IP Ratings Outdoors
An IP rating has two digits. The first is dust, on a scale to 6, where 6 means fully sealed. The second is water, where 5 means it withstands jets from any direction. IP65 is the practical minimum for a fitting under an open structure.
Reading the two digits
The first digit runs to 6 and describes solids. Six is complete protection against dust, which outdoors means pollen, grit and everything a dry wind carries into a motor housing.
The second runs to 9 and describes water. Four is splashing. Five is jets from any direction. Six is powerful jets. Under a roof that is open at the sides, rain arrives sideways in wind, which is why five rather than four is the number that matters.
What happens without it
An indoor fan hung under a pergola does not fail at the blades. It fails at the motor, where damp gets into the windings and bearings, and it usually fails in the second season rather than the first - long enough that the cause is not obvious.
Plug-in against hard-wired
A hard-wired fitting needs an electrician and an outdoor circuit. A plug-in one needs an outdoor socket, which most covered patios already have. For a structure that might be repositioned, plug-in is the more forgiving choice.
The fan shown here is IP65 and plugs in, with two downrods for different ceiling heights.
Questions
What does IP65 mean?
Fully sealed against dust, and protected against water jets from any direction.
Can an indoor fan be used outdoors?
It is not built for it. Damp reaches the motor windings and bearings, and the failure usually comes in the second season.
Is IP44 enough under a pergola?
IP44 covers splashing. Under an open structure rain arrives sideways in wind, which is what the higher water rating covers.