An interesting thing that I was made aware of recently, is that the natural gas piped into our homes produces a surprising amount of water vapour when it combusts.
With modern boilers, this is not a problem since they are well sealed and vented via flues to the outside. However, where there are gas fires, gas hobs or gas ovens, these might contribute to the total amount of moisture in the house, thus raising the humidity & potential for condensation.
The evidence-led approach provides a clear understanding of why, how, what and where the house is reacting in this way. Looking at things in context, the short, medium and long term also, makes you think about future ownership of this house and how I could make a more positive contribution as part of its history.