Aluclad Triple Glazed Timber Windows
An alu-clad version of 21 Degrees PERFORMANCE and ULTRA timber inward opening window ranges is now available. For environmental and maintenance reasons Green Building Store still recommends pure timber windows. However, aluclad windows are much in demand among selfbuilders and architects, so Green Building Store has introduced it now as an option for its inward-opening PERFORMANCE and ULTRA windows.
Premium Window Options
The new aluclad range offers an updated contemporary design with narrow installed sightlines with the timber frame designed to be wrapped within external wall insulation. For that reason, it is mainly designed for newbuild projects or deep retrofit, where there is the opportunity to ‘bury’ the frame within external insulation.
Key features
- Visible external sightline: 71mm (opening window)
- Partially exposed timber frame, for wrapping within external insulation
- FSC® certified timber in redwood & oak
Why Add Aluminium to Timber?
Combining aluminium with timber is a strategic upgrade that enhances both durability and thermal performance. Think of it as pairing natural warmth with engineered resilience.
Timber offers timeless beauty and excellent insulation, but it needs protection from the elements. That’s where aluminium comes in. Powder-coated aluminium cladding shields the timber from rain, UV rays, and pollution—eliminating the need for regular repainting or sealing. The result? A window that resists rot, warping, and decay while maintaining its aesthetic integrity for decades.
Insulation That Performs
Timber is naturally low in thermal conductivity, making it an exceptional insulator. When paired with aluminium cladding and triple glazing, aluclad windows can achieve U-values as low as 0.68 W/m²K, comfortably meeting Passivhaus standards and outperforming many conventional systems. This layered construction reduces thermal bridging and keeps your home warm in winter, cool in summer, and quiet all year round.
The Timber Inside: FSC-Certified and Purposeful
Most aluclad systems use FSC®-certified softwoods like pine or engineered hardwoods such as oak or meranti. These woods are chosen for their structural stability, sustainability, and ability to hold finishes beautifully. They flex subtly with seasonal changes, adding a tactile, organic quality to your interior while remaining dimensionally stable when protected by aluminium.
Choose 21 Degrees Aluclad Windows For:
Exceptional Thermal Performance
- U-values as low as 0.73 W/m²K, ideal for Passivhaus and ultra-low energy builds
- Argon-filled triple glazing acts like a “thermal sandwich,” keeping homes warm in winter and cool in summer
Versatile, High-Quality Ranges
- Multiple frame depths: GBS78 / GBS98 and aluminium-clad variants (GBS78-A / GBS98-A)
- Sliding sash option (GBS204SS) with class 4 airtightness for traditional aesthetics + modern performance
Certified Security & Airtightness
- Secured by Design multipoint locking systems
- Dual compression seals for long-term airtightness
- Fully tested for Part Q compliance, air tightness, and exposure
Sustainability & Craftsmanship
- FSC® certified timber—responsibly sourced and environmentally conscious
- Designed for deep retrofits, low-energy new builds, and certified Passivhaus projects
Customisation & Design Flexibility
- Wide choice of RAL colours and timber stains
- Multiple frame styles, hardware options, and glazing configurations
Installation & Aftercare
- Expert UK-wide installation team
- Friendly, responsive aftersales service with up to 10-year warranty
Technical Transparency
- PHPP-ready data and calculation reports available for all products
- Downloadable technical drawings and UKCA declarations
Discover the Best Aluclad Window Quality with 21 Degrees
With 25 years of experience in premium quality, ultra-efficient windows, we bring together cutting-edge engineering, timeless design, and sustainable craftsmanship to deliver aluclad windows that perform beautifully in every environment. Whether you're building to Passivhaus standards or simply seeking lasting comfort and style, our windows are designed to elevate your space—thermally, visually, and architecturally.
Contact 21 Degrees today to begin your journey to a more comfortable, healthier home.
