Establish the original requirement, identify the exact proposed product or assembly and compare performance, geometry, supports, utilities and maintenance access. Record departures and required decisions before treating the proposal as an accepted change.
Define the proposal before comparing it
Record the proposed model, material, system boundary and exclusions. An unmarked catalog does not establish which option is offered. Ask for the evidence needed to compare the proposal with the issued design.
Keep the commercial proposal alongside the technical comparison, but use separate fields. A quoted saving does not establish conformance with the specification, and a coordinated proposal does not establish its final installed cost.
Compare like with like
Check the operating condition, rating basis and required accessories behind each value. A capacity quoted under a different condition may not answer the specification’s requirement. Where the basis is unclear, identify the missing evidence rather than assuming equivalence.
The design criteria guide helps trace the owner requirement into the design. Keep any proposed departure visible for the person authorized to approve it.
A hypothetical equipment substitution
Suppose a proposed rooftop unit has the required duty but a different weight, connection location and electrical requirement. Compare its support and curb with the structural and roof details, then compare power, controls and maintenance access with the other disciplines.
A useful question identifies the proposed selection and the dependent documents that still describe the original unit. The team can then obtain a coordinated design response and assess the actual cost of the additional work.
Substitution comparison worksheet
| Check | Sources | Review question |
|---|---|---|
| Original basis | Issued drawings, specifications and owner criteria | Which requirements must the proposal satisfy? |
| Proposed selection | Marked product data, assembly and exclusions | Is the actual product and option clearly defined? |
| Comparable performance | Specified criteria and proposed ratings | Are the values based on compatible conditions and test methods? |
| Geometry | Dimensions, receiving detail and clearance | Does the proposed item fit the documented location and access? |
| Support | Proposed loads, anchorage and structural details | Does the receiving support agree with the proposed selection? |
| Services and controls | Power, connections, sequences and schedules | What changes are required in the connected systems? |
| Approval path | Deviation list and project procedure | Who must accept each departure and which evidence is required? |
| Design reconciliation | Accepted decision and revised documents | Did the authorized change reach every dependent source? |
Use evidence from the whole package
The apartment HVAC case shows equipment assignments and ventilation information that needed reconciliation. It illustrates the documents a proposed equipment change can affect; the case does not claim a VE proposal caused those findings.
Follow the accepted decision into drawings, schedules, specifications and procurement instructions. Retain superseded selections so the next reviewer can understand why the current package differs.
Source and review boundaries
UFGS 01 33 00 provides one public example of submission procedures; use your project’s actual substitution and approval requirements. Source checked October 13, 2026.
A drawing-to-specification review can help surface conflicts in the supplied evidence. The project’s designers and authorized parties decide technical acceptability, scope and price.