Damp and moisture meters
Do trickle vents, together with paint, count as evidence on mould that sealing the vents can worsen, or only as a note of what was visible?
Painted vents are not a mould test on their own. Trickle vents and paint on or over them were seen. They are not a measurement of what happens if the vents are sealed. Trickle vents are the small background openings in many windows. Paint can clog or close them. The survey recorded that condition. It has not measured humidity, has not proved a mould mechanism and has not tested the ventilation of the room.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
Background vents let a trickle of fresh air through a window head even when the window is shut. If paint seals the slot, that path is reduced. Rooms then rely on other opening lights, extract fans and how people use them. Moisture from cooking and bathing can stay longer and condense on cold surfaces, and mould feeds on that damp. This visit did not measure that chain. It saw paint and vents. The worsening is a risk to understand, not a result already logged.
Tell the solicitor the vents were noted painted, not proved as the cause of any mould. Freeing a painted vent is a small building job for whoever you instruct later, not a finding of this survey. Keep extract fans and how the rooms are used as separate questions. Tell a lender the survey did not measure indoor moisture and did not test a ventilation rate. Paint on a vent is a note, not a mould certificate.
What should you ask your surveyor?
- Were the trickle vents seen painted, rather than flow-tested?
- Has mould been left without a measured cause?
- Did this visit avoid testing the ventilation rate?
What are the typical next steps?
- Treat painted trickle vents as a visual note.
- Tell the solicitor they were not proved to be the mould cause.
- Do not tell a lender a ventilation rate was measured.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Does opening the window once on a viewing clear condensation risk?
No. One open window on a dry visit is not how the house is lived in. The survey saw trickle vents and paint. It did not measure humidity and did not test ventilation. Condensation depends on moisture produced indoors and on the paths left for air. A viewing does not reproduce a winter evening.
Are trickle vents the same as an extract fan in the bathroom?
No. Trickle vents are small inlets, usually in window frames. An extract fan is a powered outlet in a wet room. Paint on a vent does not describe the fan, and this survey did not test either device's performance. Note them separately. A fan that exists on the ceiling was not proved by a painted slot in the window.