Searching the reference manual for 2.1 I don't believe SHAPE = POLYGON is an option.
Here is the entry for the SPACE keyword SHAPE in 2.1e:
SHAPE - is an alternative method for defining a space. It is
simpler than using the space coordinate system. At present
there is only one shape -- BOX. This box is defined by the
HEIGHT, WIDTH, and DEPTH keywords and the faces of the box
are defined internally. The faces can then be referred to by
instructions that define their nature (i .. e. EXTERIOR-WALL).
Fig. 111.6 shows how a BOX and its faces are defined with
respect to the space coordinate system.
In the 2.2 reference manual Vol-1 "Basics", I found the following quote, suggesting POLYGON space geometry definitions were a "new" thing as of 2.2:
There are very few changes in the LOADS input from previous program versions, except for the FLOOR command, the specification of lighting systems, and the specification of shapes for floors, spaces, and walls using polygons.
(emphases mine)
I think you have 2 options:
In 2.1e, a SPACE can specify SHAPE = BOX, then the associated HEIGHT, WIDTH, DEPTH. This permits its child surfaces to simply specify LOCATION (LEFT/RIGHT/FRONT/BACK/TOP/BOTTOM).
It's my impression that your only alternative is to NOT use the SHAPE keyword at all, thus requiring AREA/VOLUME to be specified for each space in lieu of HEIGHT/WIDTH/DEPTH, and requiring each child surface to specify X/Y/Z/AZIMUTH/HEIGHT/WIDTH in lieu of LOCATION.
A qualifier: 2.1e is mostly before my time - I only really got started in the simulation world with 2.2. Others better qualified to answer might be more easily reached by cross posting into the [eQUEST-users] mailing list at onebuilding.org, but if you should need help identifying someone for a cold call let me know and I'll help point you in the right direction!
Thinking forward: If you don't want to script out the math to determine each floor polygon's area - it sounds as though you might have a doe 2.2/2.3 project handy which you could open up in eQUEST, navigate to Building Shell -> Spreadsheet view for spaces, then sort the spreadsheet view by Polygon Assignment. Area for each polygon used for SPACE shapes appears 2 columns to the right.
If you are additionally using polygons in lieu of simpler methods to specify building shades, PV Arrays, or specially shaped interior/exterior/underground surfaces (hard to do these by accident if you are used to leveraging the wizards), you'd need to seek those out separately, but in a similar fashion using the spreadsheet views.
I hope this helps - best regards!
~Nick