A positive input ventilation (PIV) unit is typically fitted in the loft (or sometimes in a hallway cupboard in flats without loft access) and continuously introduces filtered fresh air into the home at a low level, gently pushing stale, humid air out through natural gaps, trickle vents, and extractor fans rather than relying on those alone to clear moisture.<\/p>\n
An extractor fan removes moist air from a specific room, on demand or on a timer. A PIV system works continuously and whole-house, diluting humidity throughout the property rather than targeting one room at a time. The two aren’t mutually exclusive — a PIV unit doesn’t replace bathroom or kitchen extraction, it supplements it for the wider condensation problem that affects hallways, bedrooms, and other rooms without their own extraction.<\/p>\n
A PIV unit is a bigger investment than an extractor fan but meaningfully less than damp-proofing treatments like DPC injection or tanking — get quotes from more than one installer, and check whether the property’s loft has enough clear space and suitable access for the unit and its ducting before assuming it’s a straightforward fit.<\/p>\n