Kitchen exhaust fans are heavy and bulky, but they have to be moved in order to properly clean the fan and the ductwork underneath. If the fan is hinged as code requires, the cleaning crew can simply tilt the fan out of the way and then replace it exactly where it came from when they are done. If they have to lift it off, they will also have to put it down on your roof, and then maneuver it back into place when they are finished. That can nick up your roof and/or dent the base of the fan. They will also have to disconnect and re-connect electrical cords. Also, it creates risks of slips, falls, drops, and strains.
Your kitchen exhaust system is designed to pull grease vapor up and away from your cooking surface. Some of it will stick to the grease filters right above the stove. Some of it will stick to the ductwork. Some of it will stick to the fan blades. But some of it is going to get thrown into the air right above your roof, and some of what reaches your fan will eventually collect up and leak onto your roof. That’s rough on your roof, in addition to being a safety hazard for whoever might be walking around up there.
There are several good roof protection solutions out there. Several involve putting a gutter around the fan to collect the grease, in some cases with a pillow of sorts to absorb it.
If you need hinge(s) on your fans, or a rooftop grease problem, we can help, but however you get it done, it’s worth checking out.