1 Scope
NOTE This standard governs the furnishing, fabrication, and installation of aluminum-framed glazed curtain wall as the primary non-load-bearing exterior enclosure of a building. (1.1)
1.2The work shall include the extruded aluminum framing (mullions, transoms, pressure plates, and covers), the thermal break, the glazing infill and its retention, the perimeter and intermediate seals, the anchorage back to the building structure, and the continuity of the air and water control layers across the curtain wall perimeter.
1.3The curtain wall elevations, mullion grid, design wind pressures, floor-line and anchor locations, glass types, and spandrel locations shall be as indicated on the contract drawings. 1.4This standard establishes the minimum performance, material, fabrication, and installation requirements applicable to all of those conditions.
NOTE A curtain wall is defined by what it does structurally: it carries no building floor or roof load, it spans vertically across one or more stories, and it transfers only its own dead weight and the wind load acting on its surface back to the building structure at discrete anchors. This is the property that separates a curtain wall from a storefront (supported on the slab at its base and typically one story tall) and from a window wall (which stacks within each story between the slab above and the slab below). (1.5)
NOTE Because the curtain wall hangs across the slab edge, it must simultaneously resist wind, exclude water and air, control heat flow and condensation, and accommodate the building's movement — floor live-load deflection, thermal expansion, and seismic interstory drift — without cracking glass, fracturing seals, or losing anchorage. Every performance category cross-couples to the others, and the wall shall be treated as a single engineered system. (1.6)
NOTE The curtain wall scope ends at the glass and at the perimeter seal. (1.7)
1.8The glass and insulating-glass-unit requirements — heat treatment, load resistance, coatings, laminated makeups, spandrel frit, and IGU durability — are governed by Glazing and are referenced, not duplicated, here. 1.9The continuity of the building air barrier into the curtain wall perimeter shall be coordinated with Air Barriers. 1.10The perimeter joint sealants shall be coordinated with Joint Sealants. 2 Referenced Standards
2.1Materials, fabrication, performance testing, and installation shall comply with the latest adopted edition of the referenced standards.
2.2Where the contract documents or the adopted building code impose more stringent requirements than a referenced standard, the more stringent requirement shall govern.
2.3The Contractor shall resolve conflicts in writing with the Engineer of Record before proceeding.
2.4 Referenced Standards List
| Standard |
Title |
| AAMA/WDMA/CSA 101/I.S.2/A440 |
North American Fenestration Standard (NAFS) — Specification for Windows, Doors, and Skylights |
| AAMA CW-10 |
Care and Handling of Architectural Aluminum from Shop to Site |
| AAMA CW-13 |
Structural Sealant Glazing Systems |
| AAMA CW-RS-1 |
The Rain Screen Principle and Pressure-Equalized Wall Design |
| AAMA 501 |
Methods of Test for Exterior Walls |
| AAMA 501.1 |
Standard Test Method for Water Penetration of Windows, Curtain Walls and Doors Using Dynamic Pressure |
| AAMA 501.2 |
Quality Assurance and Diagnostic Water Leakage Field Check of Installed Storefronts, Curtain Walls, and Sloped Glazing Systems |
| AAMA 501.4 |
Recommended Static Test Method for Evaluating Window Wall, Curtain Wall, and Storefront Systems Subjected to Seismic and Wind-Induced Inter-Story Drift |
| AAMA 501.5 |
Test Method for Thermal Cycling of Exterior Walls |
| AAMA 501.6 |
Recommended Dynamic Test Method for Determining the Seismic Drift Causing Glass Fallout from a Wall System |
| AAMA 501.7 |
Recommended Static Test Method for Evaluating Curtain Wall and Storefront Systems Subjected to Vertical Inter-Story Movement |
| AAMA 503 |
Voluntary Specification for Field Testing of Newly Installed Storefronts, Curtain Walls, and Sloped Glazing Systems |
| AAMA 507 |
Standard Practice for Determining the Thermal Performance Characteristics of Fenestration Systems in Commercial Buildings |
| AAMA 611 |
Voluntary Specification for Anodized Architectural Aluminum |
| AAMA 1503 |
Voluntary Test Method for Thermal Transmittance and Condensation Resistance of Windows, Doors, and Glazed Wall Sections |
| AAMA 2604 |
Voluntary Specification, Performance Requirements and Test Procedures for High Performance Organic Coatings on Aluminum Extrusions and Panels |
| AAMA 2605 |
Voluntary Specification, Performance Requirements and Test Procedures for Superior Performing Organic Coatings on Aluminum Extrusions and Panels |
| ASTM B221 |
Standard Specification for Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes |
| ASTM E283 |
Standard Test Method for Determining Rate of Air Leakage Through Exterior Windows, Curtain Walls, and Doors Under Specified Pressure Differences |
| ASTM E330 |
Standard Test Method for Structural Performance of Exterior Windows, Doors, Skylights, and Curtain Walls by Uniform Static Air Pressure Difference |
| ASTM E331 |
Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference |
| ASTM E1105 |
