One of the most common pieces of advice given to homeowners is:
"Just open your windows."
Whilst improving ventilation can certainly help, many homeowners are frustrated to find that they're already opening windows every day and still waking up to condensation on the glass, black mould around window frames or damp patches on external walls.
So, why isn't it working?
The answer is that condensation is influenced by more than just fresh air.
Temperature, humidity, insulation, occupancy and ventilation all play a role.
Quick Answer
Opening windows can help reduce moisture levels, but it isn't always enough to prevent condensation. If excess humidity is continually being generated or ventilation is inadequate elsewhere in the property, condensation may persist despite regularly opening windows.
Why Doesn't Opening A Window Always Work?
Ventilation is only one part of the solution.
Other factors include:
- High indoor humidity
- Cold external walls
- Poor insulation
- Drying clothes indoors
- Inadequate extractor fans
- Occupancy levels
- Restricted airflow
A briefly opened window may not remove enough moisture to significantly reduce condensation.
Everyday Activities Add Moisture
Many homeowners underestimate how much water is released into the air each day.
Examples include:
- Cooking
- Showering
- Bathing
- Drying washing indoors
- Breathing while sleeping
Without effective ventilation, this moisture accumulates inside the property.
The Importance Of Continuous Ventilation
Rather than relying solely on opening windows, some homes benefit from continuous ventilation systems that help manage humidity levels throughout the day.
Depending on the property, this could include:
- Positive Input Ventilation (PIV)
- Decentralised Mechanical Extract Ventilation (DMEV)
- Improved extractor fans
- Better sub-floor ventilation where appropriate
The most suitable solution depends on the property and the cause of the moisture.
What We See During Surveys
It's common for homeowners to tell us:
"We open the windows every day, but the mould keeps coming back."
In many cases, the issue isn't a lack of effort. It's that the property needs a more effective long-term ventilation strategy.
About The Author
Written by Connor Saunders
Connor Saunders is an FODCS Certified Surveyor with a particular interest in condensation, ventilation and indoor air quality.
Technical Review
Reviewed by Aaron Worrall
Aaron Worrall is Director of Weather Wise Solutions, CSTDB-qualified surveyor, ABBE Level 3 Award in Dampness in Buildings holder, FODCS Certified Surveyor, Tech.DEW qualified professional and Advanced City & Guilds Mould Remediation specialist.
Contributor
Ryan Loughrie
Ryan Loughrie is an FODCS Certified Surveyor with practical experience installing ventilation systems and resolving condensation-related issues.
Frequently Asked Questions
Why do I still get condensation if I open my windows?
Other factors such as humidity, insulation and ventilation design may be contributing.
Does opening windows stop mould?
It can help, but it won't resolve mould if excess moisture remains.
Should windows stay open all day?
Not necessarily. Effective ventilation should be balanced with comfort and energy efficiency.
Is condensation worse in winter?
Yes. Cold external temperatures make condensation more likely.
Can ventilation systems help?
Yes. Systems such as PIV and DMEV can help manage humidity where appropriate.
References & Further Reading
- Approved Document F: Ventilation – https://www.gov.uk/government/publications/approved-document-f-volume-1-dwellings
- UK Health Security Agency – https://www.gov.uk/government/publications/damp-and-mould-understanding-and-addressing-the-health-risks-for-rented-housing-providers
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