OS2 40 is the iron window in precious metals, with tubular profiles of 12 mm, central node between the two sashes of only 62 mm, depth of 42 mm for glass up to 15 mm. 

Designed for interior design, the light but robust tubular profiles of 0S2 40 reproduce the same image as the other profiles of the OS2 series, creating an effect of continuity between the interiors and the exteriors of the building.

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OS2 65 is the thermal break window in precious metals, with minimal profiles of 27 mm, central node between the two sashes of only 62 mm, depth of 65 mm for glass up to 40 mm. 

The system is the only one that has all types of openings, giving you the option to always have the same section in sight.

OS2 75 is the thermal break window in precious metals, with minimal profiles of 27 mm, central node between the two windows of only 62 mm, depth of 77 mm for glass up to 50 mm. The system is the only one that has all types of openings, tilt and turn, bi-folding, pivot, lift and slide, anti-burglary, providing you with the option to always have the same section in sight.

There are more than 40 profiles to choose from, where you can find solutions for any formal or functional project requirement. The profiles can house flush-mounted and non-flush-mounted glass panels, enhance the borders of the monocoloured area of the windows that make up the front, or render them imperceptible to the eye, put fixed or openable sashes correspondingly in the design of the façade. To better distinguish the various choices available, we have created two subsystems: OS2 75.1 and OS2 75.2.

• Ultra-Slim Sightlines & Elegant Design: OS2 profiles have award-winning Italian styling. With side sections as narrow as 27 mm, they “dematerialize” walls and flood interiors with natural light. The minimalist frames complement both contemporary and classical architecture. Optional finishes include matte black, any RAL color, or precious metals like copper or brass that age to a luxurious patina.

• High Thermal & Acoustic Performance: All OS2 windows are thermally broken steel windows, using polyamide/polyurethane strips between inner and outer metal. This interrupts heat transfer so effectively that OS2 systems routinely achieve passive-house level U-values (around 0.6–1.0 W/m²K) with triple glazing. The solid steel construction also provides excellent sound insulation, keeping interiors quiet and comfortable.

• Exceptional Strength & Security: Steel’s tensile strength is three times that of aluminum, allowing large panes and tall openings. Portamet’s OS2 windows withstand high wind loads and harsh weather; rigorous welding and gaskets make them airtight and watertight. For safety, Secco OS2 offers EBE fire-rated variants (up to EI90) and anti-burglary options, while standard frames easily meet strict security standards.

• Versatile Materials & Finishes: Beyond black-painted steel, Secco OS2 profiles can be made in architectural bronze (brass), stainless steel or Corten®. Brass frames give a warm bronze-like look that naturally weathers over time. With dozens of glazing beads and finishes, every window can be precisely specified for light, privacy, and aesthetic goals.

• Design Flexibility: Secco’s modular OS2 system has 40+ profile options, enabling virtually any configuration. Architects can mix fixed panes with operable casements, tilt-turns, sliders or folding doors, all using matching slim frames. This uniformity means a single project can maintain the same frame dimension on fixed and opening units, creating cohesive facades. The OS2-75 can accommodate oversized sashes (up to ~130×290 cm) and concealed hardware for a clean, modern look.

• Sustainability & Quality: Portamet’s steel windows are built to last. We use locally sourced, eco-friendly materials and powder coatings, and each frame is CE-certified and NFRC-ready. Steel is fully recyclable, and the extended service life of Secco windows means fewer replacements and reduced environmental impact.

• Residential Projects: Elevate modern homes, loft conversions, or upscale residences with floor-to-ceiling steel windows. Slim OS2 frames maximize light and views. For historic homes, we replicate classic steel or bronze frames exactly, blending heritage character with modern insulation. For example, the custom-arched steel window below preserves the original aesthetic while boosting thermal performance.
  Historic restoration: A custom arched OS2 steel window retains the traditional sandstone facade while delivering modern efficiency.

• Commercial & Institutional: Deliver a premium image for offices, hotels, restaurants, and schools. Secco OS2 frames are ideal for storefront glazing and lobby walls, offering expansive uninterrupted glass surfaces. The durable steel construction stands up to heavy use and weather, while maintaining airtight, leak-proof performance.

• Renovation & Heritage: Update museums, churches, and industrial buildings without altering their look. Secco’s BV series and OS2 profiles can match historic sightlines exactly. Fire-rated EBE windows allow safety upgrades in older structures. Our clients have preserved landmark facades by replacing old wood or steel sash with Portamet’s thermally-broken replicas.

• Specialty & Custom: From wine cellars to sky bridges, Secco OS2 excels where beauty and precision are paramount. Popular custom uses include interior glass partitions, glass roof domes, lift-slide patio doors, and multi-panel facades. Each element is engineered for perfection: OS2’s consistent frame sections ensure even sightlines across complex glass walls

Ready to specify the world’s finest steel windows? Portamet is here to help architects and developers with any size project. Request a free, no-obligation quote or discuss your design needs with our team today. Partner with us and bring Italian-engineered, thermally broken Secco OS2 steel windows to your next building.