Preserving Heritage, Enhancing Performance: A 19th-Century Roof Renewal with NaturHeld Wood Fibre Insulation
How Build Greener helped deliver a warm, breathable, and sustainable roof upgrade.
Renovating heritage buildings demands a careful balance - preserving their timeless character while enhancing comfort, sustainability, and energy performance. At Build Greener, we understand that every decision, from material selection to installation method, plays a crucial role in achieving that balance.
Working in partnership with Kooka Construction, we recently supported the renewal of a 19th-century roof with a vaulted ceiling. The structure faced multiple challenges: failing timbers, a complete lack of insulation, and the need for modern upgrades without compromising its original form. Together, we delivered a solution that strengthened the building fabric while keeping its historic integrity intact.
By supplying and specifying NaturHeld FLEX wood fibre boards and NaturHeld 180 T&G insulation boards, Build Greener helped ensure the project achieved a balance between tradition and innovation. In partnership with Kooka Construction, we delivered a roof system that is structurally sound, highly efficient, fully breathable, and true to the building’s 19th-century character.
A 19th-Century Roof in Decline
The property was built in the 1800s and carried many of the hallmarks of traditional construction. Its vaulted ceiling gave the interior a sense of grandeur, but it also created restrictions: insulation couldn’t be installed internally without damaging the design. Externally, the roof timbers had warped, bowed, and twisted with age. The slates above them had seen better days, and the roof was no longer watertight.
Just as crucially, the roof offered no insulation whatsoever. In an era where energy efficiency is a necessity rather than a luxury, this left the property cold, draughty, and expensive to heat.
The homeowners were clear about their requirements. The new roof needed to:
- Strengthen the structure to meet modern standards.
- Deliver high performance insulation.
- Retain the original appearance of the building by reusing reclaimed slates.
- Align with sustainable values.
It was a tall order - but one that was achievable with the right combination of expertise and materials.
The Challenges of Heritage Roof Insulation
Heritage properties rarely come with straightforward solutions, and this project was no exception.
The first hurdle was structural deterioration. The roof timbers had deformed to such a degree that they could no longer be relied upon to support the slates or new insulation. Simply overlaying materials wasn’t an option; the structure itself had to be rebuilt.
The second issue was thermal inefficiency. Without insulation, the roof was responsible for significant heat loss. But because of the vaulted ceiling, no insulation could be introduced from below. This meant the insulation strategy had to be executed entirely above the ceiling line, while still ensuring breathability.
Third came the requirement of aesthetic preservation. The building’s historic value lay in its appearance. The homeowners wanted the upgraded roof to look as close as possible to the original, which meant that reclaimed natural slates had to be reinstalled in a way that didn’t compromise performance.
Finally, the solution had to reflect the client’s sustainability goals. Synthetic or non-breathable materials were unsuitable, both for environmental reasons and for the long-term health of the structure.
Step-by-Step Roof Renewal Process
Kooka Construction’s team devised a multi-layered strategy that delivered on every front: strength, insulation, breathability, and heritage preservation.
Removal and Assessment
The first stage was to carefully remove the old slates. Many of them were set aside for reuse, reflecting the client’s commitment to sustainability and conservation. Once stripped back, the true condition of the roof structure was revealed - bowed, twisted, and beyond reliable repair.
Rather than demolish the entire roof, Kooka Construction opted to build a new roof structure above the old one. This not only preserved aspects of the original but also ensured the new system met modern performance standards.
Between-Rafter Insulation
Next came the thermal upgrade. A breathable membrane was installed between the rafters to create trays. Into these, installers placed 2 layers of 50mm NaturHeld FLEX wood fibre boards.
NaturHeld FLEX was chosen for its versatility and performance. The boards fitted tightly within the rafter trays, eliminating gaps where heat could escape. Made from natural wood fibres, they also offered high thermal performance, vapour permeability, and sustainability - all crucial to the project.
Over-Rafter Insulation
To further improve the roof’s efficiency and eliminate cold bridging, an additional insulating layer was applied over the rafters. This was achieved using 40mm NaturHeld 180 T&G insulation boards.
These tongue-and-groove boards interlocked to form a continuous, airtight layer of insulation, maximising energy efficiency. Secured with RawPlug R-PTX TX 5x80mm fixings, the boards provided a durable and robust solution that complemented the between-rafter layer.
