PIV vs Extractor Fans — What's the Difference?

When homeowners have a problem with condensation, damp or poor air quality, the two most common solutions they encounter are extractor fans and Positive Input Ventilation (PIV). Both improve ventilation — but they work in fundamentally different ways, and one is usually a far better fit than the other depending on your situation.

As engineers who install, service and repair both systems, here's our honest comparison.

How Extractor Fans Work

An extractor fan is a simple concept: it pulls stale, moist air out of a room and expels it outside through a duct in the wall or ceiling. You'll typically find them in bathrooms, kitchens and utility rooms — the areas where the most moisture is generated.

Extractor fans can be triggered in several ways:

• Manual switch — you turn it on and off yourself
• Linked to the light switch — it runs when the bathroom light is on, with an overrun timer
• Humidity sensor — it detects a rise in moisture and activates automatically
• Continuous running — some modern fans run at a low trickle rate permanently, boosting when humidity rises

They do a good job of removing moisture at source — while a shower is running, for instance — but their effect is limited to the room they're installed in.

How PIV Works

A PIV unit takes the opposite approach. Instead of extracting air from the home, it pushes fresh, filtered air in. The unit sits in the loft and draws air from the loft space, filters it, and delivers it into the property through a ceiling diffuser — usually on the upstairs landing.

This creates a slight positive pressure throughout the home, which gently displaces the stale, moisture-laden air outwards through natural leakage points: gaps around windows, doors, extractor vents and so on.

Head-to-Head Comparison

When an Extractor Fan Is the Right Choice

Extractor fans are ideal when the moisture problem is concentrated in one specific area and the rest of the house is fine. Common scenarios include:

• A bathroom with no window, where steam from showers has nowhere to go
• A kitchen that generates heavy cooking steam
• A utility room used for tumble-drying

If the condensation is localised and you can identify a clear source, an extractor fan is the simplest and cheapest fix. Building regulations require extractor fans in bathrooms and kitchens for new builds and renovations, so most homes already have them.

When PIV Is the Better Solution

PIV comes into its own when the problem is more widespread — which, in our experience, is more often than people realise. If you're seeing any of the following, a PIV unit is almost certainly the better answer:

• Condensation on bedroom windows — especially in the morning. Extractor fans can't help here because there's no extraction point in bedrooms.
• Mould in multiple rooms — a sign that the whole property has a ventilation deficit, not just one area.
• Musty, stale-smelling air — the home feels stuffy even when it looks clean. PIV constantly introduces fresh air.
• Condensation despite having extractor fans — if you already have fans in the bathroom and kitchen but still have damp issues elsewhere, the problem is whole-house ventilation.
• Older solid-wall properties — particularly common in northern England and Scotland, where cold walls provide extensive condensation surfaces.

Can You Use Both Together?

Absolutely — and in most cases we recommend it. Extractor fans and PIV complement each other well:

• The extractor fan handles high-moisture events at source — showers, cooking, boiling kettles
• The PIV unit maintains a healthy baseline ventilation rate for the whole house, preventing background moisture build-up

Think of it like this: the extractor fan deals with the spikes, and the PIV deals with the constant baseline. Together, they give you comprehensive moisture management without wasting energy or relying on open windows.

The Servicing Difference

Extractor fans are relatively simple devices. They benefit from occasional cleaning — removing dust from the grille and impeller — and replacement when they wear out (typically every five to ten years for a budget model).

PIV units are more sophisticated and benefit from annual professional servicing. This includes filter replacement, airflow measurement, motor inspection and a full system check. A well-maintained PIV unit will last ten to fifteen years or more, but a neglected one will gradually lose effectiveness as the filter blocks and airflow drops.