Curtain Wall Submittal Conflict on a Mid-Rise
A five-story, 90,000 sf office building uses a unitized curtain wall with a specified U-value of 0.38 and a project requirement for continuous air barrier. The glazing subcontractor submits shop drawings showing a stick-built system with field-applied sealant at the slab edge, a 0.42 U-value, and no continuous transition membrane at the floor line. The architect's spec references a performance requirement but the drawings show a generic detail. The schedule has 6 weeks of float before the envelope must be watertight, and the window order lead time is 14 weeks. The owner's commissioning agent has flagged air infiltration testing at 0.25 cfm/sf as a closeout requirement.
1. Is this submittal a substitution, a nonconformance, or a clarification? What action do you take and in what sequence?
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It is all three at once, and the sequence matters because of the 14-week lead time.
Against the spec, the 0.42 U-value fails the 0.38 requirement, so it is a nonconformance. The switch from unitized to stick-built is a substitution because it changes the system type and the installation sequence. The missing transition membrane at the floor line is a clarification issue that also threatens the 0.25 cfm/sf infiltration test.
Sequence: first, issue a formal review comment rejecting the U-value and the missing air barrier transition, and request a revised submittal within five working days so the window order is not delayed. Second, require the subcontractor to submit a substitution request with engineering justification if they want the stick-built system, including a mockup and a performance path to the infiltration target. Third, notify the owner and commissioning agent in writing of the potential schedule impact so the float is not silently consumed.
Do not approve 'as noted' on a U-value miss; that converts a clear rejection into a disputed directive.
2. The subcontractor argues the 0.25 cfm/sf test is stricter than code and should be waived. How do you evaluate that claim?
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Treat the claim as a contract question, not a technical one, and answer it on the record.
Code minimums for envelope air leakage are typically looser than a project-specific commissioning target, so the subcontractor may be correct that 0.25 cfm/sf exceeds code. But the contract documents, not the code, define the acceptance criteria, and the commissioning requirement was in the bid documents. A bidder who did not take exception at bid time generally owns the requirement.
The practical evaluation: can the proposed system meet 0.25 cfm/sf with proper detailing? A stick-built system can meet tight targets if the air barrier is continuous at slab edges, penetrations, and transitions. The failure mode is usually the floor-line detail, which is exactly what is missing. So the test is achievable; the submittal is deficient.
Recommendation: hold the criterion, require a revised detail and a mockup test of a representative bay before full release of the window order. If the mockup fails, then discuss a variance with the owner, backed by test data. Waiving the requirement before testing gives away the owner's leverage and yours.