Standard Test Method for Field Determination of Water Penetration of Installed Exterior Windows, Skylights, Doors, and Curtain Walls, by Uniform or Cyclic Static Air Pressure Difference |
| ASTM E1300 |
Standard Practice for Determining Load Resistance of Glass in Buildings |
| ASTM E1886 |
Standard Test Method for Performance of Exterior Windows, Curtain Walls, Doors, and Impact Protective Systems Impacted by Missile(s) and Exposed to Cyclic Pressure Differentials |
| ASTM E1996 |
Standard Specification for Performance of Exterior Windows, Curtain Walls, Doors, and Impact Protective Systems Impacted by Windborne Debris in Hurricanes |
| ASTM E2190 |
Standard Specification for Insulating Glass Unit Performance and Evaluation |
| ASTM C1135 |
Standard Test Method for Determining Tensile Adhesion Properties of Structural Sealants |
| ASTM C1184 |
Standard Specification for Structural Silicone Sealants |
| ASTM C1401 |
Standard Guide for Structural Sealant Glazing |
| ASTM C920 |
Standard Specification for Elastomeric Joint Sealants |
| NFRC 100 |
Procedure for Determining Fenestration Product U-factors |
| NFRC 200 |
Procedure for Determining Fenestration Product Solar Heat Gain Coefficient and Visible Transmittance at Normal Incidence |
| ASTM E90 / E413 |
Laboratory Measurement of Airborne Sound Transmission Loss / Classification for Rating Sound Insulation (STC) |
| ASTM E1332 |
Standard Classification for Rating Outdoor-Indoor Sound Attenuation (OITC) |
| IBC Chapter 24 |
International Building Code — Glass and Glazing |
3 Submittals
3.1 Action Submittals
3.1.1The following submittals shall be submitted for review and returned before fabrication begins.
☐ Curtain wall shop drawings (elevations, sections, and details)
☐ Structural calculations signed and sealed by licensed PE
☐ Thermal analysis (AAMA 1503 / AAMA 507) and NFRC ratings
☐ Laboratory test reports (E283, E331, AAMA 501.1, E330)
☐ Seismic drift / thermal cycling test reports (where required)
☐ Structural silicone adhesion and compatibility test results (SSG)
☐ Framing, gasket, sealant, anchor, and finish product data
☐ Finish samples on actual or equivalent extrusion profile
3.1.2Framing, glazing, and structural submittals shall be coordinated into a single review package so that mullion depths, glazing-pocket geometry, IGU thicknesses, anchor preparations, and movement provisions are reconciled against one another before any product is fabricated.
3.1.3Shop drawings shall provide elevations of every curtain wall condition drawn to scale, with the mullion grid, transom lines, floor lines, spandrel locations, glass type designations keyed by lite, and dimensions of all framing members and rough openings.
3.1.4Section and plan details shall be provided at the head, base, jamb, typical vertical mullion, typical horizontal, slab-edge anchor, spandrel, corner, and every transition to an adjacent envelope assembly.
3.1.5Details shall show the thermal break, the glazing-pocket and pressure-plate arrangement, the gasket compression, the structural silicone bite and glue-line where SSG is used, the pressure-equalization and weep provisions, the perimeter sealant joints, the anchor type and adjustment range, and the air- and water-barrier continuity.
3.1.6Wind-load and dead-load calculations for the framing, the glazing retention, and the anchorage shall be signed and sealed by a professional engineer licensed in the project jurisdiction, demonstrating compliance with the design pressures established in the project structural drawings.
3.1.7The structural calculations shall address mullion spans and deflection limits, mullion reinforcing where required, glass load distribution coordinated with Glazing (ASTM E1300), anchor capacity at every condition, and the accommodation of thermal movement and seismic interstory drift. 3.1.8Where structural silicone glazing is used, the calculations shall size the structural bite and glue-line thickness for both the wind load and the glass dead-load weight.
3.1.9Thermal transmittance (U-factor) and condensation resistance results per AAMA 1503, or a thermal simulation per AAMA 507, shall be submitted for the framing and for the complete fenestration product.
3.1.10Whole-product NFRC 100 U-factor and NFRC 200 SHGC and VLT shall be submitted where the energy code requires certified ratings.
3.1.11Laboratory test reports for the curtain wall system shall document air infiltration per ASTM E283, static water penetration per ASTM E331, dynamic water penetration per AAMA 501.1, and structural performance per ASTM E330.
3.1.12Where required, seismic interstory drift per AAMA 501.4 and thermal cycling per AAMA 501.5 test reports shall be submitted.
3.1.13Where structural silicone glazing is used, the structural sealant manufacturer's adhesion and compatibility test results (per ASTM C1135 and the manufacturer's protocol) shall be submitted for the specific glass coating, the specific framing finish, the setting blocks and spacer materials, and any backer or substrate the structural sealant will contact.
3.1.14The structural sealant shall conform to ASTM C1184 and the design shall comply with ASTM C1401.
3.1.15Manufacturer's published product data shall be submitted for the framing system, gaskets, sealants, thermal-break material, anchors, and finish, including the system's tested performance ratings.