Weather Protection
With the insulation in place, Kooka Construction installed a second breathable membrane above the system. This layer shielded the roof from external weather conditions while still allowing moisture vapour to escape, ensuring the roof remained healthy and free from condensation risks.
Reclaimed Slate Finish
Finally, the team re-battened the structure and carefully reinstated the reclaimed natural slates. This finishing touch preserved the historic look of the building, meeting the client’s aesthetic requirements while completing a thoroughly modern warm roof system.
The Results: Performance Without Compromise
The renewed roof now stands as a perfect blend of traditional character and modern efficiency. With Build Greener’s NaturHeld insulation system, the structure delivers exceptional thermal performance - keeping the property warmer, more comfortable, and more economical to heat.
Because the materials are vapour-open, the roof retains its ability to breathe, protecting the original timbers from condensation and moisture damage - a crucial consideration in any heritage restoration. And by reusing reclaimed slates, the project preserved the roof’s historic charm while minimising waste and environmental impact.
The result is a success story for both heritage and sustainability - and a great example of how Build Greener materials can help homeowners enjoy the best of both worlds: a roof that respects the past while embracing the future.
Lessons for Future Retrofit Projects
This project highlights the possibilities of sympathetic retrofits for heritage buildings. It shows that upgrading performance does not have to mean sacrificing authenticity. By selecting the right combination of natural, breathable insulation and reclaimed materials, it’s possible to create outcomes that are sustainable, efficient, and true to a building’s history.
Materials That Made the Difference
At Build Greener, we supplied and specified the insulation system that made this transformation possible - combining modern wood fibre technology with breathable design principles.
NaturHeld FLEX Wood Fibre Board (50mm)
For this project, we chose the NaturHeld FLEX 50mm wood fibre board as the primary insulation layer beneath the roof covering. This material is made from sustainably sourced wood fibres, offering excellent thermal and acoustic performance while remaining fully breathable - a crucial factor in heritage buildings.
In a 19th-century roof, where managing moisture and allowing the structure to “breathe” is vital, the open-pore structure of wood fibre helps regulate humidity naturally. It prevents condensation build-up that can damage original timbers over time. The density of the board also adds sound insulation and contributes to overall comfort within the home.
Beyond performance, NaturHeld FLEX supports eco-conscious restoration, aligning with the values of modern sustainable building while respecting the integrity of the original structure.
NaturHeld 180 T&G Insulation Board (40mm)
On top of the flexible insulation layer, we chose the NaturHeld 180 tongue-and-groove (T&G) 40mm insulation board. This rigid layer provides an additional thermal break and ensures a tight, continuous insulation envelope with minimal thermal bridging. The precision T&G edge profile means the boards interlock seamlessly, improving airtightness and overall energy efficiency.
Because it’s also vapour-permeable, the NaturHeld 180 works in harmony with the FLEX board below it, maintaining the roof’s breathability while enhancing structural stability. Its rigidity makes it ideal for use beneath battens or roof membranes, helping to create a smooth, even surface for re-tiling or slating .
Why They Were the Right Choice
Combining NaturHeld FLEX and NaturHeld 180 T&G allowed us to deliver a roof system that is:
- Thermally efficient – dramatically reducing heat loss without compromising the building’s historic character.
- Moisture-smart – breathable materials that protect old timbers and plasterwork from trapped damp.
- Sustainably sourced – made from renewable wood fibres with a low embodied carbon footprint.
- Heritage-friendly – compatible with traditional roof structures and sensitive restoration practices.
Together, these materials embody the balance that Build Greener and Kooka Construction strives for: modern performance, traditional integrity, and environmental responsibility.
Blending Heritage and Sustainability
This 19th-century roof renewal showcases how Build Greener’s sustainable insulation systems can help restore historic buildings without compromise. Working alongside Kooka Construction, we delivered a roof that performs to modern standards while preserving its authentic appearance.
Whether you’re renovating a heritage property or designing a low-carbon new build, Build Greener offers a wide range of sustainable building materials - from natural insulations to breathable boards and eco-friendly products.
For us, sustainability is about more than efficiency. It’s about creating comfortable, durable spaces that respect both the planet and the craftsmanship behind great buildings. From first conversation to completion, we’re here to provide honest advice, reliable materials, and solutions that last.
📧 Get in touch: sales@buildgreener.co.uk
🌐 Explore our solutions: www.buildgreener.co.uk
Let’s build projects that protect history - and the future.