Dometic sells its Midi and Mini Heki Style Rooflights either with forced ventilation or without forced ventilation. Let's break down what the difference is -
What “without forced ventilation” actually means
A Dometic rooflight without forced ventilation:
- Has no fixed ventilation slots in the frame
- Seals fully when closed
- Does not provide continuous airflow
- Relies entirely on you opening the rooflight for ventilation
This is the opposite of “forced ventilation,” where the rooflight includes mandatory airflow vents that cannot be closed.
Why Dometic makes both versions:
✔️ Forced ventilation models
Required by some vehicle regulations (especially older caravan/motorhome standards). They allow a minimum amount of airflow at all times for safety.
✔️ Without forced ventilation models
Chosen when:
- The vehicle already has enough ventilation elsewhere
- You want better insulation
- You want less draught
- You want a fully sealed rooflight (e.g., for winter use or noise reduction)
Below is the UK + EU compliant explanation, written specifically for motorhomes, campervans and caravans:
1. What “forced ventilation” means in regulation
In motorhome and caravan construction, forced ventilation refers to permanent, non‑closable openings built into windows, rooflights or vents that allow a minimum amount of fresh air to enter the vehicle at all times, even when everything is closed.
These openings are usually:
- Small slots in the frame
- Fixed grills
- Gaps integrated into rooflights (e.g., some Heki models)
They cannot be shut, because they are required for safety.
2. The actual rules (UK + EU)
Motorhomes and caravans must comply with EN 721 (European Standard for Ventilation of Leisure Accommodation Vehicles). This is the regulation that dictates ventilation requirements.
EN 721 requires:
- Permanent ventilation must be provided
- It must meet a minimum free‑air area (measured in cm²)
- It must be non‑closable
- It must be positioned to ensure safe dispersal of gas and fumes
This applies to:
- LPG appliances
- Gas fridges
- Heaters
- Cookers
- Any vehicle with a gas installation
If your vehicle has gas, you must have forced ventilation somewhere in the structure.
3. Does the ventilation have to be in the rooflight?
No — and this is where confusion comes from.
EN 721 says you must have permanent ventilation, but it does not say it must be in the rooflight.
Permanent ventilation can be provided by:
- Rooflights with forced ventilation
- Windows with forced ventilation
- Floor vents
- Dedicated fixed vents in the bodywork
This is why Dometic sells:
- Midi & Mini Heki Style WITH forced ventilation
- Midi & Mini Heki Style WITHOUT forced ventilation
If your vehicle already meets EN 721 through other vents, you can legally use a non‑ventilated rooflight.
4. Why many motorhomes still use forced‑vent rooflights
Manufacturers often choose rooflights with forced ventilation because:
- It guarantees compliance
- It avoids relying on floor vents that can be blocked
- It ensures airflow even when blinds are closed
- It reduces risk of gas buildup
But for van conversions, many installers prefer non‑ventilated rooflights because:
- They seal better
- They reduce drafts
- They improve insulation
- They reduce noise
- They prevent heat loss in winter
As long as the vehicle has other permanent vents, it remains compliant.
5. How to know if YOUR motorhome needs forced ventilation
You need forced ventilation if:
- You have LPG appliances
- You have a gas fridge
- You have a gas hob or oven
- You have a gas heater
You do not need forced ventilation in the rooflight if:
- Your vehicle already has floor vents
- Your windows have built‑in ventilation slots
- Your conversion includes fixed body vents
Summary
- Forced ventilation = permanent, non‑closable airflow
- Required under EN 721 for any vehicle with gas
- It does not have to be in the rooflight
- You can use a non‑ventilated rooflight if your vehicle already meets the ventilation requirement
- Dometic offers both versions to suit different vehicle designs