3.1.16Samples of each finish, minimum 12 in. by 12 in., shall be submitted on the actual extrusion profile or on a representative profile of equivalent thickness, demonstrating color, gloss, and finish quality.
3.1.17For anodized finishes the samples shall demonstrate the lot-to-lot color range so that color variation across the facade can be evaluated.
3.2 Closeout Submittals
3.2.1At substantial completion the Contractor shall provide the following closeout submittals before final acceptance:
- As-built elevations reflecting any field changes to the mullion grid, glass types, or anchorage
- Field test reports per AAMA 503 (chamber) or AAMA 501.2 (diagnostic hose) and ASTM E1105 where field water testing was performed
- Mockup test reports, including any deficiencies identified and the corrective actions taken before production release
- Cleaning and maintenance instructions for the framing finish, glass, gaskets, and sealants, including approved cleaning products and products that shall not be used on the finish
- Warranty documentation from the curtain wall manufacturer, the structural silicone sealant manufacturer (SSG), the IGU manufacturer, and the finish applicator
☐ As-built elevations
☐ Field test reports (AAMA 503 / AAMA 501.2 / ASTM E1105)
☐ Mockup test reports and corrective-action record
☐ Cleaning and maintenance instructions
☐ Curtain wall system warranty (minimum 2 years)
☐ Finish warranty (20 years for AAMA 2605)
☐ Structural silicone glazing warranty (SSG)
☐ IGU warranty (minimum 10 years against seal failure)
4 Quality Assurance
4.1 Manufacturer and Fabricator Qualifications
4.1.1The curtain wall manufacturer shall demonstrate a minimum of ten years of continuous production of aluminum curtain wall systems of the type and performance specified.
4.1.2The curtain wall manufacturer shall provide independent laboratory test reports for the specific system demonstrating compliance with the air, water, and structural performance required by this standard and the drawings.
4.1.3The fabricator and erector shall demonstrate a minimum of five years of experience with curtain wall of comparable scope, height, and complexity.
4.2 Structural Silicone Quality Program
4.2.1Where structural silicone glazing is used, the glazier shall be trained and approved by the structural silicone sealant manufacturer for the specific system.
4.2.2The structural sealant manufacturer shall review the structural joint design, confirm substrate compatibility and adhesion before production, and provide on-site instruction at the start of glazing.
4.2.3SSG glazing shall be performed in a controlled shop environment wherever practicable.
4.2.4Field-applied structural silicone shall be used only where the system design requires it and only under the manufacturer's field quality program.
4.2.5A documented quality-control program shall record, for each production run, the sealant lot, mixing (for two-part), cure verification, bead dimension, and the daily adhesion (snap/peel) tests.
NOTE In a structurally glazed wall the silicone is the load path that holds the glass on the building — there is no mechanical capture on the structural edges — so an undetected adhesion or cure failure is a glass-fallout hazard, not merely a leak. Adhesion and compatibility are verified before and during production precisely because they cannot be inspected after the fact in a cured, glazed unit. (4.2.6)
4.3 Mockup
NOTE A laboratory performance mockup of representative bays is the standard verification for curtain wall and is the appropriate default for any project of consequential height or area. (4.3.1)
Visual mockup — color, finish, and glass type confirmation only
Laboratory mockup — performance chamber test (E283, E331, AAMA 501.1, E330)
Laboratory mockup plus AAMA 501.4 interstory drift and AAMA 501.5 thermal cycling
Field mockup — typical bays installed in place and field tested (AAMA 503 / ASTM E1105)
Laboratory performance mockup plus field mockup (both)
4.3.2The laboratory performance mockup shall include a typical vision area, a spandrel, a horizontal and vertical mullion intersection, a corner or movement joint, an anchor condition, and the transition to an adjacent assembly.
4.3.3The mockup shall be tested as a complete system so the air barrier, water management, anchorage, and movement provisions are evaluated together.
4.3.4Deficiencies found in the mockup shall be corrected and re-tested before production fabrication is released.
4.3.5A visual-only mockup confirms appearance but does not verify performance and shall be used only where a separate, tested system of record establishes the performance.
4.4 Professional Engineer of Record for the Curtain Wall
4.4.1The framing, glazing retention, and anchorage shall be designed by, and the structural calculations signed and sealed by, a professional engineer licensed in the project jurisdiction.
NOTE The curtain wall is a delegated-design (deferred-submittal) system in most jurisdictions: the contract drawings establish the performance criteria, geometry, and design pressures, and the specialty engineer engaged by the curtain wall contractor completes the member sizing, connection design, and anchorage within those criteria. (4.4.2)
20150
20304050607590110130150
Default: 50 psf
30200
30456080100130160200
Default: 75 psf
5.1.1The curtain wall design positive and negative wind pressures shall be derived from the project structural drawings and the building-code wind determination for the project location, height, exposure category, and the zone (field, edge, or corner) in which each portion of the wall falls.
5.1.2Corner and parapet zones carry substantially higher local pressures than the wall field; the system, the glass, and the anchors in those zones shall be designed for the higher local pressure rather than the field pressure.
