vlažnost

1. (of air) humidity
   Danas je vlažnost vazduha preko osamdeset posto. — Today the humidity is over eighty percent.
2. (of skin, walls, soil) moisture; dampness
   Ova krema čuva vlažnost kože ceo dan. — This cream keeps your skin moist all day.
   Zbog vlažnosti zidova u stanu ima buđi. — Because of the damp walls, there's mould in the flat.

For damp in a house, «vlaga» is the more everyday word.