Bathroom Extractor Fan in 2026 — Complete Guide: Airflow Calculation, What Separates the Models and What to Buy Without Regret

Mould on the ceiling or on shower sealant? Mirror steamed up minutes after a shower? Persistent smell that doesn't go away when you open the door? These are all symptoms of the same problem: bathroom ventilation is not working — either it doesn't exist, or the installed fan is undersized or poor quality. This guide explains exactly how to calculate the airflow you need, what separates a good fan from a cheap one, and which models are worth the money in 2026.

Why bathroom ventilation matters more than you think

A 6 m² bathroom in which you take a 10-minute shower produces approximately 150–200 ml of evaporated water into the air. Without active extraction, this humidity deposits on cold surfaces — ceiling, exterior walls, window glass, silicone sealants. Mould begins forming within weeks under conditions of repeated humidity above 70%.

The consequences are both aesthetic and health-related: mould spores (particularly Stachybotrys and Aspergillus) are associated with respiratory allergies, irritation and, in prolonged exposure, chronic lung conditions. For people with asthma or allergies, a bathroom without adequate ventilation is a genuine risk factor.

Opening a window is not a solution: in apartment blocks, the bathroom window typically opens onto a light well or directly onto the street. In winter, aggressive airing cools the room and creates thermal shock. The correct solution is an extraction fan connected to the building's ventilation stack or a wall sleeve through to the exterior.

Step 1 — Calculate the airflow you need

Before anything else, calculate the required airflow. The formula is straightforward:

Q (m³/h) = Bathroom area (m²) × ceiling height (m) × air changes per hour

For residential bathrooms, standard I5-2022 recommends at least 8 air changes per hour (compared to 6 for normal spaces), precisely because bathrooms produce intense and intermittent humidity.

Practical examples

Practical rule: if the bathroom has a shower or bath, add 20–30% to the calculated airflow to cover the humidity peaks produced during a hot shower.

👉 Airflow calculator — check for your bathroom

Step 2 — Understand the real difference between models

The market is flooded with bathroom fans at 20–40 euros. Before buying the cheapest available model, it is worth understanding exactly what you are paying for — and what you are not.

What cheap fans are missing

Noise. Entry-range fans (generic brands) are loud at rated airflow — above 35–40 dB(A). This sounds like a hairdryer at medium distance. A premium Casals fan operates at 26–32 dB(A) — imperceptible from the bedroom, barely audible from the bathroom with the door open.

Service life. Cheap bearings fail in 3–5 years. Casals models use self-lubricating bearings rated for 40,000+ hours of operation (equivalent to 15–20 years at normal use). A bathroom fan mounted in a false ceiling or a tiled wall is difficult to replace — the wrong initial choice means a partial renovation later.

Backdraft damper. Without a backdraft damper (or with a poorly sealing plastic one), the building's ventilation stack or outside wind can push air back into the bathroom — cold air in winter, neighbours' smells year-round. Casals models have an integrated backdraft damper with complete sealing.

Moisture protection. A bathroom is a wet environment. Fans without IPX4 certification (protection against water splashing) are not technically compliant with installation standards for wet rooms. All Casals models carry IPX4 certification.

Motor warranty. Premium brands offer 2–5 year motor warranties with spare parts available. With generic brands, a failure after 2 years means replacing the entire fan.

What you get with a Casals fan versus a generic fan at 20 euros

Price difference: 50–80 euros. Additional service life: 10–15 years. Annual cost of the difference: 4–6 euros — less than a coffee per month.

Step 3 — Timer or humidity sensor? Which option suits you

This is the decision most frequently made incorrectly.

Basic (no automation)

The fan runs when the light is on and stops when it is off. Simple, lower cost, but with one fundamental problem: the humidity produced during a shower is not fully evacuated while the shower is running. The greatest quantity of vapour rises in the minutes after the water stops — and at that point the lights are already off. Result: humidity remains and deposits.