NOTE Selection of the performance tier follows building height and exposure: low- and mid-rise walls in sheltered exposures carry modest pressures, while high-rise walls and exposed or coastal sites routinely require design pressures well above the storefront range, which is the principal reason curtain wall framing is deeper and more heavily reinforced than storefront framing. (5.1.3)
○ L/175 or 3/4 in., whichever is smaller (standard)
○ L/240 or 3/4 in., whichever is smaller (stricter, large lites or stone/panel infill)
○ Per project structural specifications
○ L/360 or 1/8 in., whichever is smaller (standard, protects glass edge engagement)
○ Per glazing manufacturer's published limit for the lite size
5.2.1The framing shall withstand the design positive and negative wind pressures without permanent deformation, glass breakage, anchor failure, or loss of air or water seal, verified per ASTM E330.
5.2.2A proof load test at 1.5 times the design pressure shall produce no permanent deformation in any framing member exceeding 0.2 percent of its span.
5.2.3Framing deflection normal to the wall under the design wind load shall not exceed L/175 of the clear span, or 3/4 in., whichever is smaller.
5.2.4Deflection of a member carrying glass shall additionally be limited so that the glass edge engagement (bite) is not lost and the glazing pocket does not open.
NOTE Excessive mullion deflection is a direct cause of glazing-pocket leakage and gasket disengagement. (5.2.5)
5.3 Air Infiltration
0.010.06
0.010.030.040.06
Default: 0.06 cfm/sf
5.3.1Air infiltration through the fixed curtain wall shall be tested per ASTM E283 at a static pressure differential of 6.24 psf (equivalent to a 50 mph wind) and shall not exceed 0.06 cfm per square foot of wall area.
NOTE Air leakage is controlled at a continuous interior air-seal plane — the gaskets, the inner glazing seal, and the framing joinery — which is why the air barrier of the wall is detailed at the interior, not the exterior. A leaky air seal not only wastes energy but drives interior-air moisture into the framing cavities, where it condenses against the cold exterior aluminum and emerges as apparent "leakage." (5.3.2)
5.4 Water Penetration
6.2420
6.24810121520
Default: 12 psf
○ Required at the same pressure as the static test (standard for curtain wall)
○ Not required (low-rise, sheltered exposure only)
5.4.1Water penetration shall be tested by both static and dynamic methods.
5.4.2The static test per ASTM E331 shall be performed at a pressure equal to a defined fraction of the design wind pressure, typically 20 percent, with a minimum test pressure of 6.24 psf and a typical practical maximum near 20 psf.
5.4.3The dynamic test per AAMA 501.1 shall apply the same water rate while a propeller or aircraft-engine-driven air stream produces the test pressure dynamically, which more realistically reproduces the gusting, turbulent pressures a real wall sees.
5.4.4No uncontrolled water shall pass beyond the interior face during either test.
5.4.5Water that enters the glazing pocket or framing cavities shall drain back to the exterior through the weep and pressure-equalization system and shall not be visible on the interior.
5.5 Thermal Transmittance, Solar Gain, and Condensation Resistance
0.240.65
0.240.280.320.380.420.50.550.65
Default: 0.42 Btu/h·sf·°F
0.180.5
0.180.220.250.30.350.40.5
Default: 0.28 SHGC (unitless)
4580
45556065707580
Default: 65 CRF
5.5.1The complete fenestration product shall meet the U-factor, SHGC, and VLT required by the energy-compliance documentation.
5.5.2The framing thermal transmittance and condensation resistance shall be determined by test per AAMA 1503 or by simulation per AAMA 507.
5.5.3Whole-product U-factor and SHGC shall be certified per NFRC 100 and NFRC 200 where the energy code requires certified ratings.
5.5.4A continuous thermal break in the framing shall be provided.
NOTE A continuous thermal break is essential because bare aluminum is a powerful thermal bridge, and an un-broken mullion both wastes energy and drops the interior framing surface below the indoor dew point, producing condensation that streaks the glass, stains finishes, and over time corrodes and grows mold. The thermal break interrupts the metal-to-metal path so the interior surface stays warm enough to resist condensation at the project's design interior humidity. (5.5.5)
NOTE A CRF below approximately 55 indicates a high risk of interior condensation on the framing edges in cold climates; CRF of 65 or higher is appropriate for most heated commercial applications in climate zones 5 through 7. (5.5.6)
5.5.7Buildings with elevated interior humidity (natatoriums, hospitals, food processing) shall require CRF of 70 or higher and shall be reviewed against the project's interior dew point with the curtain wall manufacturer.
Not required — no acoustic specification
STC 35–38 (moderate urban noise control)
STC 39–45 (transit-adjacent, healthcare, hospitality)
OITC 30–35 (aircraft / heavy traffic exterior noise)
OITC 36 and above (severe exterior noise exposure)
5.6.1Where the contract documents require acoustic performance, the assembly shall meet the specified Sound Transmission Class (STC, per ASTM E90 / E413) or, for exterior environmental noise such as aircraft and traffic, the Outdoor-Indoor Transmission Class (OITC, per ASTM E1332).
5.6.2The framing seals and any spandrel back-up shall not short-circuit the rated glass.
