Glazing Scope of Work: Curtain Wall Performance, IGUs, and Perimeter Sealants
What to put in a glazing scope of work — AAMA performance grades, IGU and Low-E specs, structural silicone, anchor coordination, AAMA 501.2 water testing, and the perimeter sealant gap.
Glazing is the building envelope trade with the highest performance and code compliance exposure on most commercial construction projects. Curtain wall systems, storefront, window wall, entrances, and specialty glazing all require precise coordination with the structural engineer, waterproofing sub, and the local energy and building codes. A glazing scope of work that leaves system performance requirements, thermal testing, installation tolerances, and sealant responsibility undefined will result in energy code failures, water infiltration, and warranty disputes. This guide covers the complete scope every PM and estimator needs.
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System Types, Glass Specs, and AAMA Performance Requirements
The line items that govern a glazing buy-out — system classification (storefront, window wall, curtain wall, SSG), AAMA air/water/structural performance grades, IGU and Low-E specifications, safety glazing, and entrance hardware must be explicit before shop drawings.
Glazing scopes must define the system type, performance criteria, and glass specifications before the RFP — not after shop drawings are submitted.
System Type and Structural Classification
Storefront: Thermally broken aluminum framing system for ground-floor commercial entries and punched openings. Spans between floor and ceiling. Standard commercial storefront is 2"×4.5" or 2"×6" face dimension. Specify framing finish (clear anodized, dark bronze, painted), glass type (see below), and door system (framed aluminum entrance, all-glass entrance).
Window wall: Similar to curtain wall but bears on the floor slab at each level rather than spanning between floors. Cost-effective for high-rise residential and mid-rise commercial where the structural system provides frequent bearing points. Specify system air/water/structural performance ratings per AAMA/WDMA/CSA 101/I.S.2/A440, thermal performance (U-factor), and solar heat gain coefficient (SHGC).
Curtain wall: Stick-built or unitized system that spans between floor slabs, bearing at each floor level via structural anchor plates. Unitized curtain wall is factory-assembled and installed in pre-glazed panels — shorter field installation time but requires precise structural tolerances and earlier anchor plate coordination. Specify the system type, anchor plate design, and who designs and installs the structural anchor plates (typically the glazing sub in coordination with the structural engineer). For mid-rise and high-rise applications, specify a CW or AW performance class per AAMA 101 (CW for mid-rise commercial, AW for architectural / high-rise).
Structural silicone glazing (SSG) / point-fixed glazing: Specialty systems for all-glass facades, canopies, and atriums. Require project-specific engineering. Structural silicone is the primary structural connection — curing time, thickness, and bite dimensions are critical to system performance. Require installer qualification for structural silicone application and ASTM C1401 compliance.
Glass Specification
Insulating glass unit (IGU): Standard for all commercial glazing. Specify spacer type (aluminum vs. warm-edge), gas fill (argon at 90% purity minimum), and total unit thickness. Typical commercial IGU: 1" overall (¼" glass + ½" air space + ¼" glass). Certify IGU per ASTM E2190 for durability.
Low-E coating: Required by ASHRAE 90.1 and most energy codes. Specify coating surface (position 2, 3, or 4 — position 2 is most common for heating-dominant climates; position 3 for cooling-dominant), SHGC value, and visible light transmittance (VLT). SHGC and U-factor must comply with the energy code for the project's climate zone and orientation.
Tempered and laminated glass: Safety glazing required in hazardous locations per IBC Section 2406: within 18" of the floor, within 24" of a door, in sidelites, and in wet areas. Specify tempered (ANSI Z97.1) or laminated (PVB interlayer, ≥0.030" per ANSI Z97.1) where required. Laminated glass is preferred for overhead glazing (skylights, canopies) where tempering alone does not prevent fall-out of broken glass.
Acoustically rated glass: For exterior glazing adjacent to high-noise environments (airports, highways, transit). Specify STC or OITC rating, interlayer type (PVB vs. SGP for higher acoustic performance), and thickness combination.
Bird-friendly glass: Required in some jurisdictions and by many institutional owners. Specify fritting pattern coverage (minimum 5% coverage with ≤2" × 4" clear panels) or ultraviolet-reflective glass (visible to birds, not humans).
Entrance Systems and Hardware
Commercial entrance doors: specify door type (all-glass (herculite), framed aluminum, automatic sliding, revolving), frame profile and finish, door width and height, door closer type (surface-mounted, concealed overhead, floor closer), and panic hardware where required by occupancy.
