If condensation and mould keep coming back despite opening windows and using extractor fans, whole-house ventilation may be the answer. Positive input ventilation, or PIV, is one of the most common options.
How PIV works
A PIV unit is usually fitted in the loft, or in a cupboard in flats without loft access. It draws in fresh, filtered air and gently pushes it into the home, usually through a ceiling diffuser on the landing. This slightly raises the air pressure inside, so moist, stale air is pushed out through natural gaps in the building. The result is a steady change of air that dilutes moisture before it can condense.
Which homes it suits
- Homes with condensation and mould in several rooms
- Properties that have been draught-proofed or had new windows fitted, reducing natural air movement
- Flats and houses where opening windows isn’t always practical
- Rented properties where a low-maintenance, always-on solution is helpful
When it isn’t the answer
PIV helps with condensation. It will not fix rising damp, penetrating damp or a leak. If the damp has another cause, that needs dealing with first, which is why a survey matters.
Working alongside other measures
PIV works best alongside good extraction in kitchens and bathrooms. In some homes, continuous-running extractor fans or individual room heat recovery units may be a better fit. The right solution depends on the layout of the property and how it is used.
Running costs and maintenance
PIV units are designed to run continuously at low speed. Filters need replacing periodically, following the manufacturer’s guidance.
Our surveyors measure humidity and surface temperatures to understand why condensation is forming, then recommend the most suitable ventilation. Learn more about our condensation and mould control service.