5.7 Seismic Interstory Drift and Thermal Movement
Not applicable — low seismic, drift not governing
Standard — AAMA 501.4 static drift test to design drift
Enhanced — AAMA 501.4 plus AAMA 501.6 dynamic glass-fallout test (high seismic)
0.253
0.250.50.7511.523
Default: 0.75 in
5.7.1The curtain wall shall accommodate the design seismic interstory drift and the design thermal movement without glass breakage, glass fallout, or loss of the perimeter seal.
5.7.2The framing, the glazing pocket clearances, and the anchors shall be detailed to absorb the imposed drift — through glass-to-frame clearance, sliding/rocking glazing pockets, or articulated splice joints — rather than transmitting it into the glass.
5.7.3Drift accommodation shall be verified per AAMA 501.4 (static) and, where glass fallout is a design concern, per AAMA 501.6 (dynamic).
5.7.4Thermal movement shall be accommodated at horizontal stack joints and at anchor slots sized for the calculated expansion and contraction of the aluminum across the project temperature range.
NOTE Because the wall is anchored to the structure at each floor and spans the slab edge, the relative horizontal movement of one floor with respect to the next is imposed directly on the wall. (5.7.5)
5.8 Impact and Wind-Borne Debris Resistance
Not required — project is not in a wind-borne debris region
Required — ASTM E1996 small missile (elevations above 30 ft)
Required — ASTM E1996 large missile (within 30 ft of grade)
Required — large missile plus enhanced design pressure (coastal high-velocity zones)
5.8.1For projects in hurricane wind-borne debris regions, the curtain wall and its glazing shall be tested per ASTM E1886 and shall comply with ASTM E1996 for the applicable wind zone and missile category.
5.8.2Impact-rated assemblies require laminated glass (coordinated under Glazing), a framing system and glazing retention proven to hold the laminated lite in the frame through the cyclic pressure following impact, and structural perimeter anchorage. 5.8.3Impact ratings apply to the tested assembly as a whole and shall not be transferred between systems or glass types without an updated test report.
6 System Type and Configuration
6.1 Stick-Built vs. Unitized
NOTE The fundamental system decision is whether the wall is assembled piece-by-piece in the field (stick-built) or shop-assembled into pre-glazed panels that are hung on the building as units (unitized). (6.1.1)
○ Stick-built — field-assembled and field-glazed (low/mid-rise, irregular geometry)
○ Unitized — shop-assembled, pre-glazed panels interlocked in the field (high-rise, large area)
○ Hybrid — unitized typical with stick-built infill at special conditions
NOTE Stick-built systems ship as loose extrusions, anchors, and glass and are erected and glazed in place; they have a lower material cost and more field adjustability and are well suited to low- and mid-rise work and irregular geometry, but they put glazing, sealing, and quality control in the field — at height, exposed to weather, and harder to inspect. (6.1.2)
NOTE Unitized systems are fabricated, glazed, and sealed (including structural silicone, where used) in the controlled shop environment, then craned into place and interlocked at split mullions and stack joints; they cost more per square foot and require crane access and tight dimensional control, but they erect far faster, achieve more consistent water and air performance, and remove the structural glazing from the field. Unitized construction is the predominant choice for high-rise and large-area facades for these reasons. (6.1.3)
6.2 Glazing Method — Captured vs. Structural Silicone
6.2.1The glass may be retained mechanically (captured) or by structural silicone (SSG).
Captured — four-side mechanical (pressure plate and cover, gasketed) (standard)
Two-side structural silicone (captured horizontals, structural verticals, or inverse)
Four-side structural silicone (all edges bonded, flush mullion-free exterior)
NOTE In a captured (mechanically glazed) system the glass is held on all four edges by a continuous exterior pressure plate and a snap-on cover, compressing gaskets against both faces; this is the most robust and inspectable retention and is the appropriate default. (6.2.2)
NOTE In structural silicone glazing the structural silicone bonds the glass to the framing and carries the wind load into the frame without a mechanical capture on the structural edges — two-side SSG captures the horizontals and structurally bonds the verticals (or vice versa), and four-side SSG bonds all four edges for a fully flush, mullion-free exterior appearance. (6.2.3)
NOTE SSG is selected for its appearance and for the slightly better thermal and water performance of an uninterrupted exterior, but it transfers the entire load path to the sealant; this is why ASTM C1184 sealant conformance, ASTM C1401 design, factory application, and the adhesion/compatibility program above are mandatory for SSG and why field-applied four-side SSG is generally avoided. (6.2.4)
6.3 Water Management — Pressure-Equalized vs. Face-Sealed
NOTE A curtain wall manages water by one of two principles. (6.3.1)
○ Pressure-equalized rain screen — vented/weeped cavity, internal drainage (standard)
○ Face-sealed (barrier) — single exterior seal (low-rise, sheltered exposure only)
NOTE A face-sealed (barrier) wall relies on a single continuous exterior seal to stop all water at the outer face; it is simpler but unforgiving, because any breach in that single line lets water in with no second line of defense. (6.3.2)
NOTE A pressure-equalized rain-screen wall, the modern standard described in AAMA CW-RS-1, accepts that some water will pass the outer screen and instead defeats the forces that drive water inward. The glazing pocket and internal cavities are vented to the exterior so the air pressure inside the cavity equalizes with the wind pressure outside; with no pressure difference across the outer screen, the dominant force pushing water through joints is removed, and the small amount of water that does enter is collected on internal gutters and drained back out through weeps. The interior line is then sealed for air, and the exterior screen sheds the bulk of the water — two lines of defense instead of one. (6.3.3)
6.3.4Pressure-equalized rain-screen design shall be the appropriate default for curtain wall; face-sealed design shall be limited to low-exposure conditions.
