In order to qualify for ENERGY STAR certification, all homes must meet an overall efficiency target. Builders are allowed to mix and match upgrades until they hit this target. This generally does not require the use of ENERGY STAR certified equipment, windows, doors, roof products, lighting, or appliances. In practice, however, many builders elect to include such products as a cost-effective strategy for meeting the overall efficiency target.
A more thorough explanation of the ENERGY STAR homebuilding requirements can be found here.