ADA compliance: confirm door opening force (max 5 lbs for non-fire-rated doors per ADA Standards Section 404.2.9), threshold height (max ½" per ADA), and maneuvering clearance at both sides of the door.
Automatic doors: powered sliding or swinging automatic entrances require an independent power source, sensor head coordination, and an activation mat or presence sensor. Specify sensor type, safety reversing requirement, and hold-open delay.
Tip for PMs: The most common glazing scope gap is the sealant at the perimeter of the glazing system. The glazing sub installs the system with a manufacturer-standard joint at the head, sill, and jambs. The perimeter sealant (the joint between the glazing frame and the adjacent wall, masonry, or cladding system) is frequently in a grey zone between the glazing sub and the waterproofing or sealant sub. Define this joint responsibility explicitly — it is the primary water infiltration path.
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Common Glazing Scope Gaps at Buy-Out
Items routinely left out of glazing sub bids — performance mock-up and AAMA 501.2 field water testing, anchor plates, perimeter sealant, window-washing tie-back anchors, and dead-load deflection coordination — that drive change orders if they're not nailed down.
Glazing submittals must demonstrate code compliance before fabrication — not after installation. Glass delivery lead times of 8–14 weeks make late submittal revisions extremely costly.
Required Submittals
Shop drawings: elevation views showing unit dimensions, glass type per lite, framing member sizes, anchor plate locations, expansion joint locations, and perimeter sealant joint detail
Performance test reports: AAMA 501, 502, or 503 testing for air infiltration, water resistance, and structural performance. For curtain wall systems, AAMA 501.1 dynamic water test or equivalent. Reports must be from an accredited laboratory for the specific system being installed.
Energy compliance documentation: U-factor and SHGC calculations for the overall fenestration assembly, not just the center-of-glass values. U-factor and SHGC must meet the energy code for the project climate zone and window-to-wall ratio.
Glass certification: ASTM C1048 for heat-treated glass; CPSC 16 CFR Part 1201 or ANSI Z97.1 for safety glazing; EN 12150 for European projects
Anchor plate design drawings stamped by a structural engineer, coordinated with the structural engineer of record
Mock-Up Requirements
A minimum 2-bay × 2-floor mock-up is required for all curtain wall and window wall systems before production begins. The mock-up must include: all joint types (horizontal and vertical), at least one anchor plate condition, one corner condition, and one door or operable unit if applicable.
The mock-up must be water tested (AAMA 501.2 field water test or equivalent) and reviewed by the architect, structural engineer, and waterproofing sub before production approval is granted.
Best Practices from Leading GCs
Issue structural slab edge drawings to the glazing sub at the earliest possible stage so anchor plate locations can be coordinated before the slab is formed. Late anchor plate additions to poured concrete slabs are extremely expensive.
For unitized curtain wall, require the glazing sub to provide a factory glazing schedule showing when each panel will be shipped. Delivery sequence must match the erection sequence — a mis-sequenced panel delivery on a unitized curtain wall project can shut down installation for weeks.
Include a thermal performance validation requirement in the scope: require a post-installation infrared thermography scan (ASTM C1060) of a sample bay to confirm there are no significant thermal bridges or missing sealant in the installed system.
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Glazing Coordination with Structural, Waterproofing, and Framing
Interface items between the glazing sub and the structural engineer, embed-plate fabricator, waterproofing sub, and back-up wall framing trade that must be defined upfront so anchor positions, dead-load deflection, and perimeter sealant responsibility are all settled before mobilization.
Glazing coordinates with structural (anchors and dead-load deflection), waterproofing (perimeter sealant), the back-up wall framing sub, and the façade cleaning/maintenance system (anchor points for suspended access equipment).
Structural and Anchor Coordination
Anchor plates embedded in or attached to the structural slab must be positioned within the glazing sub's specified tolerance — typically ±¼" in all three axes. Survey the slab edge and anchor plate positions before glazing installation and report any out-of-tolerance conditions before the glazing sub mobilizes.
Deflection limits: curtain wall systems are designed for the structural engineer's specified slab deflection. If the building's actual slab deflection exceeds the curtain wall system's allowable inter-storey drift, the system will distort under load. Confirm the design deflection envelope is shared between the structural engineer and the curtain wall engineer of record. Typical inter-storey drift limit is H/400 for serviceability; AAMA 501.4 provides the dynamic racking test for seismic regions.
Waterproofing and Perimeter Sealant
The joint between the glazing system and the adjacent construction (masonry, EIFS, metal panel, concrete) is the primary water infiltration risk on every commercial facade. Specify a high-performance silicone or polyurethane sealant (ASTM C920, Type S, Grade NS, Class 35 minimum) at all perimeter conditions. Define whether this is the glazing sub's scope or a separate sealant/waterproofing sub's scope — and require a single point of responsibility to avoid disputes.