6.4 Mullion Sightline and Depth
2 in (51 mm) — minimal sightline, light to moderate loads
2-1/2 in (64 mm) — standard commercial sightline (typical)
3 in (76 mm) — wider sightline, larger lites or higher loads
312
34567.5910.512
Default: 6 in
○ Not required — aluminum mullion adequate for span and pressure
○ Steel tube reinforcement inside mullion cavity for span/pressure
○ Deeper mullion in lieu of reinforcing
NOTE The mullion face width (sightline) is an architectural decision; the mullion depth is a structural one, driven by the span between anchors and the design wind pressure. (6.4.1)
6.4.2Deeper mullions and supplemental steel reinforcing shall be used to resist higher loads and longer spans.
6.4.3The mullion depth shall be confirmed against the manufacturer's span tables and the signed structural calculations for the actual span and pressure, including the higher corner-zone pressure where applicable.
7 Framing and Materials
7.1 Aluminum Extrusions
○ 6063-T6 structural framing; 6063-T5 trim and covers (as required by member function)
○ 6063-T6 throughout
7.1.1Framing extrusions — mullions, transoms, pressure plates, covers, and trim — shall conform to ASTM B221, alloy 6063 in temper T5 or T6 as appropriate to the structural and finishing requirements of each profile.
7.1.2Temper T6 shall be used for structural mullions and transoms; temper T5 is acceptable for non-structural pressure plates, covers, and trim.
7.1.3The minimum wall thickness of primary structural members shall be 0.090 in. (2.3 mm); non-structural trim shall be not less than 0.062 in. (1.6 mm).
7.1.4Members shall be of adequate section to meet the deflection limits above without relying on the glass for stiffness.
7.2 Thermal Break
Polyamide strut (glass-reinforced nylon, mechanically crimped) — higher performance
Poured-and-debridged polyurethane — moderate performance
7.2.1Framing members shall be thermally broken with a continuous thermal barrier between the interior and exterior aluminum.
7.2.2A polyamide strut (pultruded glass-fiber-reinforced nylon mechanically crimped into the profiles) or a poured-and-debridged polyurethane barrier may be used.
7.2.3The thermal-break dimension shall be selected to meet the project U-factor and CRF targets.
NOTE Polyamide struts provide higher thermal performance, greater structural shear transfer between the inner and outer aluminum, and reliable dual-color (different interior and exterior) finishing, while poured-and-debridged is acceptable for moderate-performance walls. (7.2.4)
7.3 Steel Reinforcing and Fasteners
7.3.1Steel reinforcing inserted within mullion cavities shall be hot-dip galvanized or otherwise corrosion-protected and shall be isolated from the aluminum to prevent galvanic corrosion.
7.3.2Exposed and concealed fasteners and anchors shall be stainless steel or another corrosion-resistant material compatible with both the aluminum and the embedded or structural steel they connect to.
7.3.3Dissimilar metals in contact shall be separated by a non-conductive isolator or coating.
7.4 Gaskets
7.4.1Glazing gaskets shall be extruded EPDM, silicone, or thermoplastic of the durometer and profile specified by the framing system, providing continuous compression against both glass faces at captured edges.
7.4.2Gaskets shall be installed in continuous lengths with splices located and sealed at corners per the manufacturer's instructions.
NOTE A discontinuity at a gasket corner is a common, avoidable leak path. (7.4.3)
8 Glazing Infill
NOTE The glass and insulating glass units are governed by
Glazing, which establishes glass type, heat treatment, load resistance per ASTM E1300, coatings and coating surface, laminated makeups, spandrel frit, IGU certification per ASTM E2190, and the safety-glazing requirements of IBC Chapter 24.
(8.1) NOTE This standard does not duplicate the glazing requirements; it establishes only how the glass is retained, supported, sealed, and drained within the curtain wall framing, and the coordination obligations between the two scopes. (8.2)
8.4 Glass-to-Framing Coordination
8.4.1The IGU overall thickness, edge bite, edge clearance, and weight shall be coordinated between the glazing scope (Glazing) and the framing system so that the glazing pocket, setting blocks, and structural-silicone bite (where SSG is used) suit the actual unit. 8.4.2The IGU secondary seal and any coating that a structural silicone bead will contact shall be confirmed compatible with that silicone under the adhesion/compatibility program.
