Positive Input Ventilation (PIV) Installation in London
Persistent condensation, black mould that keeps coming back, or stale air you can’t shift — a PIV system treats the root cause permanently. We survey first, then recommend the right solution for your property.
Positive Input Ventilation — How It Works
Positive input ventilation (PIV) — also called positive pressure ventilation (PPV) — is a whole-home ventilation system that continuously supplies filtered fresh air into your property at low positive pressure.
This gently pressurised fresh air displaces damp, moisture-laden indoor air through natural gaps in the building fabric — around windows, doors and trickle vents — without mechanical extraction. Indoor humidity stabilises, condensation stops forming, and mould loses the conditions it needs to survive.
Not certain condensation is your problem? Book a damp survey — we’ll confirm the cause before recommending any treatment.
How PIV Works — Step by Step
Signs a PIV System Is the Right Solution for Your Property
If you recognise any of the following, excess indoor humidity is almost certainly the cause — and a PIV system is likely the most effective permanent fix.
Water on windows every morning
Droplets running down the inside of glass in bedrooms or living rooms — the clearest sign of excess indoor humidity, not a structural fault
Black mould that keeps returning
If you clean mould and it reappears within weeks, the underlying humidity hasn’t been addressed — PIV removes the moisture mould needs to grow
Musty or stale-smelling rooms
A persistent damp odour — particularly in bedrooms or infrequently used rooms — is caused by mould spores and stale humid air that hasn’t been replaced
Mould behind furniture or in wardrobes
Mould on cold external walls behind sofas or inside wardrobes is a cold-bridging and ventilation issue — PIV directly addresses the humidity that feeds it
Mould in a flat with no obvious damp
In London flats on upper floors or in modern well-insulated buildings, condensation is almost always the cause of mould — PIV is highly effective in these properties
Rooms that feel airless or stuffy
Tightly draught-proofed and well-insulated homes can suffer from poor air exchange — PIV solves this without sacrificing warmth or requiring window-opening
PIV for Houses and Flats Across London
The type of PIV unit we install depends on your property. Both systems work on the same principle — the installation method differs.
Loft-Mounted PIV Unit
Loft-mounted PIV — installed £870 – £1,020
The standard solution for houses with a loft space. The unit sits discreetly in the loft, draws fresh air from the loft environment, filters it, and distributes it down into the hallway or landing through a ceiling diffuser.
- Victorian and Edwardian terraces with solid brick walls
- Semi-detached and detached houses
- Properties with extensions or added rooms
- Homes with draught-proofing installed
Most units include an optional heating element to warm incoming air in winter — a practical consideration for London’s colder months.
Wall-Mounted PIV Unit
Wall-mounted PIV — installed £950 – £1,070
For flats without loft access. Fixed to an internal wall — typically in a hallway or landing — and ducted through to an external wall. Operates identically to a loft unit: filtered fresh air at positive pressure.
- Ground floor and basement flats
- Top floor flats in converted houses
- Modern purpose-built apartments
- HMOs and rented properties
Landlords: PIV installation supports compliance with the Homes (Fitness for Human Habitation) Act 2018. We provide documentation on request.
PIV Installation — Our Process
We survey before we recommend. Every job begins with a proper assessment of your property and the cause of the problem.
Survey
CSRT-qualified specialist assesses moisture levels, airflow and structural factors specific to your property
Fixed Quote
Written, itemised quote with no hidden charges — and honest advice on whether PIV is the right solution
Installation
Half-day for loft units, 2–4 hours for flat wall-mount. All electrical work to Part P standards. Site left clean
Commissioning
Unit set to the correct flow rate for your property size, confirmed operational, and handed over with aftercare guidance
PIV Systems We Install Across London
Loft and wall-mounted PIV units installed in London houses and flats. Real installations — no stock photography.
Positive Input Ventilation — house installation
Moisture removal at source
Positive pressure ventilation duct — flat installation
PIV Installation Cost in London
Fixed, itemised quotes provided after survey. No hidden charges. Costs depend on property type, unit specification, and whether additional ductwork is required.
| Installation Type | Includes | Typical Cost |
|---|---|---|
| Loft-Mounted PIV Unit — Heated (House) | Unit, ceiling diffuser, all labour, Part P electrical sign-off | £870 – £1,020 |
| Wall-Mounted PIV Unit (Flat) | Unit, external wall ducting, all labour, Part P electrical sign-off | £950 – £1,070 |
| Running Costs (Annual Electricity) | Continuous low-wattage operation — quieter and cheaper than a dehumidifier | ~£50 – £70 / year |
PIV vs Dehumidifier — Which Is Better for Condensation?
This is the most common question we’re asked, and the answer matters because the wrong choice wastes money without fixing the problem.
| ✓ PIV System | Dehumidifier | |
|---|---|---|
| How it works | Replaces indoor air continuously with filtered outdoor air | Recirculates and dries existing indoor air — no fresh air introduced |
| Condensation control | Permanent — prevents condensation forming on cold surfaces overnight | Reduces peak humidity but doesn’t prevent overnight condensation reliably |
| Air quality | Improves — filtered fresh air continuously replaces stale indoor air | No improvement — same air recirculated, allergens remain |
| Running cost | ~£50–£70/year electricity — low-wattage continuous operation | £150–£300/year electricity — higher wattage unit required for effect |
| Maintenance | Annual filter check — no daily emptying | Water reservoir requires daily emptying when in heavy use |
| Noise | Near-silent continuous operation | Audible compressor cycle — not suitable in bedrooms overnight |
| Installation | Permanent, out-of-sight — no space taken up in rooms | Freestanding unit that must be repositioned and plugged in |
| Suitable for | Condensation-related damp and mould — most London homes and flats | Temporary high-humidity events (building drying out, flood recovery) |
Note: PIV is the right solution for condensation-related damp. If your property has rising damp or penetrating damp, the structural cause must be treated first — PIV is not a substitute for damp proofing. Not sure which type of damp you have? Read our guide →
PIV Installation Across London & Hertfordshire
We install positive input ventilation systems across some boroughs, with particular depth of experience in the residential areas of North, North West and West London.
Not sure if we cover your area? Call 020 4542 6114 — we cover most of Greater London and Hertfordshire.
PIV Installation — Frequently Asked Questions
What is positive input ventilation and how does it work?
How much does PIV installation cost in London?
Is PIV suitable for flats?
How quickly will I see results after PIV installation?
How long does PIV installation take?
Is PIV better than a dehumidifier for condensation?
Trusted by Homeowners & Landlords Across London
Book Your Free PIV Survey
Speak to a CSRT-Qualified Specialist
Tell us about your property and the problem you’re experiencing. We’ll confirm whether PIV is the right solution and talk you through exactly what to expect before you commit to anything.
Request a PIV Survey
Fill in your details and we’ll get back to you promptly. Same-week appointments available.
Stop Condensation at the Source
PIV treats the cause of condensation permanently — not just the symptoms. Get a proper diagnosis from a CSRT-qualified specialist before spending money on anything else.