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.
A complete service
from design to installation.
We purchased a combination of Alu-Clad windows, Lift & Slide doors and entrance glazing from Zyle Fenster for our family home.
Every member of the team was knowledgeable, approachable and highly professional. Manufacturing quality is outstanding and the installation was carried out with real attention to detail. Even after completion, they followed up to ensure everything was perfect.
It’s rare to find a company that delivers exactly what they promise. We would happily recommend Zyle Fenster to anyone building or renovating a home.
Seán & Emma R. – County Meath
Our architect specified Reynaers aluminium systems and recommended Zyle Fenster for the supply and installation.
The large glazing panels have completely changed the feel of the house while maintaining excellent thermal comfort throughout the winter. The installers were meticulous and every junction was finished beautifully.
It’s refreshing to work with a company that genuinely cares about delivering a quality result.
Niamh F. – County Clare
We chose Schüco aluminium windows and doors through Zyle Fenster for our contemporary home.
Everything about the experience was professional. From technical advice through to installation, the team demonstrated real expertise. The slim profiles look fantastic and the quality of the finish is exactly what we hoped for.
A premium product installed by a premium company.
David L. – County Waterford
Our conservation project required slim glazing without compromising performance, and Zyle Fenster recommended their vacuum glazed timber sash windows.
The result is outstanding. The traditional appearance has been preserved while the improvement in warmth and noise reduction is remarkable. You simply wouldn’t know they contain such advanced technology.
Excellent communication, excellent installation and an exceptional product.
Michael & Sarah K. – County Kilkenny
Finding authentic timber sash windows that also met modern energy standards wasn’t easy until we found Zyle Fenster.
The finished windows perfectly suit our Victorian home while dramatically improving comfort. They operate beautifully and the attention to detail is outstanding.
The installation team treated our home with great respect and left everything spotless each evening. We have received countless compliments from neighbours.
Margaret C. – Dublin
We wanted a large glazed feature overlooking the garden while still achieving excellent thermal performance. The timber curtain wall supplied by Zyle Fenster exceeded every expectation.
The craftsmanship is remarkable and the amount of natural light it brings into the house is incredible. Our architect was particularly impressed with the technical knowledge and attention to detail shown throughout the design process.
Professional, reliable and extremely high-quality workmanship.
Patrick D. – County Wicklow
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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