If your bathroom has no window, you need mechanical ventilation. This isn’t a recommendation — it’s a legal obligation and, above all, a health matter. An interior bathroom without ventilation accumulates relative humidity above 80% after each shower, the perfect breeding ground for mould, dust mites, and that stale smell we’ve all experienced. At Bathscape we renovate many interior bathrooms in Valencia — especially in city-centre, Ensanche, and Ruzafa flats — and ventilation is always one of the first decisions of the project.
What the Regulations Say
The CTE (Technical Building Code), in its Basic Document HS-3 on indoor air quality, establishes clear requirements for bathroom ventilation:
- Minimum extraction rate: 15 L/s per room (equivalent to 54 m3/h) for bathrooms.
- Air intake: Replacement air must enter from dry rooms (bedrooms, living room) and be extracted from wet rooms (bathrooms, kitchen).
- Continuous operation: Ventilation must operate permanently, not only when the bathroom is in use.
This last point surprises many people. The regulations don’t say “install an extractor that turns on with the light.” They state that ventilation must be continuous to guarantee indoor air quality. In practice, high-capacity intermittent ventilation meeting equivalent air changes is accepted, but the spirit of the regulation is clear: bathroom air must always be moving.
According to data from IDAE, Spanish buildings constructed before 2006 (when the CTE came into force) rarely meet these ventilation requirements. If your flat predates that year and your bathroom has no window, it’s almost certain the current ventilation is insufficient.
Option 1: Axial Extractor (the basic solution)
The axial extractor is the classic wall or ceiling fan that expels stale air through a duct to the building exterior. It’s the simplest and most affordable solution.
How it works: An electric motor spins blades that propel air in one direction (axial = along the axis). Air exits the bathroom and is channelled through a duct to the facade, light well, or shunt (the building’s communal duct).
Capacity: Domestic models range from 80 to 200 m3/h. For a standard 5-8 m2 bathroom, 100-120 m3/h is sufficient.
Noise: Here’s the drawback. Axial extractors generate between 30 and 45 dB(A). Budget models can reach 50 dB(A), which is a noticeable nuisance, especially at night. Imagine being asleep and your partner gets up for the bathroom at 3 am: if the extractor sounds like a jet taking off, fun is guaranteed.
Price: EUR 30-150 (unit) + EUR 100-200 (installation if duct exists). If a new duct is needed, cost rises to EUR 300-600 total.
Recommended models: Soler & Palau Silent series (33-38 dB), S&P TD Silent (for duct), Vortice Punto M.
Axial Extractor Variants
- With timer: Turns on with the light and continues running 5-15 minutes after switching off. Eliminates residual post-shower humidity.
- With humidity sensor (hygrostat): Activates automatically when humidity exceeds a threshold (typically 70-75%). More efficient than the timer because it only operates when needed.
- With presence detector: Turns on when it detects movement. Combined with a timer, it’s a good solution for guest bathrooms.
Option 2: Centrifugal Extractor (quieter)
The centrifugal extractor uses an impeller that propels air perpendicular to the intake axis. This geometry is more aerodynamically efficient and, above all, quieter.
Advantages over axial:
- Lower noise at equal airflow (25-35 dB in premium models)
- Higher static pressure: can push air through longer ducts and more bends
- Better performance with shared ducts (building shunts)
Disadvantages: Larger size, higher price.
Price: EUR 80-300 (unit) + EUR 100-200 (installation).
At Bathscape we recommend centrifugal when the duct is longer than 3 metres or has more than one bend, or when the master bedroom is adjacent to the bathroom and noise is critical.
Option 3: Dual-Flow HRV (the most efficient)
Dual-flow HRV (Heat Recovery Ventilation) is a centralised system that extracts stale bathroom air while simultaneously introducing fresh outdoor air, passing both flows through a heat exchanger.
How it works: The air leaving the bathroom (warm and humid) passes through an exchanger where it transfers up to 90% of its heat to the incoming air (fresh from outside). The result: continuous ventilation with minimal energy loss.
Why it matters: In a windowless bathroom with a conventional extractor, every cubic metre of extracted air is replaced with untreated outdoor air. In winter, that means cold air entering through door and window gaps, cooling the home and increasing heating bills. Dual-flow HRV prevents this problem.
Capacity: Domestic units handle 150-400 m3/h, sufficient for the entire home (bathrooms + kitchen + living areas).
Noise: 20-30 dB(A) at the unit, inaudible in the bathroom if correctly installed (in a hallway false ceiling or storage room).
Price: EUR 1,500-4,000 (unit) + EUR 1,000-2,500 (ductwork installation). It’s a significant investment, but covers the entire home, not just the bathroom.
Dual-flow HRV is the technically superior option. At Bathscape we recommend it when a full home renovation is underway (not just the bathroom) because it requires a duct network affecting the entire property. If only the bathroom is being renovated, the cost is hard to justify.
Option 4: Smart Extractors (the intelligent option)
Smart extractors take the basic concept of the axial or centrifugal extractor to the next level with sensors and connectivity:
Humidity + temperature sensor: The extractor continuously measures bathroom conditions and proportionally adjusts fan speed. It’s not on/off — it’s continuous regulation. When humidity drops below threshold, it reduces to minimum speed, maintaining silent background ventilation.
CO2 sensor: The most advanced models measure air quality (CO2 as indicator) and ventilate more when air quality degrades. Useful in large or shared bathrooms.
WiFi connectivity: App control, time scheduling, usage and consumption statistics. Integration with smart home ecosystems (Alexa, Google Home, HomeKit).
Learning: Some models learn the bathroom’s usage patterns (shower times, high-humidity days) and anticipate ventilation so the bathroom is ready before you enter.