NOTE An incompatible secondary seal or coating defeats the structural bond and the IGU seal alike. (8.4.3)
8.5 Spandrel Areas
Fritted/opacified spandrel glass with insulated back-pan (typical)
Shadow-box spandrel (clear or coated glass over a finished back-pan with airspace)
Opaque insulated metal infill panel
Not applicable — no spandrel areas
8.5.1Spandrel glass (heat-strengthened with frit or opacifier, per Glazing) or an opaque infill panel shall be set in the same framing with a shadow box or insulated back-pan as detailed. 8.5.2The spandrel cavity shall be detailed for the high heat that builds behind opaque glass and for continuity of the air and thermal control layers with the adjacent vision areas and with Building Thermal Insulation. NOTE At spandrel (non-vision) areas the curtain wall conceals the floor edge, structure, and back-up insulation. (8.5.3)
9 Finishes
Fluoropolymer organic coating, AAMA 2605 (superior, 20-yr class) — exterior default
Fluoropolymer organic coating, AAMA 2604 (high performance)
Anodized, AAMA 611 Architectural Class I (integral color, abrasion resistant)
Anodized, AAMA 611 Architectural Class II (interior or low-exposure)
9.1Exposed aluminum shall receive an anodized or organic-coated finish as scheduled.
9.2Organic (fluoropolymer) coatings to AAMA 2604 provide good color and chalk/fade resistance for typical commercial work.
9.3AAMA 2605 (the highest-performing fluoropolymer class) shall be specified where the longest finish life and the best color and gloss retention are required, which is the appropriate default for tall and prominent facades that cannot easily be refinished.
9.4Anodized finishes to AAMA 611 provide a durable, abrasion-resistant integral-color finish; architectural Class I anodizing (the thicker coating) shall be used for exterior exposure.
10 Anchorage and Movement
10.1 Anchorage to the Building Structure
Slab-edge embedded plate with welded/bolted clip (typical)
Cast-in channel anchor with serrated/adjustable connection
Through-slab or face-of-slab bolted anchor
Spandrel-beam or steel-edge anchor
10.1.2Anchors shall be three-way adjustable (in, out; up, down; and in-and-out of plane) to absorb construction tolerances of the structure without forcing the framing out of plane or out of plumb.
10.1.3The anchor design, the embedment or attachment, and the load path into the structure shall be by the curtain wall engineer and coordinated with the building structural engineer.
10.1.4The anchor shall transfer wind load (in and out) and the curtain wall dead weight (gravity) into the structure, and shall do so while permitting the movements below.
10.2 Movement Accommodation
○ Telescoping stack joint at each floor (unitized) (standard for unitized)
○ Slotted/expansion horizontal mullion (stick-built)
○ Per manufacturer's tested movement detail
10.2.1The framing and anchorage shall accommodate, without distress: the live-load and creep deflection of the supporting floor edges; the differential vertical movement between floors; the thermal expansion and contraction of the aluminum over the project temperature range; and the seismic interstory drift established above.
10.2.2Vertical movement shall be taken at horizontal stack/expansion joints (the telescoping split between a panel and the one below in a unitized wall, or the slotted/expansion horizontal in a stick wall).
10.2.3The dead load of each segment shall bear at a defined point while the joint above is free to move.
10.2.4Anchor slots and shims shall preserve the design movement range after erection.
NOTE An anchor inadvertently welded or bolted solid where it was meant to slide will transfer building movement into the glass and is a defect. (10.2.5)
11 Air and Water Seal Continuity
NOTE The single most common source of curtain wall failure is not the wall itself but the perimeter — the transition where the curtain wall meets the adjacent construction at the head, jamb, base, and at any penetration or interruption. (11.1)
NOTE The wall's own air and water performance is verified by testing, but the perimeter joint is built in the field, at the interface between two trades, and is where the air barrier and water barrier of the curtain wall must be made continuous with the air barrier and water barrier of the surrounding wall. A discontinuity here lets air and water bypass an otherwise sound wall. (11.2)
11.3 Air Barrier Continuity
11.3.1The interior air-seal plane of the curtain wall shall be made continuous with the building air barrier of the adjacent assemblies, coordinated with Air Barriers. 11.3.2The transition membrane or sealant shall bridge from the curtain wall's interior air seal to the adjacent air barrier with a detailed, continuous, and durable connection that accommodates the differential movement between the curtain wall and the adjacent structure.
11.3.3The connection shall be detailed on the shop drawings and verified on the mockup.
11.4 Perimeter Water Seal and Flashing
Silicone — ASTM C920 Type S, Grade NS, Class 50/100 (highest movement, longest life)
Polyurethane — ASTM C920 Type S, Grade NS, Class 35 (paintable, moderate movement)
11.4.1The perimeter water seal shall direct any water that reaches the perimeter back to the exterior.
11.4.4The sealant manufacturer shall confirm compatibility with the curtain wall finish and the adjacent substrate.
12 Fabrication
○ Factory/shop applied and cured under QC program (standard for SSG)
○ Field applied only where system design requires, under manufacturer field QC
12.1Framing shall be fabricated to the dimensions and tolerances of the reviewed shop drawings, with members cut, machined, and prepared for assembly in the shop.
