Take a look at your heating!
Causes of Damp
Damp can be caused by a number of problems. These include rising damp, rain leakage, faulty plumbing etc. These causes can be remedied by physical means ie house repair, barriers etc. Another major cause of damp is condensation. Condensation occurs when surfaces are cold and when the moisture content of the air is high. When moist air comes into contact with a colder surface like a wall, window, mirror etc. the air can't hold the moisture and tiny drops of water appear. Preventing condensation is challenging.
Methods to Reduce Condensation
Typical solutions to condensation focus on reducing the moisture in the air by either ventilation or dehumidification. Since these methods cool the air, they place an additional load on your heating systems. The air, once reheated, will then pick up moisture and will have to be cooled and reheated once again.
This begs the question "Is there a way to reduce condensation that doesn't work against your heating system?
A Better Solution To Eliminate Condensation
Condensation occurs when surfaces are cold and when the moisture content of the air is high. Rather than trying to reduce moisture in the air, can surfaces be kept warm?
Infrared heating heats objects / people rather than the air. As a result, ceilings and walls are 2 to 3 degrees warmer than the air. Unlike convection heating, infrared heating doesn't circulate warm moist air. Without the moist air and without any cold surfaces for condensation to occur on, damp from condensation isn't just reduced, it is eliminated.
If you have damp problems caused by condensation, then either replace or augmenting your convection heating system with far infrared heating panels. Not only will stop the damp and create a warm healthy environment, but your energy usage will also be cut by half together with zero maintenance costs.