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Specifying or sourcing architectural aluminum window and door systems requires navigating a dense vocabulary of alloy designations, profile geometries, thermal performance metrics, and third-party certification standards. This glossary consolidates the most important terms — arranged by category — that buyers, architects, and project managers encounter when evaluating aluminum fenestration systems. Whether you are comparing profile depths, interpreting NFRC U-factor labels, or deciding between a 6063-T5 and 6063-T6 extrusion, the definitions below provide the technical grounding you need.

Part I: Alloy and Material Standards

Alloy 6063

The dominant alloy for architectural aluminum extrusions. Alloy 6063 is a magnesium-silicon (Mg–Si) series aluminum, valued for its excellent extrudability, smooth surface finish, and good corrosion resistance. Per the Aluminum Extruders Council (AEC), 6063 can be extruded into thin-walled, complex cross-sections that would be impractical with higher-strength alloys, making it the first choice for window frames, curtain wall mullions, and door profiles. Minimum tensile strength is typically 150 MPa in the annealed state, rising to 205–240 MPa in T5/T6 tempers.

Temper Designations: T5 vs. T6

The letter-number suffix after the alloy number describes the thermal treatment applied after extrusion.

• T5 (Artificially Aged): The profile is cooled from the extrusion die and then artificially aged in an oven at approximately 175–180 °C. This is the most common temper for 6063 architectural profiles. Typical yield strength: 145–165 MPa.
• T6 (Solution Heat-Treated + Artificially Aged): The billet is first solution-heat-treated above 500 °C, quenched, then artificially aged. T6 yields 15–25% higher strength than T5, at the cost of slightly more distortion risk during quenching. Typical yield strength: 215 MPa for 6063-T6. Specified when profiles must carry elevated structural loads, such as large-span curtain wall mullions or heavy sliding door tracks.

Alloy Comparison: 6063, 6061, and 6005

While 6063 dominates residential and commercial fenestration, specifiers sometimes encounter alternative alloys for structural or industrial applications. The table below summarizes key distinctions, based on data from American Douglas Metals:

For nearly all window and door profiles, 6063-T5 provides sufficient structural performance while delivering the surface quality required for powder coating and anodizing. Specifying T6 is justified for profiles exceeding 2.4 m spans or carrying significant in-plane loads.

Part II: Profile Geometry and System Depth

Profile Depth

Profile depth — sometimes called frame depth or installation depth — refers to the front-to-back dimension of the aluminum extrusion as measured perpendicular to the glass plane. This single parameter has an outsized effect on thermal performance, glazing capacity, and structural rigidity. Industry practice groups profiles into the following depth classes, as documented by ServiceLink SA and corroborated by systems data from Schüco and Reynaers:

• 50 mm: Standard residential, non-thermal-break profile. Adequate for single or basic double glazing in temperate climates. Frame U-value (Uf) typically 5.5–6.5 W/m²K.
• 60–65 mm: Entry-level thermal break series. Accommodates double-glazed units up to 28 mm. Uf typically 1.7–2.2 W/m²K with PA66 thermal break strip. Example: Schüco AWS 60 (Uf ≥ 1.7 W/m²K, max glass 50 mm).
• 70–75 mm: Mid-range high-performance series. Accepts double or triple glazing. Uf typically 1.2–1.8 W/m²K. Industry benchmark: Schüco AWS 70 HI (Uf ≥ 1.2 W/m²K, whole-window Uw from 0.71 W/m²K with optimal glazing); Reynaers CS 77 (Uf ≥ 1.47 W/m²K).
• 80–95 mm: Super-insulated commercial series. Supports triple glazing up to 68 mm, passive house certification. Uf down to 0.77–1.0 W/m²K. Example: Schüco AWS 90 SI+ (Uw ≤ 0.77 W/m²K with optimal glazing).

Thermal Break (Polyamide Strip)

A thermal break is a low-conductivity barrier — most commonly a glass-fiber-reinforced polyamide 66 (PA66-GF25) strip — mechanically locked between the exterior and interior aluminum sections of a profile. Without a thermal break, aluminum's high thermal conductivity (≈ 160 W/m·K) creates a direct heat-transfer path through the frame, dramatically increasing frame U-value and promoting condensation. The width of the PA66 strip correlates directly with thermal performance: 24 mm strips yield Uf ≈ 1.8–2.2 W/m²K; 32–35 mm strips achieve Uf ≈ 0.8–1.1 W/m²K, as shown in the depth comparison table above (SGL Doors & Windows).

Multi-Chamber Profile Design

Modern thermal break profiles incorporate multiple hollow chambers within the extruded cross-section. Each chamber creates a dead-air space that resists heat conduction and convection. Commercial-grade profiles typically feature three to four chambers; passive-house-grade systems may use five or more, combined with foam-filled insulating bars between the PA66 strips.

