Bernard Plancade, Managing Director at ROCKWOOL Core Solutions, explores how stone wool sandwich panels blend nature, fire resistance, and sustainability at a Welsh open-air museum.
The owners of the St Fagans National Museum of History in Cardiff wanted visitors to learn more about the rich world of Welsh craftmanship. For this, they needed a new space that would make for a comfortable viewing experience without creating stark contrast with the local environment. So the architects, Feilden Clegg Bradley Studios, designed a building that would immerse visitors in Welsh history and in the landscape at the same time.
The Gweithdy pavilion (named after the Welsh word for workshop) was built in 2018 to host hands-on demonstrations for crafts, and display around 500 artefacts. The low-lying building has a simple triangular plan so that the structure remains stable and strong, and it blends into the surrounding forest because of its natural materials and subdued colour palette.
Melding with nature
The architects wanted to match their aesthetic vision with long-lasting building performance. To achieve this, they selected sandwich panels with ROCKWOOL stone wool cores for the walls because they are highly durable and resistant to damage from moisture, cracking, and blistering.
These opaque panels are arranged vertically next to transparent glazing. A repetitive pattern of vertical timber strips, matching the colour profile of the local flora, helps integrate the building into its woodland site.
A peaceful atmosphere
Sandwich panels were also used inside as ceiling panels, mirroring the quietness of the surrounding woodland — they are microperforated, which means they give the building better sound absorption. The metal skin on the internal face reduces the metal surface by around 30% and allows sound waves to travel into the stone wool insulating core. This absorbs the sound energy to improve the quality of the building’s acoustics.
Fire resistance
Gweithdy features a built-in forge which is used for metalwork demonstrations and other heavy crafts activities. To keep visitors safe, the architects needed to use a material with excellent fire resistance. Stone wool is non-combustible, so using it as insulation in the building was the correct choice.
Stone wool insulated sandwich panels have an A2-s1, d0 fire performance classification, and provide fire resistance of up to two hours, allowing plenty of time for evacuation and emergency response in the case of a fire breaking out.
Staunch sustainability
ROCKWOOL’s stone wool technology plays a big part in Gweithdy’s sustainable design, which has achieved a BREEAM ‘Excellent’ rating. Architects earn BREEAM credits for addressing factors that influence sustainability in 10 categories. Only 10% of buildings achieve ‘Excellent’, which requires earning at least 70% of the maximum possible number of credits.
Of the BREEAM categories, stone wool insulated sandwich panels contribute to sustainability in building management, health and wellbeing, safety, energy, materials, and waste.
The panels slash energy consumption significantly over the building’s lifetime. They also improve indoor air quality because stone wool is non-toxic, resistant to mould, and doesn’t release harmful chemicals or particles into the air. And due to their longevity, sandwich panels help architects earn BREEAM credits throughout a lifetime of up to 50 years, with even further potential for end-of-life reuse and recycling.
The pavilion was recognised in 2019 as one of the top buildings in Wales by the Royal Society of Architects in Wales (RSAW), who said: “The building has been designed to be a simple, but environmentally responsive form, and it does not fail to deliver this ambition in its calm, simple, and sustainable execution.”
A new stone age
ROCKWOOL has supported many architectural projects with stone wool for sandwich panels over the years, including Gweithdy. It recently showcased its expertise through the publication of the first-ever guidebook on the technology. Written by Professor Marco Imperadori from the Politecnico di Milano, in partnership with ROCKWOOL Core Solutions, ‘Building with Stone Wool Insulated Sandwich Panels’ bridges an industry knowledge gap about the material.
It serves as a practical resource for manufacturers, architects, builders, and contractors, helping them choose more sustainable and fire-safe building materials. This knowledge is essential for the creation of buildings like Gweithdy, which blend form, style, and function to bring culture to life.
The ‘Building with Stone Wool Insulated Sandwich Panels’ guide can be read here.
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