Best PIV Units for Landlords 2026: Stop Condensation Mould at Source

Under Awaab's Law, landlords must not only remediate damp and mould when it is reported — they must address the root cause. For the majority of UK social housing, that root cause is condensation: moisture-laden air settling on cold surfaces because the property is not adequately ventilated. Positive Input Ventilation (PIV) is one of the most effective and cost-efficient solutions available.

What is a PIV unit?

A Positive Input Ventilation unit is a mechanical ventilation system that introduces a continuous supply of filtered, fresh air into a property. Installed in the loft space (for houses) or a cupboard or hallway (for flats without lofts), the unit draws air from outside, passes it through a filter, and gently forces it into the living spaces below via a ceiling diffuser — typically positioned in the landing or hallway.

This continuous positive pressure pushes the warm, humid air that builds up during daily activities — cooking, bathing, breathing, drying laundry — out through natural gaps in the building fabric, eliminating the conditions that cause condensation mould to form.

Unlike extract fans, which remove air only when operating, PIV units work continuously at low speed — 24 hours a day, 7 days a week. This means they tackle the underlying ventilation deficit rather than responding reactively to individual moisture events.

Why PIV units matter under Awaab's Law

The Housing Ombudsman has been clear in its casework: surface mould treatment — painting over affected areas, cleaning with anti-mould products — is not a satisfactory long-term remedy for properties with chronic condensation problems. Where the root cause is inadequate ventilation, any remediation that does not address the ventilation itself is likely to result in recurrence.

Under Awaab's Law, recurrence is itself a failure. If a landlord remediates a mould issue in October and the same property reports the same issue the following spring, the landlord has not complied — they have managed a symptom rather than eliminated a hazard.

A PIV unit, properly installed and maintained, eliminates the conditions that cause condensation mould in the first place. It is a permanent solution rather than a periodic treatment. For landlords with stock where condensation mould is a recurring problem, PIV installation is increasingly the appropriate long-term response.

Types of PIV unit

Loft-mounted PIV units are the most common type for houses with a loft space. The unit sits in the loft and draws air from the loft void. Many models include a small heater element that tempers the air before it enters the property, preventing cold draughts in winter. The Nuaire Drimaster range is the UK market leader.

Wall-mounted or through-wall PIV units are designed for flats and properties without a loft. They draw air directly from outside through a duct, filter it, and distribute it into the living space. They are slightly more visible than loft units but effective in properties where loft installation is not possible.

PIV units with humidity sensing include an integrated or wireless humidity sensor that automatically boosts airflow when indoor humidity rises above a set threshold — for example, during and after a shower, or when a washing machine is running. This maximises efficiency and is particularly useful in properties with high-humidity rooms.

Recommended PIV units for landlords

The UK market for PIV units is dominated by a small number of specialist manufacturers. For landlord applications, the following are the most widely used and recommended:

Nuaire DRI-ECO-HC (Hall Control)is the UK's best-selling loft PIV unit. The Hall Control designation means all settings can be adjusted from the ceiling diffuser without entering the loft — important for maintenance access. Compatible with optional humidity sensors and CO2 detectors. Five-year warranty. It is the default choice for most housing associations and local authority landlords.

Nuaire Drimaster Eco Heat adds an integral 400W heater behind the ceiling diffuser, tempering incoming air before it enters the property. This prevents cold draughts and is particularly appropriate for older, poorly insulated properties and those in colder northern climates.

Nuaire Drimaster Eco Link is sensor-compatible — it can be connected to an optional wireless humidity sensor, allowing the unit to automatically boost ventilation when humidity rises. Useful for properties where tenant behaviour is a factor (for example, where tenants habitually dry laundry indoors or cook without using extractor fans).

What PIV units cost

Loft-mounted PIV units typically cost between £170 and £450 for the unit itself, depending on the model and features. Installation by a qualified electrician typically adds £150–£300. The total installed cost of a loft PIV is therefore generally in the range of £350–£750.

Running costs are very low — a standard loft PIV consumes approximately 10–25 watts continuously, equivalent to roughly £15–40 per year at current electricity prices. Filters require cleaning or replacement every 3–5 years at minimal cost.

When set against the cost of repeated mould remediation treatments, the reputational and legal exposure from recurring cases under Awaab's Law, and the potential compensation liability, the investment case for PIV installation in condensation-prone properties is strong.

Are PIV units a landlord's responsibility?

The installation of a PIV unit is a landlord-initiated improvement rather than a repair — and therein lies an important distinction. If a tenant reports condensation mould and the landlord investigates and identifies inadequate ventilation as the root cause, the landlord is responsible for addressing that root cause. In a growing body of Ombudsman casework, failure to install adequate ventilation in properties with chronic condensation has been treated as a systemic failure.

Maintenance of an installed PIV unit — filter replacement, functionality checks — is generally the landlord's responsibility. Tenants should be provided with written guidance on how the unit works and not instructed to cover or disable it.