A new boiler system was fitted when we moved into this house so the old gas heater in the lounge which also housed the back boiler was ripped out leaving a gaping hole. The twunt who did it just put some MDF over the hole in the wall, sealed and painted it.
Would I be right in thinking that this may be the reason there is now massive wet areas on the walls on both sides of the house above where the fireplace used to be.
DH pulled the MDF off the wall and it is very wet and there is water dripping down the exposed brickwork of the old fireplace.
DH thinks that because there is no ventilation in the hole, cold air coming down the chimney is meeting warm air in the house (have not put heating on yet 
)and creating condensation. A heck of a lot of it apparently! The walls are saturated and there is a horrible damp smell through the whole house.
This is a rented house BTW. Landlord was informed last week when I first noticed the damp patches which have now significantly spread. They have done bugger all.
We are going to have horrible mould in the winter are'nt we? Any thoughts??