Vacuum-Glazed Sash Windows for a Listed Georgian Property, Bristol

Upgrading Traditional Georgian Sash Windows with Vacuum Glazing

For this listed Georgian property in Bristol, upgrading the original timber sash windows required a careful balance between improving thermal performance and preserving the building’s historic character, particularly given the building’s historic significance and the permissions required for alterations.

Ventrolla was appointed to manufacture and install four new pairs of bespoke Sapele hardwood sashes to the ground-floor front elevation, incorporating slim-profile vacuum glazing while retaining and repairing the existing timber box frames.

The project focused on a prominent four-part bay window, where traditional multi-pane glazing patterns, timber mouldings and architectural detailing were important considerations.

By replacing the existing sashes rather than the complete window assemblies, Ventrolla was able to introduce modern glazing technology while retaining much of the original window structure.

Four Pairs of Bespoke Sapele Hardwood Sashes

The project involved manufacturing four new pairs of timber sashes for the ground-floor bay window. Each pair was crafted in Sapele hardwood, with traditional Ovolo mouldings, solid glazing bars and Type B sash horns to complement the property’s existing architectural detailing.

The replacement sashes were designed to maintain the traditional multi-pane appearance of the windows, with careful consideration given to the proportions and glazing arrangement.

All four pairs were finished internally and externally in Teknos Standard White, providing a consistent appearance across the front elevation.

Polished brass Brighton sash fasteners, sash lifts and sash restrictors completed the detailing, combining traditional ironmongery with practical functionality.

Improving Thermal Performance with Vacuum Glazing

A key feature of the project was the introduction of 10.3mm PG vacuum glazing to both the upper and lower sashes of all four window openings.

Unlike conventional double glazing, vacuum glazing uses a vacuum between two panes of glass to provide thermal insulation within a relatively slim unit.

This makes it a potential option for heritage properties where the appearance and proportions of traditional sash windows are important considerations.

For this Georgian property, the vacuum-glazed units were incorporated into newly manufactured Sapele hardwood sashes, allowing the glazing to be accommodated within carefully designed timber sections.

The result was a modern glazing upgrade that maintained the traditional multi-pane appearance of the bay windows.

Retaining and Repairing the Existing Timber Frames

Although all four pairs of sashes were replaced, retaining the existing timber box frames remained an important part of the project.

Each window required a replacement timber cill to address deterioration at the base of the existing frames.

The left-hand bay window also required additional splice repairs to the lower sections of the frame jambs, including the outer right jamb and inner left jamb.

These targeted repairs addressed areas of damaged timber while allowing the surrounding original joinery to remain in place.

All four window openings received a thorough overhaul alongside the installation of the new sashes, ensuring the existing frames were prepared to accommodate the replacements.

The retained sash box frames were also painted internally and externally on site, completing the refurbishment of the existing timberwork and providing a consistent finish across the bay.

Draught-Proofing and Easier Future Maintenance

Alongside the vacuum glazing, Ventrolla incorporated its Perimeter Sealing System (VPSS) into each of the four window openings.

The system helps reduce draughts around the moving sashes, improving everyday comfort while maintaining the traditional operation of the windows.

Each window also received Ventrolla’s Sash Removal System (SRS), designed to make future maintenance and decoration more straightforward.

By allowing the upper and lower sashes to be removed more easily, the SRS provides improved access to the existing box frames without unnecessarily disturbing the surrounding joinery.

Together, these systems complemented the new vacuum-glazed sashes, combining improved window performance with practical long-term maintenance benefits.

Preserving Georgian Character with Modern Glazing

The project brought together four pairs of bespoke vacuum-glazed replacement sashes, traditional timber detailing and targeted repairs to the existing window frames.

By retaining the original box frames, replacing deteriorated cills and carefully matching the new sashes to the property’s architectural character, the work provided a considered approach to upgrading the windows of this listed Georgian building.

The use of vacuum glazing demonstrates how modern glazing technology can be incorporated into bespoke timber sashes while respecting the proportions and appearance of historic windows.

Specialist Sash Window Replacement for Listed Georgian Properties

Ventrolla specialises in the restoration, renovation and bespoke replacement of traditional timber sash and casement windows in Georgian, Victorian and Edwardian properties.

From repairing original timber frames to manufacturing bespoke replacement sashes with heritage double glazing or vacuum glazing, our approach focuses on preserving architectural character while improving comfort, performance and longevity.

For more information about our specialist heritage window services, visit ventrolla.co.uk or contact our team on 0800 0277 454.