Greg: See https://www.healthcare.gov/quick-guide/eligibility/ which states
"U.S. citizens living outside the U.S.
U.S. citizens living in a foreign country for at least 330 days of a 12-month period are not required to get health insurance coverage for that 12-month period. If you're uninsured and living abroad under this definition, you qualify for a health insurance exemption. This means you don’t have to pay the fee that other uninsured people must pay."
It also links to an IRS webpage for further clarification.