Choose a bathroom extractor fan by checking the duct size, the airflow it can deliver through your duct, the controls and the electrical location. Confirm the route to outdoors and the mounting position before you buy.

Check whether you are replacing a fan or planning a new route

For a replacement, photograph the fan label, measure the accessible opening and ask where the duct terminates. For a new installation, ask the installer to work out the route, bends and outdoor outlet before choosing a model. A fan with the same faceplate size can still have a different duct connection.

Choose the duct size and check airflow

Our 100 mm versus 150 mm guide explains what to measure. Compare the fan data in the same units, then ask about the airflow through the installed duct. In England, use the edition of Approved Document F that applies to your work. For projects elsewhere in the UK, ask about the local requirements.

Choose how the fan starts and stops

A run-on timer keeps the fan going for a set period after its trigger switches off. A humidistat responds to the humidity around its sensor. Check the exact operating modes and settings in the instructions. See the timer and humidity-sensor comparison.

Compare noise and confirm the bathroom location

Compare dB(A) figures at equivalent distances and modes. Ask about vibration and duct noise as part of the installation. Use a registered electrician to check bathroom zones, the model’s rating and isolation before fitting or replacing a fan.

What to have ready before you order

Keep the existing fan model, proposed duct diameter and route, the mounting position, and your preferred control type. Ask whether the installer will check airflow once fitted. If persistent damp remains despite working ventilation, ask someone to investigate other sources of moisture.

Compare the 100 mm run-on timer fan and 150 mm humidity-sensor fan in our bathroom extractor fan range. Check the product specification with your installer before ordering.

Frequently asked questions

Can I choose a fan just by bathroom size?

Room size is useful context. Also check the applicable ventilation requirements, installed airflow, duct route and fan location.

Read the supporting guides

Sources