Quick answer: A positive input ventilation (PIV) unit costs £400–£800 installed and is the most cost-effective whole-home fix for most houses. Whole-house MVHR costs £3,000–£8,000 and suits new build or major refurbishment. An independent condensation or damp survey costs £200–£400 and is worth it wherever the cause is unclear. The smaller measures — extract fans, trickle vents — are priced per property.
Condensation is cheap to make worse and moderately priced to fix properly. The mistake that costs the most is spending on the wrong solution because the cause was never diagnosed. This guide gives the figures that are established, explains what moves them, and sets out when the survey pays for itself.
The main items
Positive input ventilation (PIV) unit, installed — £400–£800
What moves the price: loft access and layout, whether an existing loft hatch run and power supply can be reused, the PIV variant (some models include a heater to temper the incoming air), and any electrical work required. In a straightforward loft with a nearby fused spur, expect the lower end; a difficult loft or a new circuit pushes it up.
MVHR (mechanical ventilation with heat recovery), whole house, installed — £3,000–£8,000
What moves the price: property size, the number of wet rooms and habitable rooms to serve, how difficult the ductwork routing is, and — the biggest single factor — whether it is fitted during a refurbishment or retrofitted into a finished home. Fitting it while floors are up and walls are open can halve the labour.
Independent condensation or damp survey — £200–£400
What moves the price: property size and location. What makes it worth paying for is a written report from a PCA-accredited or RICS-qualified surveyor — not a free visit from a contractor who sells the treatment.
Priced per property — get a quote
These vary too much with the property to give a meaningful single range. They depend on room count, access, the existing system and the building fabric:
- Continuous mechanical extract (dMEV) fans — per fan or per property
- Intermittent extract fan, supplied and fitted
- Trickle vents retrofitted to existing windows
- Loft, cavity or solid-wall insulation
- Heating system upgrades and controls
- Dehumidifier — unit cost plus running cost
Get written quotes for these from a verified specialist. The cost of a badly-specified job is not the quote — it is the second job when the first one does not work.
DIY versus a professional install
Some of the cheapest wins are genuinely DIY: opening trickle vents that were left shut, clearing a blocked airbrick, moving furniture a few centimetres off an external wall, and replacing a dead pull-cord bathroom fan with a like-for-like unit. None of that needs a contractor.
Where a professional is worth the money: anything involving the loft (PIV), anything that has to be ducted correctly to outside, any electrical work beyond a like-for-like fan swap, MVHR of any kind, and insulation. A PIV unit bought online and fitted by an untrained person is a common source of *new* problems — condensation in the loft, noise, a unit drawing from an unventilated void. The install is most of the value.
A worked example
A landlord with a 1930s three-bed semi gets a condensation report: mould in both back bedrooms, streaming kitchen windows, sealed replacement windows fitted three years ago with no trickle vents.
- Independent damp survey to confirm condensation and rule out anything structural: £300
- Trickle vents retrofitted to the four main rooms (new sashes): quote — assume mid-range
- Kitchen and bathroom intermittent fans replaced with continuous (dMEV), properly ducted: quote
- PIV unit in the loft, using the existing hatch and a nearby spur: £600
The survey plus PIV is £900 of firm cost; the vents and fans are quoted per the property. The whole package typically lands between £1,200 and £2,000 and resolves the house. Set against a returning mould problem and a possible disrepair claim, it is the cheap option.
When the survey pays for itself
A £200–£400 survey is cheap insurance against a four-figure mistake. Pay for one when:
- The cause is genuinely unclear.
- A previous "fix" did not work.
- A contractor has diagnosed rising damp and wants to inject a chemical damp-proof course.
- You are a landlord who needs written evidence of investigation for Awaab's Law or a disrepair claim.
Skip it only when the cause is obvious and the fix is low-cost and low-risk — for example, replacing a dead bathroom fan.
What drives the total on a real job
Three things move a condensation quote more than anything else:
Access. A PIV unit in an easy loft with power nearby is a two-hour job. The same unit where the loft is boarded and full of storage, or has no light or power, is half a day plus an electrician. Ductwork routing is the equivalent variable for MVHR.
How many rooms are affected. A single mouldy bathroom is a one-fan fix. Mould in three bedrooms and a kitchen is a whole-house strategy — background ventilation everywhere, extract at every wet room, and usually a supply system on top.
The building fabric. If the underlying problem is a cold, uninsulated wall, no amount of ventilation fully fixes it, and the real cost is the insulation. Solid-wall insulation runs into thousands and needs designing so it does not trap moisture in the wall.
What to expect on the invoice
A competent condensation fix is usually a package, not a single line: often a PIV unit plus one or two upgraded extract fans plus trickle vents, sometimes with insulation to a specific cold wall. A single-line quote for one product against a whole-home problem is a warning sign — ask what the diagnosis was.
Running costs
The fixes are cheap to run. A PIV unit uses a few pounds of electricity a year; a continuous extract fan is designed to run at a few watts. A dehumidifier is the exception — it uses electricity continuously and, over a winter, its running cost can exceed the price of the ventilation fix it is standing in for. That is another reason a permanent dehumidifier is a symptom of an unsolved problem rather than a solution.
For landlords: the cost of not fixing it
Set the £400–£1,500 for a proper condensation fix against the alternative: remediation paid for twice when the mould returns, a disrepair claim with damages and the tenant's legal costs once the "lifestyle" argument fails, a council improvement notice forcing the work anyway, and — for social landlords from 30 November 2026 — a cold home that is an Awaab's Law hazard in its own right. Fixing the building once is almost always the cheapest option.
Next steps
Read the full condensation control guide for how the mechanism and the fixes fit together, compare the options in PIV vs MVHR vs extractor fans, or find a verified condensation specialist for a survey and quotes.
Find a verified specialist
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Search the directory →Frequently Asked Questions
- How much does a PIV unit cost to install?
- A PIV unit including installation typically costs £400–£800. It is one of the most cost-effective interventions for condensation mould in a property with loft access. Price varies with loft layout, the PIV variant (some include a heater), and any electrical work required.
- How much does MVHR cost?
- A whole-house MVHR system typically costs £3,000–£8,000 installed. It is significantly cheaper fitted during a refurbishment, when ductwork can be run before rooms are finished, than retrofitted into an occupied home. It is best suited to new build or substantial renovation.
- Is a condensation survey worth paying for?
- Usually yes, if there is any doubt about the cause or the property has had failed fixes before. An independent survey at £200–£400 with a written report tells you whether you are dealing with condensation, rising damp, penetrating damp or something else, and stops you spending four figures on the wrong solution. Be wary of free surveys from contractors who sell the treatment.
- What is the cheapest way to reduce condensation?
- Making sure existing extract fans work and are ducted outside, opening or fitting trickle vents, and keeping heating steady rather than intermittent cost little or nothing. If that is not enough, a PIV unit is the lowest-cost effective whole-home step in a house with a loft.
- Will insurance or a grant cover condensation work?
- Building insurance generally excludes condensation and gradual damp. Some energy-efficiency schemes and local authority programmes can contribute to insulation and heating improvements for eligible households, which also reduce condensation. Availability changes, so check current schemes on GOV.UK and with your local council.