When to choose it: for service bathrooms or WCs without a shower where humidity is not a major issue.

Timer (run-on)

The fan starts with the light and continues to run for a preset time (3–20 minutes) after the light is switched off. This is the correct standard for any bathroom with a shower or bath — you evacuate residual humidity after leaving the bathroom.

When to choose it: any bathroom with a shower or bath. The optimal solution for the price-to-effectiveness ratio.

👉 Casals Erelis 150 T — 340 m³/h, 17mm ultra-slim panel, integrated timer 👉 Casals Tekstur 120 T — 180 m³/h, paintable textured panel, 3–20 min timer

Humidity sensor

The fan activates automatically when relative humidity in the bathroom exceeds the set threshold (typically 70–80% RH) and stops when humidity drops below it. Independent of the light — activates even from a slow leak or damp clothes left in the bathroom.

When to choose it: for bathrooms with heavy use (large families), bathrooms in rental properties (you cannot rely on tenants to use a switch), or any bathroom where fully automatic operation without any manual intervention is required.

Tip: the ideal combination is timer + humidity sensor — timer for rapid post-shower evacuation, sensor for continuous monitoring. Casals models with the HR+T suffix include this combination.

Step 4 — Wall or ceiling mount? Ø100, Ø120 or Ø150 mm?

Duct diameter

The diameter is determined by the required airflow and the existing installation:

• Ø100 mm — for airflows up to ~100 m³/h, small bathrooms (4–5 m²)
• Ø120 mm — for airflows 100–200 m³/h, medium bathrooms (5–7 m²)
• Ø150 mm — for airflows 200–350 m³/h, large bathrooms or combined bathroom+WC

Important: if you have an existing Ø100 mm duct and install a Ø150 mm fan with an adapter, you will lose 40–60% of the rated airflow. The smallest diameter in the system dictates actual performance.

Wall vs. ceiling

Wall mounting — the standard solution. The fan mounts on the external wall of the bathroom, with a sleeve directly to the exterior. Most efficient and simplest to install. Applicable where the bathroom has an available exterior wall.

Ceiling mounting — for internal bathrooms without an exterior wall (common in apartment blocks). The fan mounts in the ceiling with a duct to the building's ventilation stack or a horizontal duct reaching the exterior. Requires verifying that the building stack is functional and unobstructed.

Recommended models from ventilation.ro — complete comparison

All Casals models on ventilation.ro are manufactured in Spain, with self-lubricating bearings, integrated backdraft damper, IPX4 and motor thermal protection. Full CE documentation.

Casals Tekstur 120 T — for bathrooms where design matters

Airflow: 180 m³/h | Duct: Ø120 mm | Timer: 3–20 min adjustable Distinguishing feature: double textured front panel that can be painted in any colour — disappears completely into the bathroom wall. The most discreet fan in the range visually. Ideal for quality renovations where a visible grille breaks the finish.

👉 Casals Tekstur 120 T — view price and availability

Casals Erelis 150 — for bathrooms where silence is the priority

Airflow: 340 m³/h | Duct: Ø150 mm | Front panel: 17 mm ultra-slim Distinguishing feature: 17 mm front panel — the thinnest in its category. Sits completely within the thickness of a false ceiling or tiled wall without protruding. Geometrically optimised for minimum noise. Eco-friendly with recycled materials.

👉 Casals Erelis 150 basic — without timer

Casals Erelis 150 T — the complete solution for the bathroom with a shower

Airflow: 340 m³/h | Duct: Ø150 mm | Integrated run-on timer Distinguishing feature: same specifications as Erelis 150, with the addition of the run-on timer — continues ventilating after the light is switched off. Our primary recommendation for any bathroom with a shower or bath.

👉 Casals Erelis 150 T — with timer

Casals Lidero 150 — solid performance at an accessible price

Airflow: 340 m³/h | Duct: Ø150 mm | Backdraft damper: automatic gravity Distinguishing feature: the best value-for-money Casals option in the range. The same core technical specifications as the Erelis, with a standard panel (not ultra-slim). Available with timer and with humidity sensor+timer.