12.2Joints in the framing shall be sealed against air and water as the system design requires.
12.3For unitized systems, the panels shall be assembled, glazed, sealed, and — where structural silicone is used — structurally glazed and cured in the controlled shop environment under the quality program above before shipment.
12.4Structural silicone shall not be loaded until it has reached the cure required by the sealant manufacturer.
12.5Aluminum shall be protected from shop through site per AAMA CW-10.
12.6Finished surfaces shall be protected with a strippable coating or covering, and finished members shall not be stored or handled in a way that abrades or contaminates the finish.
13 Installation
13.1 Anchorage and Erection
13.1.1The Contractor shall install the curtain wall plumb, level, and in plane within the system tolerances, anchored to the structure at the locations and with the adjustment shown on the reviewed shop drawings.
13.1.2Anchors shall be set and adjusted to absorb the as-built tolerances of the structure, then secured so that the design movement range remains free at the movement joints.
13.1.3Welded anchor connections shall be touched up with corrosion-protective coating; dissimilar metals shall be isolated.
13.2 Sequence and Coordination
13.2.1Erection shall be sequenced with the adjacent envelope trades so the air-barrier and water-barrier transitions can be made continuous as the wall goes up, rather than retrofitted behind a completed wall.
13.3 Perimeter Seal to the Air Barrier
13.3.1The perimeter air-barrier transition shall be installed as the wall is erected, continuously connecting the curtain wall's interior air seal to the adjacent air barrier per Air Barriers, and shall be inspected before it is concealed. 13.3.2The perimeter water seal and pan flashing shall be installed so that the curtain wall weep drainage and any perimeter water discharge to the exterior.
13.4 Glazing, Setting Blocks, and Weep System
○ Provided and kept clear at each glazing pocket per system design (standard)
○ Not applicable — face-sealed (barrier) system
13.4.1Field glazing (stick systems) shall be performed only after the framing is installed plumb, level, and weather-protected and the glazing pockets are clean and dry.
13.4.2Each lite shall be set on setting blocks at the quarter points (or as the glazing manufacturer directs for the lite size), centered in the pocket with the required edge clearance, face clearance, and bite per Glazing and the framing manufacturer's glazing instructions. 13.4.3The pressure-equalization and weep openings shall be kept clear and unobstructed by gaskets, setting blocks, or sealant.
NOTE A blocked weep defeats the rain-screen drainage and traps water against the IGU edge seal, which is a leading cause of premature IGU failure. (13.4.4)
14 Field Quality Control
14.1 Field Water Testing
AAMA 503 chamber test with ASTM E1105 (certified field performance)
AAMA 501.2 diagnostic hose check (leak location / quality assurance)
Both — diagnostic 501.2 during construction, 503 for acceptance
Not required
14.1.1Where the contract documents require field water testing of the installed wall, the wall shall be tested per AAMA 503 with ASTM E1105 (calibrated chamber) at a pressure equal to two-thirds of the laboratory test pressure, or checked diagnostically per AAMA 501.2 (calibrated spray nozzle, no chamber) to locate leaks.
14.1.2Leakage found in field testing shall be located, corrected, and re-tested.
NOTE The diagnostic AAMA 501.2 hose check is valuable for finding the location of a leak during construction but does not substitute for AAMA 503 chamber testing where certified field performance is required. (14.1.3)
14.2 Mockup Verification
14.2.1Where a mockup is required, the field or laboratory mockup shall be tested and accepted before production release as established under Quality Assurance.
14.2.2The installed wall shall match the accepted mockup in materials, details, and workmanship.
15 Cleaning and Protection
Approved non-abrasive cleaners only — no abrasives, scrapers, or acids/alkalis
Per finish and glass manufacturers' written cleaning procedures
15.1Finished aluminum and glass shall be protected from damage and from construction contaminants from delivery through substantial completion, consistent with AAMA CW-10.
15.2Welding, cutting, and grinding shall not be performed near installed glass or finished aluminum without sacrificial protection.
NOTE Weld spatter and grinding sparks permanently damage glass and finishes. (15.3)
15.4At substantial completion the aluminum and glass shall be cleaned with non-abrasive cleaners approved by the finish and glass manufacturers.
15.5Abrasive pads, scrapers, and acidic or alkaline construction-residue cleaners shall not contact the finish, the glass coatings, or the IGU edge seals.
16 Warranty
520
51020
Default: 20 years
1015
1015
Default: 10 years
16.1The Contractor shall warrant the curtain wall system against defects in materials and workmanship, including air and water infiltration in excess of the specified performance, for a period of not less than two years from substantial completion.
16.2The finish warranty shall be a minimum of twenty years for AAMA 2605 fluoropolymer coatings (or the published term for the scheduled finish) against color fade, chalk, and film integrity.
16.3The structural silicone glazing warranty (for SSG systems) shall cover adhesive and cohesive failure of the structural sealant for the sealant manufacturer's published term.
16.4The insulating glass unit warranty (coordinated under Glazing) shall be a minimum of ten years against seal failure. 16.5Warranties shall be written in the name of the Owner and shall be transferable for the warranty term.