Additions to existing buildings

Would an addition of floor area inside an existing building shell be considered an addition to an existing building therefore requiring compliance with the "new building" threshold for reduction in energy cost? According to ASHRAE 90.1-2007 an addition is considered as "an extension or increase in floor area or height of a building outside of the existing building envelope." Hence, the case described above does not fall under the "new building" threshold, does it? Has anyone experienced a similar situation? Thank you in advance.