I am a U. S. Federal Empoyee that is stationed overseas, and I receive a non-taxable housing allowance for the place I am renting while overseas. However, I have a home in Virginia that is unoccupied and due to the homeowner rules cannot be used as rental property. Under these circumstances may I depreciate the house? Deduct all of the expences used to keep the house in good repair (water, electric and gas, insurance, security alarm etc)?

No, as you are paying for home expenses at only one place. For overseas, you are getting house allowance.