Face Width (Sight Line)

The visible width of the frame or sash member as seen from the interior or exterior. Narrower face widths maximize glazed area and produce a more contemporary aesthetic. Premium concealed-vent systems from Reynaers (CS 77 Hidden Vent: 17.5 mm visible) and Schüco (AvanTec hardware) achieve face widths below 20 mm by hiding the sash behind the outer frame when closed.

Part III: Window Typology by Profile Series

Casement Window Profiles

Casement windows are side-hung, opening outward (or inward in European tilt-and-turn applications) on vertical hinges. Profile systems for casement windows must accommodate concealed multi-point locking mechanisms and, in larger sashes, handle loads up to 160 kg. Minimum recommended profile depth for double-glazed casements is 60 mm; high-security commercial casements commonly use 70–75 mm series profiles with RC2-rated hardware.

Awning Window Profiles

Awning windows are top-hinged and open outward at the bottom. Because the sash hangs from scissor or friction hinges at the top, the profile design must handle concentrated load at the head. Awning profiles typically share the same depth range as casements (60–70 mm) and are frequently mulled with fixed lites in commercial façades to provide ventilation without compromising the envelope plane.

Fixed (Picture) Window Profiles

Fixed profiles carry no hardware and are simpler in cross-section than operable profiles, but they must still provide adequate bead depth and rebate height to retain the glazing unit under wind and thermal loads. Fixed profiles within curtain wall and window wall systems are typically the same nominal depth as the operable units they adjoin, ensuring a flush plane across the façade.

Tilt-and-Turn Window Profiles

Tilt-and-turn (or tilt-turn) windows offer dual operating modes: tilting inward from the top for secure ventilation, or turning inward from the side for cleaning and egress. The hardware mechanism is complex and requires additional sash depth to house the multi-point espagnolette locking system. Most dedicated tilt-turn profile series range from 60 mm to 77 mm depth; Reynaers CS 77 is a well-known European example that accommodates glass up to 52 mm in tilt-turn configuration. Per Piva Windows, advanced systems (e.g., Metropolitan76) achieve Uf ≈ 1.1 W/m²K with three-seal perimeter gaskets.

Sliding Window and Sliding Door Profiles

Sliding systems require dedicated track and sill profiles with low-friction rollers or glide bearings. Because sashes must travel within a continuous sill extrusion, the frame depth for sliding systems is measured differently — the sill depth may be 80–120 mm to house double-track configurations. Thermal performance of sliding systems is generally lower than equivalent-depth tilt-turn or casement profiles because compression seals cannot be used along the sliding edges; brush pile or fin-seal weatherstripping is substituted, with an inherently higher air infiltration rate.

Part IV: Performance Ratings and Certification Terms

U-Factor (Thermal Transmittance)

U-factor (or U-value) quantifies the rate of non-solar heat flow through an assembly, expressed in W/m²K (SI) or BTU/hr·ft²·°F (imperial). Lower values indicate better thermal insulation. For windows, three distinct U-values are reported:

• Uf (Frame U-value): Heat loss through the frame profile only.
• Ug (Glazing U-value): Heat loss through the glass unit only (center-of-glass).
• Uw (Whole Window U-value): Area-weighted combination of frame, glass, and edge seal, per EN ISO 10077-1 (Europe) or NFRC 100 (North America).

The U.S. Department of Energy notes that NFRC-rated U-factors are determined for the whole window assembly, making direct comparisons between products straightforward. ENERGY STAR qualification thresholds by U.S. climate zone range from Uw ≤ 0.30 (Northern) to ≤ 0.40 (North-Central) to ≤ 0.60 (South-Central) BTU/hr·ft²·°F.

NFRC (National Fenestration Rating Council)

The NFRC is a nonprofit organization that administers the North American voluntary certification and labeling program for windows, doors, and skylights. NFRC labels report U-factor, Solar Heat Gain Coefficient (SHGC), Visible Transmittance (VT), Air Leakage (AL), and Condensation Resistance (CR). NFRC 100 is the test protocol for whole-window U-factor, using both physical testing and THERM/WINDOW computer simulation. NFRC certification is the only thermal rating system currently referenced in U.S. model energy codes (ASHRAE 90.1, IECC), per Graham Architectural Products.

AAMA (American Architectural Manufacturers Association)

AAMA (now operating under the Fenestration & Glazing Industry Alliance, FGIA) publishes the most widely referenced North American standards for aluminum window and door performance, including:

• AAMA 1503: Thermal transmittance and condensation resistance factor (CRF) for windows and doors — physical test method.
• AAMA 507: Thermal performance rating for storefront, curtain wall, and window wall systems (commercial applications).
• AAMA 2604 / 2605: Performance specifications for high-performance organic coatings (powder coat and PVDF) on architectural aluminum — 5-year and 10-year weatherability grades, respectively.
• AAMA 611: Voluntary specification for anodized architectural aluminum.

SHGC (Solar Heat Gain Coefficient)

SHGC measures the fraction of incident solar radiation admitted through a window — including directly transmitted and absorbed-then-released heat — on a scale of 0 to 1. A lower SHGC reduces cooling loads in hot climates; a higher SHGC is beneficial in cold climates where passive solar gain is desirable. Per the NFRC Consumer Guide to Windows, the typical SHGC range for rated products is 0.00–1.00.

