This section explains the problems you can have with damp and excessive humidity, and how to remedy them.
Note also the comments in relation to building surveys and damp.
Note that condensation in the winter on single-glazed windows is normal and does not indicate excessive damp. Damp and humidity is not a 'problem' unless it is excessive and persists all year.
With older, brick-built houses, the walls are often porous; they can get damp. The rules for damp in the walls are:
For condensation the rules are:
Do not over-ventilate otherwise you will reduce the temperature
and the remaining moisture will condense; the art is in achieving