Positive input ventilation (PIV)
Loft or wall units that gently push filtered air into the home to tackle condensation.
From £795 inc VAT per home
Condensation, mould and landlords
Ventilation fixes for condensation and mould
We find why the house is wet and fix the ventilation, rather than painting over mould.
- From £445 inc VAT per fan
- Free survey on the UK mainland
- Airflow tested and recorded
Condensation forms when warm, moist indoor air meets a cold surface, and if it keeps happening, black mould follows. Most of the moisture comes from everyday life: showers, cooking, drying clothes and breathing. We measure humidity and airflow, find where the moisture is coming from and why it is not getting out, and fix the ventilation.
How it works
A typical family puts several litres of water into the air every day. If extract fans are weak, ducted into the loft or switched off, and windows stay shut in winter, that moisture settles on the coldest surfaces: window reveals, external corners, behind wardrobes and on bathroom ceilings. Mould needs that damp surface to grow.
Ventilation is usually the biggest part of the cure, but not the only part. Heating patterns, insulation gaps and cold bridges matter too, and some damp is not condensation at all: leaks, penetrating damp and rising damp need different trades. We tell you if that is what we find rather than selling a fan that will not help.
Options we fit
Survey and findings
Humidity and surface readings, existing fans flow-tested, and a written list of causes and fixes.
Fan upgrades
Weak or loft-vented fans replaced and ducted outside, with humidity control.
Whole-home ventilation
PIV, continuous extract or MVHR where moisture is spread through the house.
Mould treatment advice
How to clean and treat affected areas once the cause is fixed.
Signs you need this
- Black mould on window reveals, ceilings or behind furniture
- Water running down windows on cold mornings
- Musty smell in bedrooms or wardrobes
- Peeling paint or wallpaper in bathrooms
- Damp patches that dry out in summer and return in winter
- Someone in the home with asthma or allergies made worse by damp
Guide prices
| Work | Guide price |
|---|---|
| New ducted fan to outside through the loft or ceiling (insulated duct, roof or soffit outlet) (per fan) | £445–£745 inc VAT |
| Positive input ventilation (PIV) loft unit, supplied and fitted (per home) | £795–£1,395 inc VAT |
| Continuous-running extract fan (dMEV) with humidity boost, flow tested (per fan) | £345–£595 inc VAT |
| Condensation and mould ventilation survey with written findings (per home) | £125–£225 inc VAT |
Guide prices using West Midlands (our baseline) rates. Home prices include VAT at 20%; business prices exclude VAT. A guide price is not a quote: we confirm a fixed price in writing first. London is about 20% higher and the North East about 8% lower.
What happens, step by step
Survey
Humidity, temperature and surface readings; extract fans flow-tested; loft and ducts checked.
Find the cause
We separate condensation from leaks, penetrating or rising damp, and tell you which trade fixes what.
Recommend
A written plan, cheapest effective fix first, with fixed prices.
Fix
Fans, PIV, dMEV or MVHR fitted and tested.
Check back
We can log humidity afterwards so you can see the difference.
The rules that apply
England
In England, ventilation is covered by Part F of the Building Regulations and its guidance, Approved Document F (2021 edition). Serious damp and mould is a hazard under the Housing Health and Safety Rating System, and social landlords now have fixed timescales under Awaab's Law.
Wales
Wales has its own Part F ventilation guidance, published by the Welsh Government, and work is checked by building control. Rented homes in Wales must be fit for human habitation under the Renting Homes (Wales) Act, and damp and mould is one of the matters considered.
Scotland
In Scotland, ventilation is covered by the Building (Scotland) Regulations and section 3 of the Technical Handbooks, and most building work needs a building warrant first. Scottish rented homes must meet the Repairing Standard (private) or the Scottish Housing Quality Standard (social), which cover damp.
Northern Ireland
In Northern Ireland, ventilation is covered by the Building Regulations (Northern Ireland) and Technical Booklet K. Landlords in Northern Ireland have repairing and fitness obligations that cover serious damp.
Questions people ask
What is the main cause of condensation in a house?
The main cause is moisture from everyday living, such as showers, cooking and drying clothes, that is not being extracted, combined with cold surfaces where it condenses. Poor or failed extract fans are a very common cause.
Will a dehumidifier fix condensation?
A dehumidifier helps in one room but treats the symptom. Fixing the extract in the wet rooms, and adding whole-home ventilation where needed, removes moisture before it spreads.
Is black mould dangerous?
Damp and mould can affect health, particularly for people with asthma, allergies, weak immune systems, children and older people, according to NHS and government guidance. It should be dealt with rather than lived with.
Is PIV or MVHR better for condensation?
For most existing homes with general condensation, PIV plus good extract fans is the most cost-effective fix. MVHR suits airtight, well-insulated homes and full renovations.
How much does a condensation survey cost?
A ventilation survey with written findings costs £125 to £225 including VAT. If we are surveying for an installation we quote for, the survey is free.
Can you tell if it is rising damp?
We can tell you when the pattern does not look like condensation, such as a tide mark low on a wall or damp that appears after rain, and point you to the right specialist.
Related services
Extractor fan installation
Bathroom, kitchen and utility fans sized to the Part F rates, ducted outside and tested.
From £175 inc VAT per fan
Ventilation for landlords and letting agents
Tested fans and PIV for rental homes and HMOs, with records for your property file.
From £1,495 inc VAT per property
Indoor air quality surveys
CO2, humidity and particulates logged for a week, with plain-English findings.
From £145 inc VAT per home
Read before you buy
Condensation and mould ventilation fixes by area
Choose your area for local guide prices and the towns we cover.
- Bedfordshire
- Berkshire
- Bristol
- Buckinghamshire
- Cambridgeshire
- Cheshire
- Cornwall
- Cumbria
- Derbyshire
- Devon
- Dorset
- County Durham
- East Riding of Yorkshire
- East Sussex
- Essex
- Gloucestershire
- Greater London
- Greater Manchester
- Hampshire
- Herefordshire
- Hertfordshire
- Isle of Wight
- Kent
- Lancashire
- Leicestershire
- Lincolnshire
- Merseyside
- Norfolk
- North Yorkshire
- Northamptonshire
- Northumberland
- Nottinghamshire
- Oxfordshire
- Rutland
- Shropshire
- Somerset
- South Yorkshire
- Staffordshire
- Suffolk
- Surrey
- Tyne and Wear
- Warwickshire
- West Midlands
- West Sussex
- West Yorkshire
- Wiltshire
- Worcestershire
- Clwyd
- Dyfed
- Gwent
- Gwynedd and Anglesey
- Mid Glamorgan
- Powys
- South Glamorgan
- West Glamorgan
- Edinburgh
- Lothians
- Glasgow
- Lanarkshire
- Renfrewshire and Inverclyde
- Dunbartonshire
- Ayrshire
- Fife
- Forth Valley
- Tayside
- Aberdeen and Aberdeenshire
- Highland and Moray
- Dumfries and Galloway
- Scottish Borders
- Argyll and Bute
- Scottish Islands
- County Antrim
- County Armagh
- County Down
- County Fermanagh
- County Londonderry
- County Tyrone
Get a guide price in two minutes
Answer a few questions for a price range, or send photos and we will come back to you with a written quote.