Fitting a roof vent fan in a VW pop-top campervan

The Problem

You want to fit a powered roof vent fan to deal with extreme summer heat in a VW pop-top campervan, but you are unsure whether the reinforced pop-top roof section has enough clearance, how to cut and mount the fan safely, how to seal the new roof penetration against water, and how to wire the fan in.

Solution

1. Identify which pop-top you have first. VW pop-top roofs are fitted by several manufacturers (Reimo, Pendle, SCA, Austops and others) across the T4, T5, T6 and T6.1 generations, and the flat reinforced area, panel thickness and internal framing differ between them. Confirm your generation and roof brand (check any badge, the conversion paperwork, or measure the flat panel yourself) before assuming the dimensions below apply. (confirm this applies to your VW generation and pop-top brand)
2. Identify the flat reinforced section of the pop-top roof between the pull-down handles and measure it against the fan's required aperture to confirm fit.
   • The 355mm Nomadic AirPlus fits this area on the roof this guide was written for; the 400mm version does not. On a different generation or pop-top brand the flat section may be smaller or shaped differently, so measure before ordering.
3. Drill a pilot hole in the intended cut zone to check actual roof thickness before buying mounting hardware.
4. Cut back the foam-backed faux-suede headlining around the cut zone so the jigsaw blade cannot snag it during the roof cut.
5. Mark the cutting outline on the roof surface using a white paint pen.
6. Cut the aperture through the pop-top roof panel using a Bosch carbon fibre jigsaw blade.
   • The roof in this area may be thicker than expected, which is beneficial for structural integrity.
7. Seal the cut edge and the fan flange — do not skip this, as any roof penetration will leak otherwise. Before mounting, deburr and clean the cut edge, then prime/seal the exposed core of the cut aperture (an exposed foam, GRP or composite core will wick water if left bare) so moisture cannot track into the panel. Bed the fan's mounting flange onto a continuous bead of a non-setting, UV-stable RV roof sealant — a butyl tape gasket plus an overband of Sikaflex 512 Caravan, Dekalin or equivalent on the outer flange is the typical approach. Run the sealant in an unbroken ring with no gaps at the screw points, then leave it to cure before testing. After fitting, water-test with a hose (or wait for heavy rain) and check inside for any ingress. (verify the exact sealant grade is compatible with your pop-top roof material — some GRP and ABS roofs require a specific primer; confirm with the pop-top manufacturer or your dealer)
8. Cut an 18mm plywood backing ring to surround the aperture on the inside, bringing the total mounting depth to approximately 28mm and meeting the fan's minimum 27mm requirement.
9. Cover the plywood ring with foam-backed faux-suede lining, choosing a slightly different shade of grey rather than attempting a near-match.
   • A close-but-wrong match looks worse than a deliberate contrast.
10. Fit the Nomadic AirPlus into the opening using screws sized for the combined roof and ply thickness, measuring first and sourcing the correct lengths before fitting.
11. Wire the fan to a fused 12V supply. The Nomadic AirPlus is a 12V DC fan, so run it from the leisure battery circuit, not the starter battery. Route the two-core cable from the fan down through the pop-top roof and along the pop-top bellows/concertina into the body — feed it where the existing pop-top wiring (if any) or the canvas seam runs so it is protected when the roof is raised and lowered, and leave a service loop so the cable is not pulled taut at full extension. Use cable rated for the fan's current draw — for a low-draw vent fan 1.0–1.5mm² (roughly 16–18 AWG) is normally ample over a short run, but size it to the manufacturer's stated current and your cable length, stepping up the gauge for longer runs to limit voltage drop. Protect the circuit with an in-line fuse fitted at the supply (leisure battery / fuse-box) end, sized just above the fan's rated draw — typically a 3–5A fuse for a fan of this type. Connect to a switched feed from the leisure-battery distribution/fuse box rather than splicing into vehicle wiring, and fit a grommet or proper gland anywhere the cable passes through a panel to prevent chafing. (verify the fan's rated current, recommended fuse rating and recommended cable gauge against the Nomadic AirPlus instructions before wiring)
12. Check clearance between the bed surface and the underside of the fan before finalising the installation.

• On a long-wheelbase van with an 18-inch bed extension, clearance was 35mm, reducing to 20mm at the manual lift knob, with roughly 40% of the fan covered by the sliding bed panel — acceptable as the fan is primarily used while sleeping with the roof raised.