Modern well insulated buildings can have a adverse effect on relative humidity levels in the home and this can have a detrimental effect on your health. If the the humidity level is too low then the atmosphere is dry and can be bad for allergy suffers, it can also effect the building and cause cracking. If the humidity levels are too high then the atmosphere is damp and this can help profligate bacteria and mould equally effecting your health.
The ideal relative Humidity level in your home in the UK ideally wants to be around 50%, this can vary between individuals some may like it high whilst others lower so between 40 and 60% is good. Relative humidity depends on the atmospheric conditions and the air temperatures of the day and can vary accordingly but mechanical ventilation can help in obtaining and keep a fairly consistent humidity level.
A excellent solution to controlling relative humidity in your home is the use a enthalpy energy recovery unit, replacing your conventional heat recovery ventilation exchanger (HRV) with a enthalpy unit turns your mechanical ventilation system into a energy recovery system (ERV). This will recover up to 70% of the humidity. Then in winter this combats the dry air and in the summer months reduces the high humidity. Using a special membrane it reintroduces the filtered moisture and prevents any ingress of pollution.