CR / CRF (Condensation Resistance)

Condensation Resistance (CR) under NFRC 500 and Condensation Resistance Factor (CRF) under AAMA 1503 measure a window's ability to resist interior condensation on cold surfaces. Higher values are better. Thermal break profiles dramatically improve CR by eliminating the cold interior aluminum surface that would otherwise form on a non-broken frame in cold weather.

Air Leakage (AL)

Air leakage is the rate of air infiltration through the operable sash/frame interface, measured in cfm/ft² (NFRC) or m³/h·m² (EN standard). AAMA performance classes for prime windows: A1 (≤ 0.37 cfm/ft²), A2 (≤ 0.30), A3 (≤ 0.10). European EN 12207 rates windows from Class 1 (low-rise exposure) to Class 4 (high-rise/severe exposure). Premium tilt-turn and casement profiles with compression perimeter seals routinely achieve Class 3–4.

Part V: Industry Profile System Naming Conventions

The major European and North American aluminum systems manufacturers use a consistent naming logic: the series number indicates the nominal profile depth in millimeters. Buyers should verify this depth refers to the frame profile, not the sash depth, as some manufacturers report sash depth. Key reference systems include:

• Schüco AWS 60 / AWS 60.HI / AWS 70 HI / AWS 90 SI+: German benchmark series. "HI" denotes "High Insulation" with foam-filled insulating bars; "SI+" targets passive house performance (Arkay Windows – Schüco Overview).
• Reynaers CS 60 / CS 68 / CS 77 / CS 86-HI: Belgian-German system with clear performance progression. CS 77 is a three-chamber system with Uf ≥ 1.47 W/m²K; CS 86-HI achieves Uf down to 1.47 W/m²K with triple glazing capability. CS series supports Hidden Vent and Softline design variants.
• YKK AP (North America): Japanese-owned fabricator with products certified to AAMA and NFRC; product lines include the YOW (Outward Opening Window) series for commercial and institutional applications.

Part VI: Surface Finish Terminology

Anodizing

An electrochemical process that grows a dense aluminum oxide layer on the profile surface, typically 10–25 μm thick for architectural grades (AAMA 611 Class I: ≥ 18 μm; Class II: ≥ 10 μm). Anodizing provides superior abrasion resistance and is the preferred finish for high-traffic commercial applications. Color range is limited (clear, bronze, champagne, black, dark bronze).

Powder Coating

Electrostatic application of thermosetting polymer powder, cured at ≈ 200 °C to form a continuous coating typically 60–80 μm thick. AAMA 2604 specifies a 5-year weatherability standard; AAMA 2605 (PVDF/Kynar-based coatings) specifies a 10-year standard with ≥ 50% gloss retention and ≤ 5 ΔE color shift. Powder coating provides an essentially unlimited color palette and is standard on most aluminum window profiles.

Mill Finish

The as-extruded surface condition, without any anodizing or coating. Not suitable for exposed architectural applications. Mill finish profiles are used in concealed structural elements or as a pre-treatment substrate before further finishing.

Part VII: Glazing Interface Terms

Glazing Rebate / Bead

The recessed channel within the profile into which the glass unit is seated. Rebate depth must exceed the glass unit thickness to provide adequate bite (typically 18–25 mm minimum bite). The glazing bead is the removable strip that clamps the glass in place from the interior.

Warm Edge Spacer

The spacer bar separating the glass panes in an insulating glazing unit (IGU) affects the edge-of-glass temperature and condensation risk. "Warm edge" spacers fabricated from stainless steel, foam, or thermoplastic materials replace traditional aluminum spacers, improving the overall Uw by 0.1–0.2 W/m²K and raising the CR rating. Warm edge spacers are standard in modern 70 mm+ profile systems.

Argon / Krypton Fill

Noble gas fills replacing air in the IGU cavity reduce conductive and convective heat transfer. Argon (thermal conductivity ≈ 0.016 W/m·K vs. air at 0.024 W/m·K) is the industry standard fill for double-glazed units at a nominal 90% purity. Krypton (≈ 0.009 W/m·K) is used in triple-glazed units with narrower cavities (6–8 mm) where argon would provide diminishing returns.

Next Steps for Your Project

Selecting the right aluminum profile system for a commercial or residential project begins with matching profile depth and alloy temper to the structural span and climate zone requirements, then confirming thermal performance through NFRC-certified Uw values and AAMA-rated air and water infiltration classes. Working with a knowledgeable supplier who can provide verified test data — not just nominal series specifications — is essential for projects governed by ASHRAE 90.1 or local energy codes.

To explore our full range of architectural aluminum windows and doors — including casement, tilt-turn, sliding, and fixed systems across the 60–90 mm profile depth range — browse our complete product collection. For specification support, project quotes, or technical consultation, contact our team today.