Flashing at sill conditions: confirm that sill flashing and weep holes at the base of each glazing bay are included in either the glazing sub's scope or the waterproofing sub's scope — not in neither.
Back-up wall coordination: where the glazing system jambs into stud-framed back-up walls, confirm that the framing sub has installed structural cold-formed studs at the head and jamb conditions sized for the curtain wall anchor reactions — not just standard partition studs.
Pre-Installation Coordination Checklist
Anchor plate survey complete — positions confirmed within tolerance
Structural slab edge drawings coordinated with glazing sub
Shop drawings submitted, reviewed, and approved
Mock-up constructed and water test passed
Energy compliance documentation submitted to building official
Perimeter sealant responsibility defined in both glazing and adjacent trade scopes
Delivery sequence plan received and integrated into schedule
Scaffold or MCWP configuration confirmed for glazing platform requirements
Tip for Estimators: When reviewing a glazing bid, check whether anchor plates, structural silicone, perimeter sealant, and window washing anchor points are included. These items are consistently excluded from glazing bids that price "supply and install of curtain wall system only." On a large facade, anchor plates and perimeter sealant alone can add 8–15% to the glazing contract value.
Glazing Scope of Work — FAQ
Whose scope is the perimeter sealant — glazing sub or waterproofing/sealant sub?
This is the single biggest scope gap on glazing buy-outs. The glazing sub installs the system with manufacturer-standard joints inside the framing; the perimeter sealant (the joint between the glazing frame and adjacent masonry, EIFS, metal panel, or concrete) is the primary water infiltration path and frequently sits in a grey zone. Best practice: assign the perimeter sealant explicitly to the glazing sub so there is one party responsible for water performance of the entire glazing assembly, including the transition to adjacent construction. Specify ASTM C920 Type S, Grade NS, Class 35 minimum sealant.
What AAMA performance class should I specify for a mid-rise office curtain wall?
For most mid-rise commercial buildings (4–15 storeys), specify AAMA/WDMA/CSA 101/I.S.2/A440 CW class (Commercial) with a design pressure rating matching the project's wind load (typically DP-40 to DP-60). For high-rise (over 15 storeys) or architectural projects, specify AW (Architectural Window) class — it has the most stringent air, water, and structural performance requirements. Include AAMA 501.1 dynamic water test for unitized curtain wall and AAMA 501.4 seismic racking test in seismic design categories D, E, and F.
Are anchor plates in the glazing sub's scope or the structural steel/concrete scope?
Anchor plates are engineered by the curtain wall engineer of record but supplied and installed by different trades depending on the substrate. Cast-in anchor plates set in concrete slab edges are typically supplied by the glazing sub (or via the curtain wall engineer) and installed by the concrete sub before the pour. Welded-on anchor plates to structural steel are typically in the structural steel scope using the glazing sub's drawings. Specify which model applies and require the anchor layout to be on the structural drawings — not just the curtain wall shop drawings.
When is AAMA 501.2 field water testing required?
AAMA 501.2 is a low-pressure spray test for installed glazing systems using a calibrated nozzle. Specify it for the mock-up panel before production approval and for a sample of installed bays after installation (typically 1 bay per 10,000 sq ft of glazing, minimum 3 bays). For curtain wall on high-rise or architectural projects, specify AAMA 501.1 dynamic test on the lab mock-up plus 501.2 field testing. State who pays — typically the glazing sub for the mock-up tests and the GC for additional field tests, but this must be explicit.
What's the typical glass lead time and how does it affect submittal sequencing?
Commercial IGU with Low-E coating and warm-edge spacer is typically 8–14 weeks from approved shop drawings to delivery. Tempered, laminated, or oversized lites add 2–4 weeks. Custom frit patterns or specialty coatings can add 6+ weeks. Sequence shop drawing submittal so approved drawings reach the fabricator at least 16 weeks before the first glazing installation. A delayed submittal cascade is the most common cause of glazing-driven schedule slip on commercial projects.
What's the most common glazing scope gap on a unitized curtain wall buy-out?
Tie-back anchors for window-washing equipment (Building Maintenance Unit / suspended access). These anchors must be coordinated with the structural engineer, located on the curtain wall shop drawings, and either supplied by the glazing sub or by a separate facade access contractor. They are routinely missed at buy-out and discovered during commissioning. Other common gaps: structural silicone field labor, perimeter sealant, sill flashing terminations, and the cost of mock-up testing.
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