However, one big mistake people make, and this can lead to damage in high heat, is to have a vacant home sealed up very tight with little to no air flow. If there is any source of moisture in these situations the home can become a breeding ground for mold and mildew. These mold and mildew claims are not covered by vacant home insurance or for that matter most homeowners insurance policies in most States.
Whenever possible a dehumidifier should be running in the basement at all times. The only way this is possible is for the dehumidifier to empty into a drain or if someone is entering the home at least once every 48 hours to empty the unit.
If this is not possible the house should not be sealed up ultra tight. The good news is, even if all windows are shut most (especially older) homes have at least some air flow on all levels of the house.