Particularly in the colder months, I get questions about foggy bathrooms. Here’s a brief run-down of the typical answers I provide.
Modern bathrooms produce high levels of moisture during normal use, particularly when showering. Managing this moisture effectively is essential to prevent condensation, mirror fogging, and long-term issues such as mould growth.
Why ventilation alone isn’t enough
Exhaust fans remove moisture from the air, but when a bathroom starts off cold, warm moist air from a shower can quickly condense on cooler surfaces like mirrors, tiles, and glass. This is what causes visible “steam” and fogging, even when the fan is running.
The role of heating
Heating the bathroom (via a ducted outlet or heat lamp) raises both air and surface temperatures. This helps prevent condensation forming in the first place, keeping mirrors clearer and reducing surface moisture. Warm air holds more moisture than cold air does.
The role of continuous ventilation
Your home can be fitted with a 24-hour exhaust system (such as a Panasonic continuous fan). These systems:
- Run continuously at a low level to manage background moisture
- Run at full capacity during bathroom use to remove high levels of humidity
- Run-on at full capacity for 15 minutes after use to clear bulk airborne moisture
- Continue clearing residual bathroom & household moisture (24hr mode)
This approach helps keep the home dry over time, even after moisture-producing activities have finished. We specify this type of mechanical ventilation as minimum in outGold Star standard specification.
Best practice for optimal performance
For the best results, we recommend:
- Turning on bathroom heating during showers
- Turning the exhaust fan on while showering. This will –
- Allow the 15-minute run-on timer and 24hr mode to reduce moisture load
Summary
Heating helps prevent condensation at the source, while continuous ventilation removes moisture over time. Both are essential components of an effective moisture management strategy.