A roof fan only moves air properly if fresh air has a way into the van. That matters when choosing between a passive vent and a powered fan, and when deciding where to cut the roof.

Two people sleeping in a small metal box produce a surprising amount of moisture just by breathing. Add wet coats, boiling a kettle, cooking dinner and perhaps drying a towel, and that moisture has to go somewhere. In summer you have the opposite problem as well: the sun heats the bodywork and the inside of the van can become unbearably hot.

A roof vent helps with both, but there is quite a difference between simply having a hole in the roof that lets warm air rise out and fitting a powered fan that can actively move air through the van.

The important bit is not really the fan itself. Good ventilation needs a route for air to come in and a route for air to go out.

Passive roof vent or powered fan?

A passive roof vent is the simple option. Open it and warm air can rise out naturally. Some models, including the Fiamma Vent 40 discussed below, are specifically designed to provide permanent background ventilation even when closed; an ordinary unpowered rooflight may only ventilate when it is open. There is no fan motor and therefore no fan electrical consumption.

For a simple weekend campervan, that may be all you need, especially if you can also crack a window or open another vent on the opposite side of the van.

A powered roof fan gives you much more control. It can actively pull warm, moist air out, and reversible models can also draw outside air in. That becomes particularly useful when cooking, trying to cool a hot van quickly or sleeping with everything else largely closed.

If summer heat is your main concern, our tips for keeping cool in your campervan cover the other things that make a surprisingly big difference too.

Extraction or blowing air in?

There is no single setting that is right all the time.

If you are cooking, extracting makes obvious sense because you are trying to remove hot, damp air near its source. On a hot day, extraction also works well if you can open a shaded window or another rooflight elsewhere in the van: the fan pushes hot air out and replacement air is pulled in through that other opening.

At night, some owners prefer the fan blowing cooler outside air directly towards the sleeping area. Others find extraction quieter and more comfortable. Fan position makes a big difference.

What matters is that the moving air has somewhere to go. A powerful fan trying to extract from a completely sealed van cannot create a useful through-draught.

Where should you put a roof fan?

If I were planning a conversion from scratch, I would think about the airflow before reaching for the jigsaw.

Over or close to the cooking area is a sensible place for an extractor because steam and hot air are removed before they spread through the van. You can then use a window, cab vent or another rooflight further away as the air inlet.

Putting the fan over the bed can also work well if overnight cooling is the priority, particularly with a reversible model. The trade-off is that motor noise is then directly above where you sleep.

There is also a very practical consideration: the roof itself. Panel vans have ribs, roof strengthening sections, solar panels, roof rails, aerials and sometimes wiring hidden behind the headlining. The ideal airflow position still has to be somewhere you can physically fit the vent properly.

Before cutting anything, check the exact aperture required by the model you are buying. A 400 x 400mm European roof fan and a 14 x 14in model are close in size, but they are not the same thing.

Fitting one is mostly about the roof, not the fan

The electrical side of a 12V roof fan is usually fairly modest. The part that deserves the most care is cutting a large hole in a perfectly good van roof and then making sure it never leaks.

On a ribbed panel-van roof, a shaped adapter can give the vent a flat surface to sit on. The cut edge also needs protecting before the vent is fitted, because leaving bare steel hidden under a flange is asking for rust later on.

The vent then needs to be bedded and sealed using materials suitable for the roof and the vent manufacturer’s fitting method. This is one of those jobs where taking your time with the measuring and sealing is far more important than doing it quickly.

A powered fan also needs a suitable 12V feed and fuse. Our campervan electrics guide is useful background if you are planning the electrical system at the same time.

What difference does a roof fan make to condensation?

Ventilation will not magically stop every cold window misting up, but it tackles the main problem: moist air trapped inside the van.

Cooking is an obvious source. A boiling pan or kettle puts water vapour straight into the living space, so getting that air outside rather than allowing it to settle on cold glass and metal makes sense. See our cooking in a campervan guide for the broader cooking options.

