Ventilation
testing.

What I test

Ventilation testing measures how much air the installed system actually moves. I carry it out as part of a retrofit assessment: when a building is being insulated, draughtproofed or otherwise tightened, the ventilation has to keep pace — or you build a moisture and air-quality problem into the fabric. Measuring the background ventilation gives the retrofit design a real baseline to work from, and a way to check the result afterwards.

To be clear on scope: this is domestic background ventilation testing for retrofit purposes. I don’t issue the Approved Document F compliance certificates that Building Control require for new-build sign-off — if that’s what you need, you’ll want a commissioning engineer who certifies to Part F.

When it’s useful

• Whole-dwelling retrofit — particularly where airtightness is being improved (insulation, draughtproofing, new windows). Tightening the envelope without checking ventilation is the single most common cause of post-retrofit damp and indoor-air-quality complaints.
• Before and after fabric work — a baseline measurement before the work and a check afterwards confirms the ventilation still performs once the building is tighter.
• Diagnosing damp or condensation — where an existing home is suffering moisture problems, measuring what the ventilation is actually doing is often the first useful step.

Systems I can test

• System 1 — intermittent extract. Bathroom and kitchen extract fans, plus background ventilators. Each extract point measured; trickle vents inspected and recorded.
• System 2 — passive stack ventilation. Less common in modern stock; measured where present.
• System 3 — continuous mechanical extract (MEV). A central or decentralised continuous extract system. Measured at each terminal.
• System 4 — mechanical ventilation with heat recovery (MVHR). Supply and extract terminals measured; boost rates checked.

What happens on site

I measure the airflow at each extract point and terminal with a Testo 417 vane anemometer, logging each reading against its location, the system mode and the conditions on the day. The visit takes between 60 minutes and three hours depending on the size of the property and the system installed.

Where a system is clearly underperforming I’ll point to the likely cause — ducting kinks, terminal balancing, fan setting, blocked filters — so it can be put right before the retrofit is signed off.

What you’ll get

The measured airflow figures with a plain-English summary, feeding into the retrofit assessment and improvement plan. This is measurement and diagnosis to inform the retrofit — not a Building Control compliance certificate.