Design-assist, delegated design, and design-build are three different ways a contractor contributes to HVAC design — distinguished mainly by who holds the engineer-of-record seal and who owns the design. In design-assist the engineer keeps the seal and the contractor advises; in delegated design the engineer assigns specific portions to the contractor under their seal; in design-build the contractor owns the design and either self-performs it within license limits or carries its own PE of record.
In design-assist, the owner retains a mechanical engineer of record, and the contractor joins the design team early to contribute constructability, equipment, controls, and cost reality. The engineer keeps the seal and the design responsibility; the contractor’s input makes the design buildable.
This fits owners who want an independent engineer but also want a builder’s perspective before the set is finalized. It is the model on our engineer partner page.
Delegated design is when the engineer of record assigns specific, well-defined portions of the design to a specialty contractor under a performance specification — commonly controls sequences, or shop-level coordination. The contractor develops those portions, and they are reviewed and accepted under the engineer’s seal.
It keeps the engineer responsible for the overall system while leveraging the contractor’s detailed expertise on a defined scope.
In design-build, the contractor owns both design and construction under one contract. Below the Florida contractor self-design thresholds, the Class A contractor performs the design itself; above them, the design-builder carries its own Professional Engineer of record for the sealed work.
The owner signs one contract and holds one party accountable for the result. See what a Florida Class A contractor can legally design.
The cleanest way to tell these apart is to ask who holds the seal and the design liability. Design-assist and delegated design: the owner’s engineer of record. Design-build: the design-builder (self-performed within limits, or via its PE of record).
A reputable contractor is explicit about this on every engagement, because the seal boundary is also the liability boundary.
Choose design-assist when you value an independent engineer but want buildability input. Choose delegated design when your engineer wants to keep overall responsibility but hand off a defined scope. Choose design-build when you want one accountable party, faster schedule, and earlier cost certainty.
The same firm can serve all three roles — what changes is the contract structure and where the seal sits. Design-build vs design-bid-build covers the broader delivery question.
In design-assist, the owner keeps a mechanical engineer of record who holds the seal, and the contractor advises during design. In design-build, the contractor owns the design and construction under one contract — self-performing design within license limits or carrying its own PE of record.
Delegated design is when the engineer of record assigns specific, defined portions of the design — often controls sequences or shop coordination — to a specialty contractor under a performance spec, reviewed and accepted under the engineer’s seal.
In design-assist and delegated design, the owner’s mechanical engineer of record. In design-build, the design-builder — either self-performed within the Florida Class A contractor thresholds, or via the design-builder’s own Florida PE of record.
Yes. The same firm can provide design-assist, delegated design, or full design-build; what changes is the contract structure and where the seal and design liability sit. Each engagement should define that boundary in writing.
Suncoast Cold Systems delivers commercial HVAC design-build across Tampa, St. Petersburg, Clearwater, Brandon, Riverview, Temple Terrace, and Wesley Chapel — load calcs, equipment selection, layouts, controls, install, and commissioning under one contract. Licensed Class A A/C Contractor (FL #CAC1824642), with a Florida PE of record on sealed work.
The seal boundary, in statute.
The broader delivery-method decision.
Design-assist and delegated design under your seal.