The EcoTherm flush casement window is built around a thermally efficient timber core, clad externally in polyester powder-coated aluminium. The flush sash profile creates clean lines that sit naturally within contemporary and heritage architectural styles, while internally beaded glazing, warm edge spacer bars, and a three-coat microporous factory finish deliver a premium solution from frame to glass.
Full specification details for the EcoTherm SL flush casement Aluclad window, covering both double-glazed EcoTherm and triple-glazed EcoTherm+ configurations.
| Product guidance – as standard | . |
| Frame | 50 x 102 mm - for Double Glazed EcoTherm and 50 x 112 for Triple Glazed EcoTherm+ window. Manufactured using mortise and tenon joints, glued and mechanically fixed. |
| Sash | 55 x 58 mm- for Double Glazed EcoTherm and 65 x 58 for Triple Glazed EcoTherm+ window. |
| Sill projection | 110 mm, 150 mm, 180 mm, 210 mm. |
| Wood moisture content | 12-19% |
| Glazing Beads | Externally beaded. |
| Product specification | . |
| Material | Engineered redwood - Standard. Engineered hardwood, Accoya, European oak. |
| External finish | Polyester powder coating. |
| Glazing | 28mm Double glazed unit of 4/20/4 Low-E - as standard for EcoTherm. 48mm Triple glazed, 4/18/4/18/4 Low-E - as standard for EcoTherm+. |
| Perimeter spacer bars | White warm edge perimeter spacer- as standard. Silver and black spacer optional. |
| Trickle ventilation | Through frame head trickle ventilator. EA 1700, 4400, 5000 mm2. |
| Internal finish | Three coat spray applied factory finish using water-based Teknos micro-porous paint/stain. |
| Colour | White - RAL 9016 - Standard. Any RAL - from RAL classic range. Stain - from TRC stain range. |
| U-value | Uw=1.2 W/m²K for double glazed EcoTherm window. Uw=0.8 W/m²K triple glazed EcoTherm+ window. |
| Frame profile moduling | Square sash and frame profile as standard. Ovolo profile for sash and frame optional. |
| Security | Complies to PAS 24 enhanced security standard. |
Download the EcoTherm flush casement window datasheet, specification guide, and BIM files for use in your project documentation.
The EcoTherm flush casement Aluclad window is designed for projects where clean lines and a flush, planar sash profile are architecturally important. Unlike standard casement windows, where the sash sits proud of the frame, the EcoTherm sash sits flush – creating an uninterrupted surface that suits both sleek contemporary façades and the proportions of traditional homes and period properties.
The fully reversible sash is a practical and important feature for multi-storey and high-rise applications. Sashes can be tilted inward for safe, easy cleaning from inside the building – making this window a highly practical specification choice across a wide range of applications, from private residential builds to apartment schemes and commercial developments.
The EcoTherm range is available with either double or triple glazing, making it adaptable to projects at different performance thresholds. The double-glazed EcoTherm configuration achieves a Uw of 1.2 W/m²K, while the triple-glazed EcoTherm+ reaches 0.8 W/m²K – an exceptional performance figure for a flush casement window, and well-suited to projects targeting energy efficiency beyond current building regulation minimums.
The aluminium exterior is finished in polyester powder coating across a full range of colours, allowing complete design flexibility for the external façade. Internally, the timber finish is factory-applied using water-based Teknos microporous paint or stain, available in white (RAL 9016) as standard, or any colour from the RAL classic range. For architects and clients seeking the highest industry standards of finish, specification, and thermal efficiency in a flush casement window, the EcoTherm is a considered and capable premium solution.
Our Aluclad flush casement windows bring together the elegance of traditional timber with the resilience of a contemporary aluminium exterior. Designed for outward opening with side- or top-hung options, they suit a wide range of architectural styles while offering excellent thermal efficiency through double or triple glazing. Slim sightlines and refined internal finishes enhance their appearance, while strong security credentials ensure lasting peace of mind.
Technical and specification questions about the EcoTherm flush casement Aluclad window, answered for architects, specifiers, and self-build clients.
Contact UsA flush casement window has a sash that sits level with the outer face of the frame, creating a flat, uninterrupted surface. This distinguishes it from standard casement windows, where the sash overlaps the frame visibly.
The double-glazed EcoTherm version achieves Uw 1.2 W/m²K. The triple-glazed EcoTherm+ achieves Uw 0.8 W/m²K, offering outstanding thermal performance suitable for low-energy and near-Passivhaus specifications.
Yes. The flush profile is historically accurate for many period property styles and is widely accepted by planning authorities for conservation areas, making the EcoTherm appropriate for both traditional homes and new builds.
Yes. The aluminium exterior can be finished in any colour from the RAL classic range. The internal timber can be painted or stained to match, with white RAL 9016 supplied as standard.
EcoTherm complies with PAS 24 enhanced security as standard. Through-frame head trickle ventilators are included, available in three equivalent area sizes to meet your ventilation specification requirements.
Whether incorporated into a modern contemporary new build or unlocking a period property, our curtain wall can reinvigorate a property by letting the natural daylight come flooding in.
Find out more about Dollar, ScotlandA complete service
from design to installation.
Zyle supplied Passive House windows for our new build, and the system met all project expectations. Airtightness and overall performance were delivered as specified, and their technical coordination on site was reliable and detail focused.
Private Owner
Mark Reynolds, Bristol
Our vacuum glazed sash windows provide an excellent balance between heritage sensitivity and modern performance. The slim glazing preserves the character of the property while significantly improving overall comfort. Installation was precise and professionally managed.
Private owner
Laura Mitchell, Southampton
The Passive House windows performed exactly as required within our project specification. Installation detailing, sealing, and overall execution were handled correctly, ensuring a high standard of delivery. A technically competent and reliable supplier.
Private Owner
Andrew Collins, Cambridge
We selected aluminum windows for their contemporary aesthetic and low maintenance. The proportions are well considered, and the finish quality is consistent throughout. Installation was efficient and carried out with strong attention to detail.
Private Owner
Rachel Adams, Reading
The triple glazed sash windows integrate seamlessly into the existing façade while offering a clear upgrade in comfort. Craftsmanship is evident in both joinery and installation, and the improvement in acoustic insulation is immediately noticeable.
Private Owner
Thomas Green, Nottingham
The Alu-Clad windows and doors introduced a strong architectural presence while maintaining a refined internal finish. Detailing, material quality, and consistency across the project are of a high standard. The process was structured and dependable from start to finish.
Private Owner
Olivia Bennett, Oxford
Whether you are an architect specifying for a new project, a self-builder planning your custom home, or a developer working to a programme, our team is here to help. Get in touch for technical advice, product information, or to request a quote.
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