UK cost guide
How much does it cost to fix condensation in a UK home?
Condensation fixes range from changes that cost nothing, such as ventilation habits and heating patterns, to installed measures such as extractor fans, trickle vents and insulation. Each installed measure is quoted separately by a tradesperson, so get written quotes and start with the cheapest change that addresses the actual moisture source.
Most UK condensation problems solve at the low end of this range if you address ventilation, cold bridging and moisture generation together. A PIV unit is a good tool, not a magic wand — fitting one over a damp lifestyle without a hygrometer wastes both.
Last updated Reviewed by Vincent Pamenter
Cost breakdown — UK 2026
Ask for an itemised written quote for your property. Confirm VAT, access, structural repairs and hazardous-material handling before agreeing to work.
From free changes to installed measures
Hygrometer + behaviour changes
- Price basis (UK 2026)
- Written quote required
- What moves the price
- Free once you own the meter. Effect depends on discipline.
Humidistat bathroom extractor (replacement)
- Price basis (UK 2026)
- Written quote required
- What moves the price
- Fan spec, ducting run, wall vs ceiling, wiring.
New bathroom extractor with duct run
- Price basis (UK 2026)
- Written quote required
- What moves the price
- New duct route, external grille, plastering.
Kitchen extractor (external-vented)
- Price basis (UK 2026)
- Written quote required
- What moves the price
- Long duct runs, external grille, cabinets to work around.
PIV loft unit (positive input ventilation)
- Price basis (UK 2026)
- Written quote required
- What moves the price
- Unit spec, loft access, filter grade, warranty.
Whole-house MEV / MVHR retrofit
- Price basis (UK 2026)
- Written quote required
- What moves the price
- Duct routes, unit spec, commissioning; usually a renovation-only option.
Trickle vent retrofit (per window)
- Price basis (UK 2026)
- Written quote required
- What moves the price
- Frame type; some UPVC frames don’t accept retro-fit vents.
Stop The Mould does not publish price ranges it has not verified. Every figure on this page is either free at the point of visit or our own published pricing; everything else needs a written, itemised quote for your property.
What drives the price up or down
Condensation is a ventilation and thermal problem, so most cost variation is about how far the ductwork must run, how cold the coldest wall is, and how many people generate moisture in the home.
Pushes price up
Long duct runs
A bathroom fan on an internal wall with a 6 m external duct doubles the labour vs a fan on an external wall.
Pushes price up
Solid-wall Victorian property
Cold-bridge corners need modest internal insulation or lifestyle changes to keep surface temperatures above dew point — otherwise ventilation alone fights the physics.
Pushes price up
Occupancy density
More occupants = more moisture. Two-bed flats with four people need higher extract rates than the same flat with two.
Brings price down
External-wall bathroom
Short duct run + external grille = the cheapest and highest-performing extractor install.
Brings price down
Existing wiring in place
Replacing an old fan on existing wiring saves the electrician.
Pushes price up
Listed / conservation area
External grilles may need conservation consent, adding time and paperwork.
Brings price down
Room-by-room approach
An extractor fan often ends the problem in one room. Fitting a PIV before trying the fan is putting a whole-house tool onto a single-room problem.
Pushes price up
MVHR retrofit without renovation
Retrofitting mechanical ventilation with heat recovery outside of a wider refurbishment is expensive per m² — often not worth it as a standalone.
Cheaper-first alternatives
Almost every UK condensation problem responds to a properly-sized extractor and a hygrometer before any bigger kit is needed. Try the small spend first.
Bedroom condensation + streaming windows
Record humidity and ventilation conditions. Ask an assessor whether ventilation improvements or investigation of another moisture source are needed.
Bathroom ceiling mould
A humidistat extractor with a proper duct is usually the entire solution. PIV is unnecessary.
Cold-corner mould behind wardrobe
Airflow gap + insulation to the cold spot resolves this; PIV alone won’t raise the wall’s surface temperature.
Kitchen steam damp
A properly-vented externally-ducted extractor with lids-on cooking is cheaper than any structural fix.
Regional variation, multiple quotes, and red flags
Prices vary by region, by trade and by how far a surveyor or contractor has to travel. Rather than relying on a national average, get two or three written quotes for your property and compare what each one actually includes.
Ventilation quotes should specify the extract rate (l/s), the duct length and diameter, the unit make and model, and whether it is humidistat-controlled. If it doesn’t, you are quoting on faith.
Red flag
PIV recommended without a hygrometer reading
No installer can know if PIV is the right tool without measuring current humidity. It is often oversell.
Red flag
Extractor spec not listed
A quote without a spec cannot demonstrate compliance.
Red flag
Kitchen extractor recirculating (no duct)
A recirculating fan does not remove moisture from the room. In a damp kitchen, that is essentially useless.
Red flag
Claim that PIV cures rising damp
PIV addresses condensation. It does not fix rising, penetrating or leak-related damp.
Red flag
One-visit ‘cure’ without behavioural change
No fitted kit can beat continuous moisture generation. If the quote promises a cure without any behavioural conversation, that’s marketing.
PIV, MEV, MVHR — what actually differs
PIV (positive input ventilation) pushes filtered air from a loft or hallway unit into the home, gently over-pressurising it so moist air leaves via natural gaps.
MEV (mechanical extract ventilation) extracts continuously from wet rooms via central ducting.
MVHR (mechanical ventilation with heat recovery) balances supply and extract and recovers heat from outgoing air. Excellent in airtight new-build/retrofit-to-Passivhaus contexts.
The hygrometer test: the cheap diagnostic that changes what you spend
Humidity readings can add context, but cannot on their own distinguish a ventilation problem from a cold surface, a leak or another cause. Record conditions over time and ask an independent assessor to interpret them alongside the property inspection.
This single reading determines whether the answer is an extractor fan or a whole-house positive input ventilation unit, and it prevents unnecessary PIV installs.
Before you spend anything
Before spending anything on ventilation kit, buy a hygrometer and log readings for a week. A Free Case Check on the affected room lets us tell you whether ventilation is the primary lever or whether the fix is thermal — commonly a cold-bridge insulation or a heating-pattern change.
This is general information, not medical advice. If you're worried about your health, contact your GP or NHS 111.
This is general information, not legal advice. For advice on your specific situation, contact Shelter, Citizens Advice, or a solicitor.
Cost FAQs
Will a PIV unit really cure condensation?
In leaky, older UK homes with condensation-pattern mould in multiple rooms, PIV is usually a good tool. In a single-room bathroom problem, a proper extractor is a better fit at a fraction of the cost.
Do I need Building Regulations approval to fit a fan?
Fan installs in the same room and vent position are generally like-for-like replacements. New extract points, new external grilles or altered ductwork can fall under Part F and Part J — a competent installer will sign off.
Are dehumidifiers worth it?
As a short-term aid during a wet spell or after a leak, absolutely. As a permanent replacement for ventilation, no — they treat symptoms only and add to your electricity bill.
Do trickle vents work?
Yes, when they are open. A closed trickle vent is a shelf. Building Regulations for new windows now typically require trickle vents; retrofits vary by frame.
How quickly should condensation improve after a fan install?
Reported symptoms (streaming windows, bathroom fog) usually improve within days. Wall staining and mould scars need cleaning after the ventilation is in place.
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