Commercial Curtain Wall Reglaze: In-Place vs Full Replacement

Why this matters

A 1980s aluminum stick-system curtain wall with failed insulating glass units (foggy units, broken edge seals, condensation at the spacer) presents the building owner with a binary choice with a 5-to-1 cost spread: reglaze the existing frame (cut out the failed IG, install a new IG into the existing pocket) or full system replacement (tear out frame to slab edge, install a modern unitized or stick system). The right answer depends on the frame's structural condition, the existing thermal break (or lack of it), code-required performance under ASHRAE 90.1 or the local IECC, glazing pocket geometry, and the building's occupancy continuity tolerance. Picking the wrong path produces either a reglaze that fogs again in 5 years or a full replacement that was not actually needed. This reference is the decision framework.

Initial frame condition assessment

Before any glazing scope is priced, the existing frame is assessed against four pass/fail criteria:

1. Frame structural integrity. Aluminum extrusions corrode through galvanic action where dissimilar metals contact (steel fasteners, anchor clips). Probe-test every transom and mullion at anchor points. Visible pitting, white corrosion bloom, or section loss at anchors disqualifies reglaze. ASTM E330 structural performance testing on a representative bay is the gold standard but rarely done; visual is the field call.
2. Thermal performance baseline. Pre-1990 stick systems are almost always thermally unbroken aluminum (no poured-and-debridged or pressure-plate thermal break). Frame U-factor is typically 1.0 to 1.5 BTU/(hr.sq ft.F) regardless of glass. New code (ASHRAE 90.1-2022 Table 5.5 or IECC 2021 Table C402.4) requires whole-window U-factor at 0.38 to 0.45 BTU/(hr.sq ft.F) depending on climate zone. A reglaze with the existing thermally-unbroken frame cannot meet code; the frame component dominates the assembly U-factor.
3. Glazing pocket compatibility. New IG units have evolved. Pre-1990 pockets typically accept 1 in IG (1/4 - 1/2 air - 1/4); modern high-performance IG runs 1-1/4 in to 1-3/8 in to accommodate triple glazing or wider warm-edge spacers. Measure the existing pocket internal dimension; if it is less than 1-1/16 in you are limited to glass thicker than the original but with a thinner air space or you cannot retrofit modern IG at all.
4. Sealant condition. Original wet glazing was typically a polysulfide or first-generation silicone with 15 to 20 year service life. Pre-1990 sealants are at or past end-of-life and reglaze removes and replaces the sealant by definition. Verify the existing structural silicone is not bearing dead load on the IG; some 1970s units use structural sealant the original spec did not call out.

Reglaze: when it makes sense

Reglaze is the right answer when:

1. Frame is intact, anchors corrosion-free, thermal break salvageable.
2. IG-only failure drives the work, not envelope performance.
3. Occupancy continuity is critical. Reglaze runs unit-by-unit off-hours; the tenant sees a one-bay swap on a Saturday, not weeks of exposed slab edge.
4. Permit appetite is low. Reglaze is a glazing permit only; full replacement is an envelope permit with energy-code commissioning, possible facade-inspection-program filing (NYC FISP, Chicago Facade Ordinance), and structural review.

Reglaze technical scope:

• Remove pressure plate (for pressure-glazed) or cut wet seal (for structural-glazed).
• Lift out failed IG. Stick-system IG weighs 80 to 200 lb; removal from inside is standard above grade. Vacuum lifter and two-glazier crew minimum.
• Inspect glazing pocket, clean, prime as required.
• Install new IG to manufacturer edge-bite and clearance spec (Vitro Solarban 70XL, Cardinal LoE-180 / LoE-272, Pilkington Optifloat with Suncool coating). Setting blocks at quarter points.
• Reinstall pressure plate or apply new structural sealant (Dow Corning 795, Sika SikaSil SG-500, Pecora 895). Cure before water test per the sealant TDS.

Full replacement: when it makes sense

Full replacement is right when:

1. Frame is corroded at anchor points or shows section loss at any structural element.
2. Energy code triggers force whole-assembly compliance (more than 50% of wall area replaced; verify with the AHJ under IECC 2021 Section C402).
3. Building is repositioned (Class B office to residential or boutique hotel) and the owner wants a modernized facade.
4. Water-test history shows persistent leaks not attributable to IG seals; gasketry, weep system, or thermal break is failing.

Full replacement technical scope:

• Engineering: licensed structural engineer for the new anchor system to the existing slab edge.
• Mockup: ASTM E283, E331, E330 on a representative bay; AAMA 501.1 / 501.2 dynamic water test if the building has known issues.
• Phased occupancy: two-bay-wide horizontal stripe at a time, night closure via temporary glazing or interior poly with floor evacuated for the day.
• System: unitized (factory-assembled, faster on site, requires crane) vs. stick (field-assembled, slower, tighter access).
• Energy commissioning: ASHRAE 90.1 Section 4 documentation, NFRC-labeled performance, blower-door if the local code requires it.

Decision matrix summary

Common errors

1. Reglazing a thermally-unbroken frame and selling LoE3 glass as an "energy upgrade." Frame dominates U-factor; the claim is not defensible per NFRC 100.
2. Specifying triple-glazed IG into a 1 in pocket. Will not fit.
3. Skipping structural-engineer review on full-replacement anchor retrofit. The new anchor system carries new load paths to the existing slab edge.
4. Reglazing without addressing perimeter sealant at slab edge and parapet. Water continues to leak; owner blames the new IG.

References

1. AAMA / WDMA / CSA 101 / I.S.2 / A440-22, NAFS North American Fenestration Standard (curtain-wall classification and performance).
2. ASHRAE 90.1-2022, Energy Standard for Buildings Except Low-Rise Residential Buildings, Section 5 (Building Envelope), Table 5.5.
3. IECC 2021, Sections C402.4 (Fenestration) and C503 (Alterations).
4. ASTM E283-19, Standard Test Method for Determining Rate of Air Leakage Through Exterior Windows, Curtain Walls, and Doors.
5. ASTM E330-14, Standard Test Method for Structural Performance of Exterior Windows, Doors, Skylights and Curtain Walls.
6. AAMA 501.1-17 and 501.2-15, dynamic and field water-resistance test methods.
7. NFRC 100-2020, Procedure for Determining Fenestration Product U-factors.
8. Vitro Solarban 70XL Technical Data Sheet and Cardinal LoE-180 / LoE-272 product literature.