My question is still the same: is he eligible to claim the full exemption?. Just to make the situation clear:

Ownership: Year 1-4, 4yrs total

Residency: Year 1-4, 4yrs total (temporary absence for 9 months in yr 3 due to change of employment)

Rental(part of home): Year 2-3, 2 yrs total

Rental income and expenses were correctly reported when he rent out part of his home.

I believe Bill just answered. Your advice is greatly appreciated too!