Condensation happens when moist air comes into contact with air or a surface which is at a lower temperature.
Water produced from condensation is generally noticeable where it forms on non-absorbent surface (i.e. windows or tiles) but it can form on any surface and it may not be noticed until mould growth or rotting of material occurs.
How to help with this problem is to remove the moisture to the outside by ventilation ie. Installing a suitable extractor fan in the kitchen and bathroom and if you are replacing windows ensure they have trickle vents.
If you are providing a tumble dryer to the property ensure that you put the outlet pipe through an outside wall.
Insulate the loft ensuring that the openings under the eaves are not blocked.
Draught proof windows and doors avoiding rooms where a gas burning appliance or solid fuel in installed as these appliances need a constant source of fresh air to ensure proper and safe combustion.