A 12-story, 240,000 sq ft office building case study — retrofitting a mixed pneumatic/obsolete-DDC building with a modern BACnet/IP BAS: phased supervisory-front-end-first capital planning, worked AHU/VAV sequence changes, commissioning findings, and projected-versus-actual energy savings.
The project brief: a 1978-built, 12-story office building running half on original pneumatic controls and half on a discontinued proprietary DDC platform needs a full BAS retrofit before a planned leasing push — with no budget or tenant tolerance for a single 14-month rip-and-replace mobilization. The retrofit is phased instead: a BACnet/IP supervisory front-end and legacy protocol gateways first, for visibility before capital is committed to field-device replacement, then pneumatic-to-DDC conversion, then AHU and plant sequence optimization.
This module walks the whole retrofit the way a real controls engineer would: a worked existing-conditions assessment quantifying the pneumatic and legacy-DDC failure rates, the phased capital plan and why the phase order matters, a worked AHU economizer and static-pressure trim-and-respond sequence rewrite, commissioning findings from trend-log review, and a full accounting of why measured savings came in under the projection. The complete points list, bill of materials, and finished design reasoning are part of the unlocked module below.