The amount of space you have at the ceiling level will determine whether you can convert a hanging ceiling fan to a flush-mount. A ceiling fan needs to be installed eight to nine feet from the ground. This keeps the fan high enough to prevent accidents from the blades hitting a standing person, but it is low enough for the fan to effectively move air at the level where people are walking. If you have a lofted ceiling, a flush-mounted fan will not cool the space as effectively as a hanging fan because it will be too high. Flush-mounted fan also cannot be installed on sloping or angled ceilings because the fan blades must hang parallel to the floor for proper operation.
The mounting box might need to be changed if you convert from a hanging ceiling fan to a flush-mounted fan. Some downrod fans use a surface-mounted fan box. This box secures the fan to the ceiling frame and protects the wiring connection from the house to the fan. To convert to a flush mount, a hole in the ceiling needs to be cut to install the mounting box inside the ceiling with the open base of the box at level with the ceiling. This mounting box is where you screw the fan mounting bracket to hold the fan against the ceiling.
The air flow for flush mounted fans is less than hanging fans. This is because there is less air above a flush-mounted fan for the appliance to force to the ground. Hanging fans can more more air because there is more space between the ceiling and the fan blades. If you want the maximum amount of air flow, you might want to retain a hanging fan instead of converting it.
Safety is an issue with fans. If you installed a hanging fan in a room with a ceiling lower than eight feet, you must convert it to a flush-mounted fan. A ceiling fan that hangs too low from the ceiling can hit a tall person walking in the room, or the arm of someone who raises a hand near the fan. Hanging fans with light fixtures installed too low compound the problem by adding the lights hanging from the middle of the fan as an additional obstacle.