It's both. Humidity will more readily condense on lower temperature walls and windows resulting in mould. You need a combination of ventilation to lower the dew

It's both. Humidity will more readily condense on lower temperature walls and windows resulting in mould. You need a combination of ventilation to lower the dewpoint and warmer walls so as they don't meet the dewpoint. Your choice of spelling of "mold" is consistent with your apparent lack of experience living in high humidity parts of the world :-)