An Approved Ventilation Guide for Builders and Developers
In this blog we discuss how to pass Part F Ventilation Testing first time.
As energy efficiency standards rise, so too does the importance of proper ventilation. Part F of the Building Regulations ensures that new, existing and extended buildings maintain healthy indoor air quality.
But here’s the catch: 60–70% of extract fans fail Part F testing on first inspection. That’s a costly statistic, but one that can be avoided with the right knowledge and planning.
What Is Part F of the Building Regulations?
Part F sets out the legal requirements for ventilation in new buildings. It aims to:
- Ensure a consistent supply of fresh air
- Prevent the build-up of moisture and pollutants
- Reduce the risk of condensation and mould, which can harm both buildings and occupants
The regulations apply to all new builds and major refurbishments, and compliance is mandatory.
How Is Ventilation Testing Carried Out?
Ventilation testing is conducted using a UKAS Calibrated Vane Anemometer, a device that measures airflow in litres per second (l/s). Each extract fan in the property is tested to ensure it meets the minimum airflow rates set out in Part F.
Here’s a quick reference table for intermittent extract (IEV) and continuous extract (MEV) systems:
| Room | Intermittent Extract (IEV) | Continuous Extract (MEV) |
|---|---|---|
| Kitchen | 30 l/s (next to hob), 60 l/s (elsewhere) | 13 l/s |
| Utility Room | 30 l/s | 8 l/s |
| Bathroom | 15 l/s | 8 l/s |
| WC | 6 l/s | 6 l/s |
You can learn more about approved ventilation strategies by clicking here.
Why Do So Many Ventilation Systems Fail?
From our experience, poor ductwork design and installation are the main culprits. Common issues include:
- Kinked or crushed flexible ducting
- Excessive duct lengths (anything over 1.5m can drastically reduce performance)
- Inadequate fan selection, especially axial fans used with long duct runs
Even if a fan is rated for a certain airflow, real-world performance often falls short once installed.
The Cost of Failing Part F
Failing a ventilation test can lead to:
- Delays in project completion
- Costly remedial work
- Re-test fees
In short, it’s far more efficient—and economical—to get it right the first time.
How to Pass First Time
Here’s how to avoid common pitfalls and pass your Part F test with confidence:
- Plan Early
Engage with ventilation specialists during the design phase to ensure your system is fit for purpose. - Choose the Right Fans
For longer duct runs, opt for centrifugal or inline fans instead of axial models. - Keep Duct Runs Short and Straight
Minimise bends and avoid squashing flexible ducting. - Test Before Completion
Consider a pre-test to catch issues early and avoid last-minute surprises.
What’s Next?
Pass Part F Ventilation Testing first time by onboarding with us.
If you’re working on a new build and want to avoid costly delays, our team at Building Compliance Testing is here to help. We offer expert advice, pre-installation planning, and certified Part F testing to ensure your project stays on track.
📞 Contact us today for a free quote or to schedule your ventilation test.