Campervan rooflights and ventilation explained

Nobody gets excited about ventilation, and yet it is the difference between a van that stays dry and one that grows mould. Two people sleeping, a kettle, wet coats: a sealed van fills with moisture fast, and that moisture has to go somewhere.

This guide is the advice we give customers planning what goes in the roof. It covers why ventilation matters, how a rooflight differs from a powered fan, how to actually beat condensation, sizing and placement, and what the fit involves.

Two people sleeping in a van overnight breathe out a surprising amount of moisture. Add a kettle, cooking, wet coats and wet dogs, and the air inside a sealed van gets damp fast. That moisture condenses on the coldest surfaces, the windows, the metal, anywhere a thermal bridge reaches the cold outside.

Persistent condensation is not just unpleasant; left alone it works its way into the insulation and the metal, and mould follows. The fix is air exchange: damp inside air out, drier outside air in. That is the whole job of campervan ventilation, and it is why the roof of a good build always has something in it.

There are two things you can put in a van roof, and they do different jobs.

A rooflight is a domed skylight that lets daylight in and opens for natural ventilation. It usually has an integrated blind and flyscreen. It brightens the van and provides passive airflow, air moves through it when there is a breeze or a temperature difference. It does not force air anywhere; it is an opening.

A powered roof fan is an electric fan in the roof that actively moves air. The good ones run at a range of speeds, hold a set temperature on a thermostat, and reverse to either pull stale air out or push fresh air in. A powered fan is what actually shifts condensation and cooking smells, on demand, whether or not there is a breeze.

Think of them as a pair rather than a choice. Many good builds fit a rooflight toward one end of the van for light and passive air, and a powered fan toward the other for active extraction. If you only fit one powered item, make it the fan. If you want light as well, add a rooflight.

Ventilation is the main lever, but it works alongside the rest of the build:

• Air exchange. A powered fan in extract mode pulls damp air out. In intake mode it pushes fresh air in and slightly pressurises the van, which clears window condensation on a cold morning. This is the single most effective tool.
• A crack of airflow overnight. A rooflight cracked open, or a fan on its lowest speed, keeps a small constant air exchange going while you sleep. That is when most moisture is produced.
• Insulation. Good insulation reduces the cold surfaces that moisture condenses onto. Ventilation and insulation work together; neither alone is enough.
• Source control. A pan lid while cooking, drying wet kit outside where possible, all reduce the moisture you have to ventilate away.

A rooflight alone helps. A powered fan, used properly, is what actually keeps a van dry.

Size. The common campervan roof opening is 400 x 400mm, and both a standard rooflight and a powered fan are made to suit it. If you are replacing an existing rooflight of a different size, you may need an adapter frame to bridge the gap — do not assume a new unit drops straight into an old hole.

Roof thickness. Rooflights are designed for a range of roof thicknesses. A heavily insulated build with a thick false roof can fall outside the standard range and need spacer packing. Check the unit's stated thickness range against your actual roof build-up.

Placement. Put a powered fan where it earns its keep, over the kitchen to extract cooking moisture, or over the bed for sleeping airflow. If you are fitting both a rooflight and a fan, separate them along the van so air is drawn across the space rather than straight back out of the same spot.

A rooflight with no LED needs no wiring at all. A rooflight with an integrated LED needs a modest 12V feed for the light.

A powered fan is a 12V load on the leisure circuit. Airflow scales with fan speed, and so does current draw, a powered roof fan at top speed pulls in the region of 3 amps, but in normal use you run it on a low speed where the draw is small. Size it into your electrical system, but it is a far smaller steady load than a fridge.

• Cut-out. A new install means cutting an accurate 400 x 400mm hole. Replacing an existing unit means checking the old cut-out size first.
• Sealing. Bed the unit on butyl tape and seal the flange with polyurethane sealant. A roof leak ruins the interior beneath it — this is the step to get right.
• Roof thickness. Confirm your roof build-up is within the unit's stated range, or pack accordingly.
• Headlining. You will need to trim the interior cladding or headlining around the internal frame.
• Wiring. Only needed for a powered fan or an LED rooflight; a plain rooflight needs none.

If cutting a hole in your roof worries you, this is a fair job to pay an installer for.

We stock one powered fan and one rooflight, so you can cover both jobs:

• MaxxFan Deluxe — the powered fan, in 400, 350 or 280 Compact sizes. Ten speeds, reversible airflow, a thermostat, and a rain cover so it runs in the rain. The default powered roof vent for UK self-builds and the one to fit if you fit only one.
• MaxxFan Dome — the bathroom extractor. A small 6-inch exhaust fan for the shower, wardrobe or wet area. Pair with the Deluxe; not a replacement for it.
• SkyMaxx Rooflights — the rooflight, in 400×400 or LX 500×700 sizes, each with a standard version and a Plus version with an integrated LED. Fits 23-60mm roofs in the 400 size with no adapter, integrated blind and flyscreen.

A common build fits one of each: the MaxxFan Deluxe for active extraction, the SkyMaxx for light and a second vent, and the Dome over the bathroom if there is one.

• Product: MaxxFan Deluxe rooflight fan — 400, 350 or 280 Compact, Clear/Tint or Smoke lid
• Product: MaxxFan Dome bathroom extractor
• Product: SkyMaxx rooflights — 400×400 or LX 500×700
• Pillar: Campervan fridges explained