The day rate clause nobody reads

Most commercial property policies carry an unoccupancy condition. Leave a building empty for a set period, commonly thirty or forty-five consecutive days, and cover contracts to a much narrower set of perils: usually fire, lightning, explosion and aircraft, and nothing else.

The conditions come with chores

Alongside the narrower cover, the condition usually imposes duties: drain down the water system, isolate services except those needed for alarms, inspect at set intervals and keep a written record, secure letterboxes. Miss the inspections and the insurer has grounds to decline even the perils that remain.

None of this is unreasonable. It is simply invisible until a tenant leaves and nobody tells the broker, which is why a change of occupancy should be a phone call on the day it happens rather than a note for the renewal.