There’s no fixed rule, but if you’re seeing ongoing condensation or mould, it’s worth having the fan checked properly.
Sep 30, 2026 Extractor Fan Installation Are trickle vents (window vents) enough to stop condensation? gazza
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Aug 28, 2026 Extract Fan Servicing & Maintenance “I’ve Got a Bathroom Fan… So Why Am I Still Getting Mould?” gazza