Each window is built around a precision timber frame, sealed against the British weather and tailored to your home. Choose double or triple glazing, top or side-hung opening, or a fully reversible sash that allows the outside of the glass to be cleaned safely from inside.
The following specifications apply to our traditional double or triple glazed casement windows. Bespoke configurations are available for conservation and listed building projects with specific requirements.
| Product guidance – as standard | |
| Frame | 56 x 90 mm (standard). Manufactured using mortise and tenon joints, glued and mechanically fixed |
| Sash | 46 x 68 mm (standard) |
| Sill projection | 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm |
| Wood moisture content | 12–19% |
| Glazing beads | Internally beaded |
| Product Specification | |
| Material | Engineered redwood (standard). Engineered hardwood, Accoya, European oak optional |
| Finish | Three-coat spray-applied factory finish using water-based microporous paint/stain |
| Colour | White – RAL 9016 (standard). Any RAL from RAL Classic range. Stain from stain range |
| Glazing | Double glazed, 4/16/4 Low-E (standard). Triple glazing optional |
| U-value | 1.2 W/m²K double glazed – 0.8 W/m²K triple glazed |
| Perimeter spacer bars | White warm edge perimeter spacer with white warm edge integral spacers (standard). Silver and black optional |
| Frame profile moulding | Ovolo 22 mm, Ovolo 18 mm, Lambs Tongue 22 mm, Lambs Tongue 18 mm |
| Trickle ventilation | Through sash head trickle ventilator. EA 1700, 4400, 5000 mm² |
| Security | Can conform to PAS 24. Secured by Design (SBD) certified |
| Glazing bars | Applied 18 mm and 22 mm glazing bars to external faces of glazed unit |
| Operation | Top hung, side hung, or fully reversible |
Download brochures and full product datasheets for the Traditional Timber Casement Window range.
The installation of timber casement windows in a listed building or conservation area demands an exceptional level of precision and period sensitivity. Our traditional double or triple glazed casement windows are manufactured to replicate the exact profiles, mouldings, and glazing bar arrangements of original historic casements – to the point that the replacement is virtually indistinguishable from the original.
We work with architects, conservation officers, and heritage homeowners to ensure every window meets both planning requirements and performance expectations. From the traditional putty glazing and solid ovolo bars to the choice of microporous paint finishes and heritage ironmongery, our timber heritage casement windows are a perfect fit for the most demanding conservation projects.
Heritage does not mean sacrificing insulation or energy efficiency. Our traditional double or triple glazed casement windows are available with slim double glazing – a 4/6/4 Low-E unit – designed to sit within a traditional putty-glazed profile, delivering measurably improved thermal performance and reduced heat loss compared to original single-glazed casements without altering the window’s visual character.
Acoustic performance is also considered in our design, with the timber frame providing natural sound attenuation and the option for upgraded glazing specifications where noise reduction is a priority. Available in a full range of RAL colours and stain finishes, these windows are an excellent option for homeowners and specifiers seeking the perfect balance of sustainability, durability, and authentic period aesthetics.
Traditional casement windows offer the perfect balance between traditional design and contemporary performance. With authentic detailing and a choice of timber frames, they suit both restoration projects and new developments aiming for a heritage look. Improved glazing options ensure better insulation and acoustic comfort.
Honest answers to the questions homeowners, self-builders and design teams ask most often when choosing a timber casement window.
With triple glazing, whole window U-values of 0.8 W/m²K are achievable, eliminating cold spots near windows and helping reduce heating bills throughout the colder months.
A fully reversible option allows the outside face of the glass to be cleaned safely from inside the home, particularly useful for upper-storey windows and properties with limited external access.
Engineered redwood is our most popular choice. Accoya offers exceptional long-term durability, while European oak gives a richer grain and presence for visible interior joinery.
Each window can be specified to Secured by Design and PAS 24 standards, with multi-point locking and laminated glazing options for ground-floor and accessible windows.
With routine maintenance and periodic recoating, a Zyle Fenster timber casement window has an expected service life of decades, supported by our manufacturing and finish guarantees.
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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