New built cellar with condensation

[borisbear]

I have a damp problem in a cellar.
This problem is not the normal one i think. The walls and floor are free of all damp but i have the formation of condensation on the ceiling.
The ceiling of the cellar is constructed from a tee beam floor which forms the exterior patio above.
The ceiling i have insulated with 40mm rigid styrofoam type insulation against the underside of the tee beams and is then boarded over with mdf to finish.
The condensation seems to be forming in the gaps between the concrete blobks and the insulation boards. This dampness seems to soak through the mdf and then forms mouldy patch on the ceiling.
The cellar room itself stays at a fairly constant temperature, but the patio/ceiling temperature changes with the sun shine on it. The cellar room currently has one access door and no windows or ventilation.
Can any one help?

 

[JohnD]

Couple of points I can see:

If it is newly built, the I expect the ?concrete walls and floor of the cellar will still be drying out (presume you have DPCs?) and releasing moisture into the air. as you say it is unventilated this moisture will be looking for a cold surface to condense on. You cellar temp may be about 15 degress C (typical for underground rooms) and at this time of year the concrete patio will be very cold. You need ventilation. If you can bring in cold air from outside rather than warm air from the house, it will be have less water vapour in it.

You really need a moisture vapour barrier on the warm side of the "roof" (that is, the room side of the insulation) to keep the moist air from reaching the cold surface. this could be placed above the cladding boards, but the space ought to be ventilated to the outside (in a way that won't allow rain in).

If you want to dry out the moisture from the walls, you couldhire a dehumidifier, but this is an expensive and short-term fix.

Nice idea, though. Is it a wine cellar or your nuclear bunker?

 

[borisbear]

Many thanks for your comments.
I've had a dehumidifier in the cellar for about a month now, i doesn't really gather any moisture as the room itself is dry as a bone.
Its just this problem in the ceiling thats a real pain.
Its been built as a wine cellar/games room and the plan was working so well until we put the insualtion in the ceiling.
I have removed the mould from the ceiling several times now with my wife vacuum cleaner (which she is not over the moon about), but each time the mould returns although i think it is getting less.
So may be it time what moisture there was in the ceiling gap will have worked its way through and perhaps in will dry up?
Any further comments are welcome!

 

[Nige F]

You need to kill the mould with a weak bleach solution.and buy a new hoover. it`s full of spores now