This isue can be very confusing when it comes to detail.
1.
Gross floor area (based on ASHRAE definition) sais that the calculation "excludes floor area dedicated to the parking and circulation of motor vehicles". Typically, on underground parking floors, there are rooms with other usage type.
In our project (Retail and Office-Mixed Use) there is a 3-storey underground parking lot with circulation, but there are also technical rooms (AHU, utility connections, chillers), vertical communication (stairways), changing rooms and showers for bicycle users, stuff rooms, storage rooms etc. Usable floor area of these rooms should be substracted from gross floor area calculation and include only parking places with circulation (exterior faces of exterior walls)?
2.
It also sais that the calculation "excludes air shafts, pipe trenches, and chimneys". Does this also apply to internal shafts and chimneys (clear dimensiohttp://www.leeduser.com/sites/all/themes/leeduser/images/form-submit.gifns) and each should be substracted from the gross floor area calculation?