RV OWNER’S FIELD GUIDE · APPLIANCES
Roof Vent & Fan Install Guide
A roof vent fan is one of the highest-value van build upgrades — and one of the easiest installs to turn into a future leak if the sealing isn’t done right.
Where It Sits in the Roof Structure
The opening needs to land between roof ribs/framing, not through one, and the flange needs full contact with the roof surface all the way around — a corner that’s not fully bedded in sealant is exactly where water finds its way in months later, often nowhere near where the leak eventually shows up inside.
Sealant Choice Matters
Self-leveling lap sealant is the standard for horizontal roof penetrations — it’s designed to stay flexible through roof expansion/contraction. Standard caulk or silicone will eventually crack under that movement even if it looks fine on install day. This is a case where the cheaper tube of sealant is a false savings.
Wiring It In
Most 12V fans draw enough that a dedicated fused circuit back to the panel is the right approach rather than tapping an existing light circuit — especially on multi-speed or thermostatically controlled fans that can pull more current on startup than their running spec suggests.