👉 Casals Lidero 150 — basic version

Casals Kubalik 230 — for reversible wall/window ventilation

Airflow: 450 m³/h | Mounting: exterior wall or window | Reversible: extract or supply Distinguishing feature: operates in both directions — extraction or fresh air supply. Automatic backdraft damper. Ideal for bathrooms with direct access to the exterior wall, where both extraction and controlled natural fresh air supply are wanted. High airflow — suited for large bathrooms or combined bathroom+dressing room.

👉 Casals Kubalik 230 — 450 m³/h reversible

Common mistakes when choosing and installing a bathroom extractor fan

Mistake 1 — Choosing by price, not airflow The cheapest Ø100 mm fan delivers 80–95 m³/h. In an 8 m² bathroom, this achieves only 3–4 air changes per hour against the recommended minimum of 8. The humidity problem doesn't disappear — it moves from the shower itself to the bathroom surfaces.

Mistake 2 — Connecting to the light and considering the job done A fan without a timer stops when the light is switched off, exactly when shower humidity is at its maximum. The timeline: moisture from the shower rises and condenses in the first 10–15 minutes after the water stops. Without run-on, all that steam remains in the bathroom.

Mistake 3 — Installing a Ø100 mm fan on a Ø100 mm duct with a 90° bend A 90° bend on the duct reduces airflow by 15–20%. Two bends = minus 30–40%. A fan rated at 95 m³/h on paper delivers 55–65 m³/h in a real installed condition. Always go to the next diameter size up if you have more than one bend in the installation.

Mistake 4 — Not checking whether the building stack is functional Before installation, test with a piece of paper held near the ventilation grille (without the fan). If the paper is drawn toward the grille, the stack has natural draught. If it stays still or is pushed away, the stack is blocked or reversed — a fan installed there will not work correctly regardless of its power rating.

Mistake 5 — Mounting the fan near the door instead of above the shower Warm, humid air rises. A fan mounted high and above the shower/bath area extracts the most humid air. Mounted at mouth height, it extracts the cooler air near the floor and leaves steam at the ceiling.

Frequently asked questions

How much electricity does a bathroom fan use per month? A residential fan consumes 15–25W. At 2 hours of operation per day: 25W × 2h × 30 days = 1.5 kWh/month — less than 0.40 euros per month at current tariffs.

Can a bathroom fan be installed without an electrician? The mechanical installation (fixing to the wall, connecting to the duct) is straightforward and can be done by anyone with basic DIY experience. The electrical connection in a bathroom (wet zone) must be executed or verified by a qualified electrician under Romanian regulations.

Does the bathroom fan disturb neighbours? No, if the building ventilation stack is separate per apartment (standard in post-1990 blocks) and if the backdraft damper is functional. Noise transmission through the duct depends on fan quality — Casals models at 26–32 dB(A) are practically inaudible from a neighbouring apartment.

What if the bathroom has no exterior wall and the building stack doesn't work? Options include mechanical ventilation through ducts to an available exterior wall (via ceiling, technical corridor), or an inline fan on the ductwork reaching the exterior. ventilation.ro offers free consultancy for these atypical situations.

Why ventilation.ro and not general retailers

DIY chains and online marketplaces sell bathroom fans because they are listed in the catalogue — not because they can help you choose correctly. At ventilation.ro:

• Direct importer of Casals Spain — no intermediary pricing, guaranteed local stock
• Original technical documentation — manufacturer data sheets, real performance curves, CE declarations
• Free consultancy for correct sizing for your specific bathroom
• 24-month warranty on all Casals residential products
• Fast delivery from own stock

📞 +40 722 667 239 — tell us your bathroom area and we recommend the right model in 2 minutes 🌐 Residential fans — complete range

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