McLean Museum & Art Gallery

Kalwall Atrium Roof Retrofit Case Study

Overview

The McLean Museum and Art Gallery, part of the Watt Institution complex in Greenock, Scotland, is one of the region’s most significant cultural buildings. The museum houses a wide collection of historical artefacts, artwork, textiles, and cultural objects that require carefully controlled environmental conditions to preserve their integrity.

As part of a broader refurbishment of the Grade-A listed building, a major challenge centred on the building’s large atrium roof. The existing glass roof allowed uncontrolled daylight into the space, creating a long-standing conflict between providing natural light for visitors and protecting sensitive artefacts from damage caused by ultraviolet radiation and solar exposure.

Structura was appointed to deliver the installation of a new roof glazing system that could resolve this issue. The project required a solution capable of introducing natural daylight back into the atrium while protecting artefacts and preserving the historic character of the building.

The final solution involved the installation of a double-pitched Kalwall roof system, designed to provide high levels of daylight transmission while filtering harmful ultraviolet radiation. The result transformed the previously darkened atrium into a naturally illuminated space while maintaining strict conservation standards for museum displays.

Project Metrics

Key performance and project metrics include:

Building Type: Grade-A listed museum and gallery
Roof System: Double-pitched Kalwall translucent roof
Glazing U-Value: 0.57 W/m²K

Performance Improvements

• Full UV-A and UV-B protection for artefacts
• Reintroduction of natural daylight to the atrium
• Reduced reliance on artificial lighting
• Improved thermal performance
  

Construction Benefits

• Existing structural frame reused
• Reduced construction waste
• Lower environmental impact of installation

The Challenge

Refurbishing glazing within historic cultural buildings presents a unique combination of architectural, conservation, and engineering challenges. Museums must balance the need for natural light with strict environmental controls that protect fragile artefacts from deterioration. At the McLean Museum and Art Gallery, the original atrium roof had created a long-standing problem for curators and building managers.

Protecting Sensitive Artefacts from Solar Damage

Many materials found in museum collections are highly vulnerable to degradation caused by ultraviolet radiation and prolonged exposure to direct sunlight. Examples include paint and varnish layers on artworks, textiles and historic fabrics, wood artefacts, pigments and dyes used in paintings and objects, and paper documents and archival materials. Exposure to ultraviolet radiation can cause fading, chemical degradation, and structural weakening of these materials over time. For this reason, museums often carefully control daylight levels and sometimes rotate displays to limit exposure. In the case of the McLean Museum, the original glass roof allowed large amounts of direct sunlight into the atrium space. This created an environment that posed risks to artefacts on display.

A Darkened Atrium Environment

In order to mitigate this problem, the existing roof glazing had been covered with layers of black paint to block out daylight and reduce solar radiation. While this helped protect artefacts, it created a new problem. The atrium became a dark and uninviting space, significantly reducing the quality of the visitor experience and diminishing the architectural impact of the historic building. The challenge was therefore to reintroduce natural daylight into the building while still protecting artefacts from harmful radiation.

Structural Constraints of a Historic Building

Because the museum is a Grade-A listed building, any new roofing solution had to respect the original architectural character and structural limitations of the historic structure. Large structural changes were not feasible. The replacement glazing system needed to integrate with the existing roof framework without placing excessive loads on the structure. This made material weight, installation method, and compatibility with the existing support system critical considerations in the design of the solution.

Structura’s Solution

To resolve these challenges, Structura implemented a Kalwall translucent roof system designed specifically for daylight-controlled environments such as museums, galleries, and public atriums. The selected system provided a combination of daylight transmission, UV protection, insulation performance, and structural compatibility with the existing roof structure.

Project Results

The installation of the Kalwall atrium roof successfully resolved the long-standing conflict between natural daylight and artefact protection at the McLean Museum and Art Gallery. The project delivered improvements in daylight quality, energy performance, and visitor experience while respecting the historic character of the building.

Restoration of Natural Daylight

The new Kalwall roof allows natural daylight to enter the atrium once again while diffusing the light to create a comfortable and visually balanced interior environment. Unlike the previous painted glass roof, which blocked daylight entirely, the new system provides evenly distributed natural illumination throughout the space. This improves the visual presentation of exhibits while restoring the architectural intent of the atrium as a naturally lit public space.

Enhanced Display Conditions for Artefacts

The Kalwall system transmits the full spectrum of visible light while filtering harmful ultraviolet radiation. This combination provides excellent colour rendering for artworks and artefacts, protection from UV-related degradation, and improved visual clarity for visitors. Artefacts can now be viewed under lighting conditions that better replicate natural daylight without compromising preservation standards.

Improved Energy Efficiency

The roof’s U-value of 0.57 W/m²K significantly improves the insulation performance of the atrium roof compared with traditional glazing systems. This reduces heat loss in colder months and helps maintain more stable internal temperatures throughout the year. In addition, the reintroduction of natural daylight reduces the need for artificial lighting, further improving the building’s overall energy efficiency.

Structural Efficiency & Reduced Construction Impact

Because the Kalwall panels are lightweight, the installation was able to reuse the existing structural framework supporting the roof. This delivered several measurable benefits, including reduced construction materials, lower project costs, less construction waste, and shorter installation time. Reusing the existing structure also helped protect the architectural integrity of the historic building.

Award Recognition

The success of the project was recognised within the architectural and conservation community. The refurbishment received several major industry acknowledgements. These recognitions highlight the project’s success in balancing heritage preservation with modern building performance, including:

• Special Conservation Award – Glasgow Institute of Architecture (2020)
• Shortlisted Finalist – AJ Retrofit Awards (2021)
• Shortlisted Finalist – RIAS Awards (2021)
  

Awards

Category: Curtain Walling, Kalwall, Skyroofs, Translucent Façades, Structura