concrete ceiling and condensation

[max3d]

hi all and thanks in advance. We have an outhouse with a concrete ceiling and a single brick wall (joining onto the main house) i have sealed the walls and put some phenolic insulation board 30mm foil lined onto batons to try to keep some of the heat into the room. i have also batoned the ceiling and added the same boards to it. the problem i have no is the condensation is still on the ceiling and is dropping onto the boards and coming though the ceiling hole for the light fitting. i am trying to keep the room well ventalated by open window etc also using a dehumidifier which gets full daily. now im thinking about what to do to solve it and one idea i have come up with is to buy a roll of loft insulation remove one of the boards from the ceiling and slide the loft insulation in between the phenolic boards then replacing the removed board ( with some loft insulation onto it) now my thoughts are this will butt up against the concrete ceiling and prevent the warm air hitting the cold surface and forming the persky water. does this sound like a winner or is there a better way of doing this.
thanks
dave

 

[foxhole]

Are you sure you don't have a leaking roof?

 

[max3d]

200% sure it also happens in the other part of the building where the ceiling continues which isnt insulated you can see the build up of condensation on the ceiling opening the back door and using the dehumidifier stops that albeit a cold solution but its just now this part is insulated i need the water to not build up and come through hence the idea with the loft insulation.