If you have a roof fan or vent in your campervan, you need a way to keep it open in the rain without water pouring in. The UK's unpredictable weather means you cannot rely on the forecast — a good vent cover lets you run your fan 24/7 regardless of the weather.
Our Recommendation
If you have a MaxxFan: Buy the Maxxair vent cover (£50). It is designed for the fan, minimises airflow loss, and installs in 2 minutes.
If you have a standard roof vent without a fan: The Fiamma universal cover (£35) is a good choice. It provides rain protection for a passive vent and works with most 350x350mm openings.
If you are on a tight budget: Make a DIY polycarbonate cover (£20). It works well but is not as refined or quiet as the branded options.
If you are buying a new fan: Consider the Fiamma Turbo Plus (£220) for an all-in-one solution with permanent rain protection. The lower airflow is a trade-off, but the convenience of never closing the vent is real in UK weather.
Why You Need a Vent Cover
A standard roof fan (even one with a rain sensor) will close automatically when it detects rain. This means:
- You lose ventilation on stuffy, rainy nights
- Condensation builds up faster with the fan closed
- The auto-close feature is good for preventing water ingress but bad for air quality
A vent cover allows the fan to run at any angle, in any weather, without water entering.
Types of Vent Cover
1. Maxxair Vent Cover (Premium)
Maxxair makes a purpose-designed vent cover for their own fans. It clips onto the fan housing and creates a rain shield.
Model: Maxxair MA00-03701 (for MaxxFan 4500K and 5100K)
Price: £40-60
How it works: The cover is a clear acrylic dome that sits 30mm above the fan housing. Air flows through side vents on the cover while the top deflects rain.
Pros:
- Designed specifically for MaxxFan
- Clear acrylic — does not block light
- Easy installation (clips on, no tools)
- Allows fan to run at full speed in heavy rain
Cons:
- Only fits MaxxFans
- Adds 40mm to roof height
- Acrylic can yellow after 3-4 years
2. Fiamma Vent Cover (Universal)
Fiamma produces universal vent covers that fit most 350x350mm roof vents (fan or passive).
Models:
- Fiamma Turbo Vent Cover: £30-45
- Fiamma Standard Vent Cover: £25-35
How it works: A white plastic cowl that mounts above the vent opening. It has a lower profile than the Maxxair cover.
Pros:
- Universal — fits most 350x350 vents
- Lower profile (adds 25mm to roof height)
- White colour blends with most van roofs
- Simple screw-on installation
Cons:
- Restricts airflow slightly (side vents are smaller)
- Plastic can become brittle in UV after 4-5 years
- Not designed for fans — works best with passive vents
3. Fiamma Turbo Plus (Active Vent + Cover)
The Fiamma Turbo Plus is a combination unit: a 12v fan with a built-in vent cover. The fan sits under a permanent rain cover that never closes.
Price: £180-250
Pros:
- Permanent rain shield
- Fan included (no separate purchase)
- Lower profile than MaxxFan + cover
- 3-speed fan
Cons:
- Less airflow than MaxxFan (550 vs 900 CFM)
- No thermostat or rain sensor
- Louder than MaxxFan on all speeds
4. DIY Vent Cover (Budget)
A simple DIY solution using clear corrugated polycarbonate sheet (like the roofing material from B&Q).
Materials:
- 500x500mm polycarbonate sheet (£8-12)
- 4x aluminium angle brackets (£4)
- Sikaflex (£8)
Assembly:
- Cut the polycarbonate to 400x400mm
- Attach angle brackets to each corner
- Screw brackets to the roof (mounting onto existing fan screw holes)
- The sheet sits 30mm above the fan, held by the brackets
Total cost: £15-25
Pros: Cheap, effective, fully custom. Cons: Does not look as neat, may not be as aerodynamic, could be noisy at speed.
Comparison Table
| Cover | Price | Fits | Airflow Impact | Profile | Installation |
|---|---|---|---|---|---|
| Maxxair cover | £50 | MaxxFan only | 5% reduction | +40mm | Clip-on |
| Fiamma Turbo cover | £35 | Universal 350mm | 15% reduction | +25mm | Screw-on |
| Fiamma Turbo Plus | £220 | Self-contained | 550 CFM (built-in) | +60mm | Full install |
| DIY polycarbonate | £20 | Any fan | 10% reduction | +30mm | DIY |
Airflow Impact
A vent cover always reduces airflow. Tests with a MaxxFan 5100K:
| Condition | Airflow (CFM) | Reduction |
|---|---|---|
| No cover, fan open | 900 CFM | -- |
| Maxxair cover, fan open | 855 CFM | 5% |
| Fiamma cover, fan open | 765 CFM | 15% |
| DIY cover, fan open | 810 CFM | 10% |
The reduction is minor for the Maxxair cover. The Fiamma cover's smaller side vents create more restriction.
Wind Noise
At motorway speeds (70mph), vent covers create wind noise:
- Maxxair cover: Moderate whooshing sound (about 55 dB)
- Fiamma cover: Lower pitched hum (about 50 dB) — better aerodynamic profile
- DIY cover: Variable — sharp edges create whistle at 50+ mph
UK Weather Reality
In UK conditions, a vent cover is worth having for 8-10 months of the year. From September to May, you will frequently want the fan running while it is raining. Without a cover, you either close the fan (no ventilation) or let rain in.
Regional differences:
- Scotland and NW England: Highest rainfall — vent cover essential
- SE England: Less rain but unpredictable — still worth having
- Coastal areas: Salt spray affects metal fan parts — a cover protects from salt
