Using this dew point calculator indicates that if any of the walls in the hallway dip below / around 13C then you will get condensation on those surfaces based on the values shown by the cursor on this sample of data. The values indicate a relatively high likelihood of condensation later on in the year. I guess there are a few ways of tackling this: dehumidifier, a more active ventilation strategy, some heating to raise the minimum temperature in the hallway etc.
