Domakihub How to Install a Bathroom Extractor Fan the Right Way
Cut damp and mould at the source with a properly wired, correctly sized extractor fan.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
Persistent moisture in a bathroom is the fastest route to peeling paint, mould, and structural damage — a particular hazard in the Greek climate where warm, humid summers push condensation into every corner. The video above walks through the complete installation process visually, while this guide breaks it down into clear steps alongside the key decisions you need to make before you start. Whether you are fitting a fan in a private home, a holiday rental, or a hotel en-suite, getting the extraction rate and wiring right from the beginning will save you expensive remediation later.
Why Bathroom Ventilation Matters More Than You Think
A bathroom without mechanical ventilation relies entirely on opening a window — unreliable in winter, impractical in an interior en-suite, and insufficient for the moisture load generated by a hot shower. Over time, unextracted humidity saturates plaster, rots timber window frames, and creates the black mould (Stachybotrys) that is both a health hazard and a costly problem to remediate in rental properties subject to guest reviews.
Greek building regulations align with EU Directive 89/106/EEC and require mechanical ventilation in bathrooms without direct external openings. Even where a window exists, property owners fitting fans in holiday rentals or hotels are protecting their assets and complying with hospitality hygiene standards expected by booking platforms.
Choosing the Right Fan Before You Buy
Fan capacity is rated in cubic metres per hour (m³/h). The standard calculation is room volume multiplied by the required air changes per hour — typically 15 air changes for a bathroom. A 2 m × 2.5 m room with a 2.4 m ceiling has a volume of 12 m³, so you need at least 180 m³/h capacity. Always size up by 20 % to account for duct resistance.
You also need to decide on fan type: axial fans are compact and low-cost but lose performance over long duct runs; centrifugal (radial) fans maintain pressure over longer or flexible ducts and are better for external walls more than 1.5 m away. For bathrooms next to bedrooms in rentals or hotels, choose a low-noise model rated below 30 dB(A). Timer and humidity-sensor models add convenience and energy savings.
How to Install a Bathroom Extractor Fan: 5 Steps
- 1
Plan the duct route and mark the mounting position
Choose a wall or ceiling location as close to the shower or bath as possible — ideally directly above the moisture source. The duct must run to an external wall or terminate in a roof space with an external vent; never duct into a loft void without an exit. Measure the shortest possible duct path, avoiding tight bends that cut airflow. Mark the centre of the fan housing on the ceiling or wall with a pencil.
- 2
Cut the hole and run the duct
Use a hole saw or jigsaw sized to the fan manufacturer's template — typically 100 mm or 125 mm diameter. For a ceiling installation, check above for joists with a joist finder before cutting. Feed a rigid or semi-rigid duct sleeve through to the exterior vent or roof cap, ensuring the duct slopes very slightly downward toward the exit so condensate drains out rather than pooling. Seal the external vent with a louvred cover that closes when the fan is off to prevent back-draught.
- 3
Prepare the electrical supply
In Greece, bathroom electrical work must comply with HD 60364-7-701 (formerly IEC 60364-7-701), which defines moisture zones. Zone 1 (above the bath or shower tray up to 2.25 m) prohibits all accessories except SELV fittings. Zone 2 (the 0.6 m band outside zone 1) allows IPX4-rated accessories. Most ceiling-mounted fans sit in zone 2 or outside both zones. Turn off the relevant circuit at the consumer unit and verify with a non-contact voltage tester. Never work on live wiring.
- 4
Wire the fan and connect to the housing
Most extractor fans are wired into the bathroom lighting circuit so they run with the light, or via a separate fused spur with an in-line timer. Connect Live (brown), Neutral (blue), and Earth (green-yellow) to the corresponding terminals inside the fan — refer to the manufacturer's wiring diagram as timer and humidity models have additional terminals. Use heat-resistant cable where it passes through the duct sleeve. Mount the fan backplate to the ceiling or wall with the screws provided, ensuring the face plate sits flush. Restore power and test before fitting the decorative cover.
- 5
Seal, test, and balance airflow
Apply a thin bead of neutral-cure silicone sealant around the fan faceplate where it meets the tile or ceiling surface to prevent damp air bypassing the fan and entering the ceiling void. Switch the fan on and hold a tissue near the grille — it should be drawn firmly toward the fan. Check the external vent louvres open under airflow and close fully when the fan stops. Run the fan for 10 minutes with the bathroom door slightly ajar (a 10 mm gap at the door bottom provides make-up air); if the door slams shut, make-up air is insufficient and you should add an undercut or transfer grille.
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FAQ
- Do I need an electrician to install a bathroom extractor fan in Greece?
- Greek law (Presidential Decree 108/2013) requires that fixed electrical installations, including new bathroom circuits and spurs, are carried out or supervised by a licensed electrician who issues a Responsible Electrician's Declaration (Υπεύθυνη Δήλωση Εγκαταστάτη). Connecting a plug-in fan to an existing outlet is different, but any new fixed wiring or circuit modification must be certified. For rental properties this certificate is also required by AADE for short-term rental registration.
- What extraction rate do I need for a small bathroom?
- Use the formula: room volume (m³) × 15 air changes per hour, then add 20 % for duct resistance. A typical 6 m² bathroom with a 2.4 m ceiling needs roughly 216 m³/h. When in doubt, choose the next size up — an oversized fan running on a timer costs less than mould remediation.
- Can I duct a bathroom fan into the ceiling void instead of outside?
- No. Ducting into a closed ceiling or loft void transfers moist air into the building structure, which causes timber rot and mould in the roof space — often worse than the original bathroom problem. The duct must terminate outside the building through an external wall vent or a roof tile vent with a bird guard. This is also a building regulation requirement under the Greek Energy Performance of Buildings framework (KENAK).