Design-build against the owner's project requirements
Bidding a finished set of documents and bidding an owner's criteria are two different transactions, and the difference shows up in who owns the unknowns. In a plan-and-spec job the district pays an engineer to produce a coordinated, stamped design, then asks contractors to price exactly that. Anything the drawings got wrong about the building comes back as a change order.
Here the district issued criteria instead: owner's project requirements in the form of technical specifications, schematic drawings, and record drawings for each of the three buildings. Record drawings are a description of what somebody intended decades ago, not a survey of what is in the mechanical room today, and pricing against them means accepting the gap. On three buildings with three different histories — thermal storage tanks at two, an indoor chiller with a cooling tower, a heat recovery chiller and a vertical turbine pump in a pit at the third — that gap is not small. Design-build moves it to the design-builder before the number is set, which is what a district is actually buying.
The method also decides sequence, and this contract writes the sequence into two dates. Heating hot water is substantially complete by September 1, 2024; chilled water and temperature controls by March 31, 2025. Nobody would phase it that way to make construction convenient. It is phased that way because a school needs heat in September more than it needs chilled water, and the cooling plant can take the winter to come together as long as it is running before spring. Setting those dates required knowing what could be staged, and that knowledge sits with the party doing both the design and the work.
The same logic applies across the trades. The LON-to-BACnet conversion touches mechanical, electrical and controls work in every building, and replacing a control network while replacing the equipment it controls is mostly a coordination problem. Design-build puts that under one signature.
Where we proposed changing the district's criteria
The most useful thing about design-build is not speed. It is that a contractor who disagrees with the owner's criteria can say so in writing, before construction, and let the district decide. This contract carries a list of modifications from the district's original criteria documents, and each one is a decision the district got to make in advance instead of receiving as a request for information in month four.
Some of them save money on work that would not have accomplished anything. The criteria called for balancing unit ventilator airflow; those units have no means of airflow adjustment, so a balance report on them would have been a document, not a result, and it came out. Others add. Boiler spare parts were provided beyond specification — two sets of manufacturer-recommended parts, alongside condenser fan motors, glycol and a storage cabinet — because a district that runs its own boilers is better served by parts on a shelf than by a spare filter list, which is also why spare air handler filters and fan belts came off.
The control wiring modification is the one worth studying. Rather than a blanket reuse or a blanket replacement, the contract sets a rule: existing temperature control wiring is reused only where the run is whole from the sensor location through the electrical trough to the terminal block, with no wire nuts and no junctions; anything spliced is replaced. Network wiring is demolished and replaced with BACnet regardless. Blanket reuse buys a district years of intermittent faults nobody can find; blanket replacement buys pulling good wire back out of the walls. The rule is the answer, and the district approved it before anyone opened a ceiling.
Two more are risk management. No upgraded service was requested from the electrical utility; the existing distribution was modified instead, using a spare 400-amp bucket in existing switchgear at one building and a tap off the existing main disconnect at another. Utility upgrades set schedules a construction contract cannot control. And a microchannel condenser coil was proposed in lieu of copper and aluminum tube-fin — recorded in the contract, and the district's call to accept.