Price: EUR 150-400 (smart unit) + EUR 100-200 (installation).
Notable models: Airflow iCon, Vent-Axia Svara, Soler & Palau Silent Dual.
Our view at Bathscape: if you already have home automation, a smart extractor is the natural evolution. If not, a centrifugal with hygrostat does the job perfectly and costs half as much.
Noise Levels: The Table You Need
Noise is the factor generating the most complaints about bathroom extractors. Here’s the reference:
| Level (dB) | Equivalent | Acceptability |
|---|---|---|
| < 25 dB | Whisper | Inaudible in practice |
| 25-30 dB | Gentle breeze | Excellent, not bothersome |
| 30-35 dB | Refrigerator | Acceptable by day, slightly bothersome at night |
| 35-40 dB | Quiet conversation | Bothersome if bedroom is adjacent |
| > 40 dB | Moderate rain | Unacceptable for night-time use |
Golden rule: if your bedroom shares a wall with the bathroom, don’t install anything above 30 dB(A).
Ductwork: The Forgotten Element
The world’s best extractor is useless if the duct is poorly sized, has too many bends, or discharges in an unsuitable location.
Diameter: Minimum 100 mm for extractors up to 150 m3/h. 120-150 mm for higher airflows. A duct that’s too narrow generates aerodynamic noise and reduces effective airflow.
Material: Rigid PVC or galvanised sheet metal pipe (preferable). Avoid corrugated flexible aluminium tubing except for short runs (< 1 m): it generates more pressure loss and accumulates grease and dust.
Bends: Each 90-degree bend equals 1-1.5 m of straight duct in terms of pressure loss. Minimise bends and use wide-radius elbows.
Discharge: Always to the building exterior (facade or roof), never into a false ceiling, enclosed box, or the inside of a cupboard. The discharge must have a non-return grille to prevent air (and potentially neighbours’ odours) from coming back in.
In Valencia flats, the duct typically connects to the building’s shunt (vertical communal duct). If the shunt is blocked or has insufficient cross-section, the extractor won’t work well no matter how good it is. Checking the shunt’s condition before the renovation is one of our technical checklist items at Bathscape.
Correct Sizing
To comply with CTE DB-HS3 in a bathroom, the minimum extraction rate is 15 L/s = 54 m3/h. But this is the regulatory minimum. In practice, we recommend:
- Small bathroom (< 5 m2): 80-100 m3/h
- Medium bathroom (5-8 m2): 100-150 m3/h
- Large bathroom (> 8 m2): 150-200 m3/h
- Bathroom with bathtub and shower: Add 20-30% to the base airflow (more evaporation surface)
Complete air renewal in the bathroom should occur 5 to 8 times per hour during active use (showering) and 1-2 times per hour at rest. A bathroom of 5 m2 x 2.5 m height = 12.5 m3. For 6 renewals/hour, you need 75 m3/h airflow.
Air Intake: The Other Side of the Equation
A classic error we see again and again: a powerful extractor is installed but the air intake into the bathroom is forgotten. If the bathroom is closed and no air enters, the extractor works against a vacuum and moves nothing. It’s like trying to drink from a bottle with the cap on.
Intake solutions:
Door grille: A ventilation grille in the bottom of the bathroom door (free opening of 70-80 cm2). The simplest and most effective. Aesthetically discreet if chosen in the same colour as the door.
Under-door gap: Leave 15-20 mm between the door and floor. Less elegant but equally functional.
Transfer duct: In high-end bathrooms, a transfer duct from the hallway to the bathroom with an acoustic attenuator. Air passes through but noise doesn’t. This is what we do in smart-tech designs at Bathscape.
Common Errors We See
Extractor connected to the light: The extractor turns off when you switch off the light, precisely when humidity is highest (post-shower). Minimum: 15-minute timer. Ideal: independent hygrostat.
Duct terminating in false ceiling: Humid air accumulates in the false ceiling, causing dampness and mould. The duct must always reach the exterior. More on technical errors in renovations.
Overpowered extractor: An oversized extractor generates more noise than necessary and can cause depression problems (doors that don’t open easily, draughts). A correctly sized extractor at medium speed is better than a large one at minimum speed.
Not cleaning the extractor: Filters and blades accumulate dust and grease. Recommended cleaning: every 3-6 months. A dirty extractor loses up to 30% of effective airflow.
Frequently Asked Questions
My bathroom has a shunt but it doesn’t seem to draw. What should I do?
First, verify with a simple test: hold a sheet of paper near the shunt grille. If it sticks, there’s natural draught. If not, the shunt may be blocked or have insufficient cross-section. A camera inspection (EUR 100-200) identifies the problem. If blocked, it can be cleaned. If the cross-section is insufficient, the solution is a mechanical extractor that forces the air.
Can an extractor be installed in a bathroom without a duct to the outside?
In theory, no bathroom should lack access to exterior ventilation (regulations require it). In practice, they exist. The solution is to create a new duct: through the exterior wall if the bathroom has a wall to the facade, or through the hallway false ceiling to reach a shunt or facade. Cost varies between EUR 300 and 1,000 depending on distance. In renovations in Valencia, we always find a viable solution.
Does an extractor with a humidity sensor replace the CTE’s permanent ventilation requirement?
Strictly, no. The CTE requires continuous ventilation. A hygrostat that only activates with high humidity doesn’t literally comply with the regulation. However, many smart extractors have a “trickle” mode that maintains a minimum continuous airflow (10-20 m3/h) and increases power when humidity is detected. This does comply with the regulatory spirit.
Your bathroom has no window and needs to breathe? At Bathscape we design integrated ventilation solutions within the renovation — invisible and efficient. Configure your project and let the air flow.