Positive Input Ventilation (PIV) is a whole-house ventilation system that's proven highly effective at reducing condensation and improving air quality. Here's everything you need to know.
How Does It Work?
A PIV unit is installed in the loft space (or in a central hall for flats). It continuously draws in fresh air from the loft — which is naturally drier and slightly filtered — and gently blows it into the living areas below through a single ceiling diffuser. This positive pressure causes stale, moist air to be displaced through existing gaps and vents in the building fabric.
Why Does It Reduce Condensation?
By continuously diluting the moist air inside the home with drier air from outside/the loft, the overall moisture level in the air drops. This means less moisture reaches cold surfaces and less condensation forms.
What Does It Fix?
PIV is highly effective against: - Condensation mould on walls and ceilings - Streaming windows - Musty smells - Poor air quality
It does not fix rising damp or penetrating damp, which have different causes.
Installation
A PIV unit can typically be installed in a few hours. It requires a power supply to the loft. Running costs are very low — typically under £20 per year in electricity.
Who Makes Them?
Nuaire and Envirovent are the two most common brands used by professionals.
Shadbolt Plastering supplies and installs PIV systems across South London and Surrey as part of our condensation control service.
Need Help with This?
Shadbolt Plastering provides professional plastering and damp proofing across South London and Surrey. Call us for a free assessment.
Call 07803 461497