to the outside, using a 100mm pipe if necessary (they are sold with extractor fans). Interestingly, if you have a ventilator in the ceiling of a room, esp. bathroom, with a pipe going up like a chimney, it doesn't need a fan as the rising damp air will take it out by convection.

 

[Fee]

I'm still experiencing problems with mould in the skylight and ceiling corners of my room. I went into the attic and wrapped the skylight chutes with sheepswool insulation and squeezed into the depper attic corners to insulate them but the mould still persists.

The room doesn't seem damp but it is used as a bedroom and I'm growing concerned about the effects.


There was mention of ventilating the air to the outside, using a pipe - how would this be done? I'm familiar with the type of extractor fans used in kitchens/bathrooms but these aren't really a solution for a bedroom on account of the whirring noise

How about a de-humidifier? Can anyone recommend one that isn't too big and doesn't make too much noise?

All advice is greatly appreciated! Thanks!