Sleeping matters too. Even with no cooking at all, people breathe moisture into the van through the night. Leaving some ventilation open and allowing air to move is normally much more effective than trying to seal the van up because it is cold outside.

That does not mean running a fan flat out all night. A low setting with a second opening elsewhere in the van may be all that is needed.

Noise and electricity use

One advantage of a passive vent is obvious: it is silent and uses no electricity.

A powered roof fan can run for many hours, so its electrical use is worth counting properly rather than dismissing as insignificant. Consumption varies with the fan and speed setting, and overnight use can add a noticeable amount to your daily total.

Noise matters too when the fan is directly above where you sleep. A multi-speed fan is useful because you can run it gently overnight rather than choosing between full power and off. If you spend a lot of time off-grid, include the fan in your normal daily watt-hour calculation. The same approach we use in our solar-panel guide works here too.

Two current roof-vent options worth comparing

Some of the product links in this article are Amazon affiliate links. If you buy through one of them I may earn a small commission, at no extra cost to you.

There is no point pretending these two products do the same job. One is an active powered ventilation system; the other is a much simpler passive roof vent.

Maxxair MaxxFan Deluxe 7500Ki40 – powered ventilation with rain protection

The Maxxair MaxxFan Deluxe 7500Ki40 is the sort of fan I would look at where active ventilation is important.

This European 400 x 400mm version has a 12V ten-speed reversible fan, so it can either extract air or draw it into the van. Its built-in rain shield is particularly useful in UK weather because you can keep ventilating without having to close the roof vent every time it starts raining.

It also has thermostat control, a remote and an insect screen. The downside is obvious: it costs considerably more than a simple vent and needs both a suitable roof opening and a 12V supply.

Best fit: campervans used regularly for cooking, sleeping and touring where controllable ventilation in wet as well as hot weather is worth paying for.

Fiamma Vent 40 – simple passive ventilation

The Fiamma Vent 40 takes the opposite approach. It is a 40 x 40cm roof vent with permanent ventilation, a handwheel opening system and a mosquito net, but no powered fan.

For a basic campervan that can be a virtue rather than a limitation. It uses no electricity, makes no fan noise and gives warm air somewhere to escape. Open a window or another vent elsewhere and you can still create useful natural airflow through the vehicle.

Best fit: simpler conversions, occasional-use vans or anyone who wants permanent background ventilation without adding another electrical appliance.

Do you actually need a powered roof fan?

Not every campervan does.

If you mainly use campsites, already have a decent rooflight and windows that can be securely left on a vent setting, a passive setup may work perfectly well. It is simple, silent and cheap to run because there is nothing to run.

A powered fan starts earning its space when you regularly cook inside, sleep in the van for several nights at a time or tour in hot weather. Being able to actively shift air can be much more useful than simply opening a rooflight and hoping for a breeze. If wet-weather ventilation matters, choose a model specifically designed to operate in the rain, such as the covered MaxxFan Deluxe below; that is not a feature of every powered roof fan.

I would also think twice before replacing a perfectly good existing rooflight just because powered fans are fashionable. If the ventilation you already have works, there may be better places to spend the money.

Roof fan or air conditioning?

They are completely different things.

A roof fan moves air. It can remove the layer of hot air trapped inside the van and make you feel much more comfortable by creating a breeze, but it cannot make the incoming air colder than the air outside.

Proper air conditioning actively cools the air, but it needs far more electrical power. For many campervans, improving shade and ventilation is the much simpler first step before considering air conditioning.

Our conclusion

For a small or occasional-use campervan, I would start by making sure there is a proper route for natural airflow. A good passive roof vent may be all that is required.

For a van that is used regularly, especially for cooking and overnight touring, a powered reversible roof fan is much easier to justify. It can pull damp air out or bring outside air in, and a covered model such as the MaxxFan Deluxe can continue ventilating in wet weather.

Whichever type you choose, plan the airflow before you choose the hole in the roof. Where the fresh air comes in matters just as much as where the fan sends the old air out.