Positive Input Ventilation (PIV) units seem to be a new thing for landlords to battle this problem. I think it basically trickles in cold (and therefore drier)

Positive Input Ventilation (PIV) units seem to be a new thing for landlords to battle this problem. I think it basically trickles in cold (and therefore drier) air into a central space to reduce humidity, like an (slower, quieter) extractor fan in reverse. Seems a bit of a conflict of interest still, especially if the tenant is paying for heating.