Late Air-Handling Unit Substitution on the Critical Path
Six weeks after notice to proceed on a $12 million school renovation, the mechanical contractor requests substitution of the specified ABC-40 air-handling unit with an XYZ-40 model. The substitution is submitted under Section 01 25 00, which requires requests within 15 calendar days after notice to proceed. The contractor says it needed time to compare energy performance. The proposed unit has the same capacity and dimensions but a 4-week longer lead time and an IEER 0.8 lower than the specified unit. The contract includes a completion date with $2,500 per day liquidated damages. The contractor states the substitution will save $38,000 and asks for a change order giving it the savings. The specified unit's submittal was approved 10 days ago; the current schedule shows the air-handling unit installation on the critical path with zero float. The architect's submittal review is not complete for the mechanical package.
1. How should the architect and CA process the substitution request on timeliness?
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The first issue is procedural. Section 01 25 00 requires a substitution request within 15 calendar days after notice to proceed; this request came at day 42. The contractor's explanation of needing time to compare energy performance is not a good-cause justification because the information was available at bid time. The architect may reject the request as untimely and return it without technical review.
However, the CA should not ignore the request entirely: acknowledge it in writing, state the contractual basis for rejection, and copy the owner. If the contract allows late consideration for good cause, the architect should decide that expressly; the CA should not waive the deadline informally. The CA should also check whether the contractor is actually claiming the specified unit is unavailable; if so, that is a different product-availability issue that must be documented.
2. Evaluate the technical and schedule merits of the proposed substitution.
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On the merits, the proposed unit is not clearly equal. Same capacity and dimensions are necessary but not sufficient; an IEER 0.8 lower may violate the specified minimum efficiency and will increase operating cost. The 4-week longer lead time is more serious because the air-handling unit is on the critical path with zero float and the contract carries $2,500 per day liquidated damages. A $38,000 first-cost savings can be consumed by 16 days of delay, before considering energy and warranty effects.
The contractor is not entitled to keep the savings; if a substitution is accepted, the net savings belong to the owner because the contract sum was based on the specified unit. The CA should recommend rejection unless the owner and design team conclude that the unit meets performance requirements and the schedule can be protected by a recovery plan.
3. If the owner wants the $38,000 savings, how should the change order be structured?
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If the owner nevertheless wants to pursue the substitution, do not issue a verbal approval. Require a formal change order with: the exact product and performance data; an owner-approved credit for the net savings, including the specified unit's contract value less the proposed unit's cost; a revised schedule showing how the 4-week lead time will be recovered without affecting the completion date; a waiver of any contractor claim for delay caused by the substitution; and confirmation that the unit meets the specification or a written modification of the performance requirement.
The CA should also require updated submittals, warranty, and commissioning data. If the contractor cannot protect the completion date, the owner should retain the specified unit and the CA should document the schedule risk.