Heritage Units
Technical, slim-profile glazing designed for period, conservation and listed buildings.
Heritage glazing units are specifically engineered for homes where the appearance of traditional single glazing needs to be maintained but improved performance is essential. These slim double-glazed units provide enhanced thermal efficiency, clearer sightlines and a more comfortable living environment, all while keeping the delicate detailing of period timber windows.
This page explains what heritage units are, how they work, their construction options and their advantages compared with other glazing solutions.
What are Heritage Glazing Units?
Heritage units are slim, lightweight double-glazed units designed to replicate the look of traditional single glazing. They are ideal for:
- Sash windows
- Casement windows
- Wooden window replacements
- Listed and conservation area properties
These units allow homeowners to benefit from energy improvements without altering the external appearance of historic joinery.
Slim Double Glazing Explained
Traditional double glazing is often too thick for period window frames. Heritage units solve this problem by using:
- Reduced cavity depths
- Slimmer glass thickness
- Minimal sightlines
- Discreet perimeter seals
Typical overall thicknesses are significantly thinner than standard double glazing, allowing heritage units to be installed in:
- Original frames (where suitable)
- New like-for-like timber replacements
- Narrow sash and casement profiles
Slim double glazing preserves the proportions and detailing of period windows while improving comfort inside the home.
Inert Gas Technology
Heritage glazing units often use inert gas, such as argon, in the cavity between the panes. This enhances thermal performance without increasing the thickness of the unit.
- It conducts heat more slowly than air
- It helps maintain internal room temperature
- It reduces the risk of condensation
- It improves the overall effciency of the unit
The combination of slimline construction and inert gas insulation makes heritage units a strong choice for energy-conscious homeowners who must also meet conservation requirements.
Energy Performance and U-Valves
Although slimmer than standard double glazing, heritage units still deliver noticeable energy improvements compared with single glazing.
Typical performance advantages include:
- Reduced heat loss through the glass
- Lower heating bills
- More stable room temperatures
- Warmer internal glass surfaces
- Reduced cold spots and draughts
While the exact U-value depends on the unit’s construction, heritage units generally outperform traditional single glazing by a significant margin, helping older homes feel more comfortable throughout the year.
Visual Appearance and Sightlines
A key advantage of heritage units is their ability to retain the visual authenticity of single glazing. This is essential for:
- Listed buildings
- Conservation area properties
- Period homes with strict planning constraints
Heritage units achieve this by:
- Using very slim edge seals
- Keeping perimeter lines discreet
- Maintaining traditional glass proportions
- Allow timber glazing bars to sit naturally
- Avoiding the bulky look of standard double glazing
The result is a window that looks period-correct but performs to modern expectations.
Advantages of Heritage Glazing Units
Heritage glazing provides a balanced solution for improving comfort while retaining original character. Key advantages include:
- Suitable for planning-sensitive homes
- Slim design allows installation in narrow timber frames
- Enhanced insulation without altering the window apperance
- Improved acoustic performance
- Low-iron glass options for brighter, clearer views
- Lightweight construction ideal for sash balance and movement
- Durable sealed units designed for long-term use
Heritage Units vs Secondary Glazing vs Vacuum Glazing
Each option has different strengths depending on planning restrictions, window condition and energy goals.
Installation in Existing Window Considerations
When assessing whether heritage units are suitable in your existing windows, the following factors matter:
- Condition of existing frames
- Available rebate depth
- Type of glazing bars (integral or applied)
- Requirement of the local conservation officer
- Weight and balance considerations for sash windows
- Expected performance and longevity
A site visit is often required to confirm suitability.
Explore our product range
Case Studies
Explore our recent projects, from elegant Georgian townhouses to country cottages and listed restorations. See how our timber windows and wooden window replacements have transformed these buildings.
Our Story
Proudly family-run for over 20 years. Every timber window, door and wooden window frame is hand-built in our Wiltshire workshop and installed in homes across Salisbury, Dorset and Hampshire by skilled local craftspeople.
Areas we cover
We work with period properties, conservation areas and modern homes, delivering expert craftsmanship and a personal service.
Whether you're in a market town or countryside cottage, we bring over 20 years of experience in traditional timber joinery and restoration to your project.
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