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Why Is My PIV Unit Not Stopping Condensation?
If you've had PIV fitted and the windows are still wet, it's worth checking what's actually happening before deciding the unit doesn't work. The PIV might be doing it’s job, but another part of your ventilation system is not.
Here at ClearAIR, we focus on practical advice and thorough assessments to establish a suitable loft-mounted domestic PIV solution. Here's what matters before you write your PIV off as simply ‘not working’
Check Whether the Unit Is Running
PIV is normally designed to provide continuous background airflow. Check that the system is operating and hasn't been switched off or obstructed.
Start with the power supply and any visible fault indicators before changing the system settings..
Look at Other Moisture Sources
Showers, cooking, clothes drying and poor wet-room extraction can create more moisture than the home is dealing with. A PIV unit won't fix a leaking pipe or penetrating damp either.
An extractor that doesn't clear bathroom steam can leave the home with more moisture than expected..
Think About Airflow Through the House
Closed or blocked ventilation routes and poor diffuser positioning can affect performance. The loft air source and system settings also need to be appropriate.
Filters and diffusers need to stay unobstructed so the intended airflow isn't restricted..
Don't Forget Cold Surfaces
Very cold glazing, poorly insulated corners and thermal bridges can still attract condensation even when ventilation improves. Heating and building condition matter too.
Cold window reveals may still need attention even after indoor humidity improves..
When to Ask for a Check
If condensation persists, record where and when it happens and contact your installer. A proper review is better than turning the fan to maximum or assuming a replacement unit is needed.
A note of weather, room temperature and the affected windows gives an installer something useful to investigate..
Speak to ClearAIR
If you've already got a PIV unit but you're still struggling with condensation, tell us what system you've got, how long it's been running and where the moisture is appearing. We'll help you work out what might be going wrong and whether it's the unit, the ventilation or something else causing the problem..
Frequently asked questions
There's no guaranteed number of days. Some people notice fresher air or less window condensation fairly quickly, but results depend on moisture production, temperature and whether other ventilation problems remain..
Generally, yes. PIV is intended to provide continuous background ventilation, so switching it off for long periods can undermine the benefit..
Yes. Dirty or blocked filters can restrict airflow and reduce performance. Check the maintenance instructions for your specific model before attempting any work..
Cold glazing, high indoor humidity, poor extraction or inadequate airflow can still cause condensation. Check where and when it happens rather than simply turning the PIV fan up..
Yes. A roof or plumbing leak can leave damp patches that may be mistaken for condensation. If staining follows rain or stays wet in one area, investigate the building defect..
More on How PIV works
Do PIV Units Actually Work?
PIV can make a noticeable difference in the right home. The key words there are 'the right home' because not every patch of damp is a ventilation problem.
Read article
What Are the Advantages and Disadvantages of PIV Systems?
PIV has some real advantages, but it also has limits. Knowing both is a much better starting point than being told it's the answer to every damp problem.
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