Most of these fires involve Churches and Public buildings. Install lights covering all sides of the building including the parking areas. Motion activated lighting, which is very inexpensive, should be placed near entrances. Don't advertise that a building is empty. Interior lights on timers give the illusion that the building is occupied.
Arsonists work mostly at night.
Buildings with a dark exterior provide many hiding places for arsonist. Alarm devices can be inexpensively wired through the telephone circuits to transmit an alarm to the Police or Fire Department. Check the cost of contracting with a security firm for response to alarms. Make sure that nothing blocks the view of the building. During the growing season, bushes and trees may need to be trimed frequently.