Mike,

If you have the as-built drawings, as you mentioned, then you should set
the model up using the actual building and equipment efficiency values
from your building drawings, that are confirmed by any site visits,
rather than using the default values in the program, which are typically
minimum energy code requirements, as you mention. You should be able to
then do base model runs that approximate the existing building's actual
2-3 year average energy usage. Of course, you might have to adjust your
model to get it to match the actual historical energy usage of the
building within 1-2%, unless you are not required to have that close of
accuracy. Any way, yes, a 12 year old building likely would have higher
energy usage than one built meeting to today's energy code requirements,
that is, of course, unless the building 12 years ago was built to a
standard that was better than the present energy code.

Regards,
David A. Bastow