Many church communities and organizations operating in heritage buildings are committed to reducing their environmental impact and lowering heating costs. Their goal is to create sustainable churches that remain accessible to everyone for various activities. However, these large spaces often require significant energy to heat and suffer from loud reverberation. With the current gas crisis and strict government regulations on CO2 emissions for monuments, hosting events during colder months has become increasingly financially challenging. 

To ensure a sustainable future for generations to come, it is our responsibility to find long-term solutions that both preserve the original architecture and work in harmony with it. At Belén, we asked ourselves: How can we maintain these sacred spaces, knowing that we are merely visitors in time? 

Every building and community is unique, situated within its own environmental context, which creates different requirements for thermal and acoustic insulation. This diversity inspired the materiality of our project. Fibre Walls is a stucco layer made from textile fibers sourced from residual flows of fabric producer Kvadrat, currently being developed by Belén in collaboration with HuisVeendam. Designed as a mono-material, it serves as both an aesthetic finish and an integrated solution for thermal and acoustic insulation. Additionally, it is completely circular and biodegradable. 

The Willibrordus Church, located in Haringhuizen, a village in North Holland, Netherlands, has roots that trace back to medieval times. Positioned on fertile farmland, the church is deeply connected to the region’s cultural heritage and ecosystem. Originally built in the twelfth century, the church's Romanesque structure was expanded until the fifteenth century. By 2024, the church has evolved from being solely a place of worship to a communal gathering space. The villagers care for it and host events for both locals and visitors. 

With an estimated 3,000 churches in the Netherlands expected to lose their religious function in the next decade, Belén reflects on the changing significance of such monuments over time and across different contexts. 

The architecture of the Willibrordus church has experienced many changes throughout its long history. The north aisle was demolished, followed by the choir space in 1842.  

The church continued to evolve, and until that year, it had a choir extending from what is now the east wall, which remains the coldest part of the structure today. To address this, Belén visually revived the choir’s architecture on this wall with a wool drawing, recognizing that insulating this area would greatly improve the building’s comfort and energy efficiency. By delving into the church’s archives, the design team uncovered the original plans for the choir, enabling a virtual reconstruction of the church’s former shape. 

This historical blueprint inspired the creation of a new stucco wall, with wool meticulously recreating the contours of the original choir. The design subtly reveals the past, forging a tangible connection to a sustainable future while embedding the rich history of Willibrordus Church. 

Fibre Walls can be composed from various textile fibers, but wool was chosen for the Willibrordus Church for two key reasons. First, research has demonstrated that wool possesses excellent thermal, acoustic, and moisture-regulating properties. Second, wool has a deep connection to Haringhuizen, a village historically and presently linked to sheep herding. The Fibre Wall serves a dual purpose: it functions both as an effective thermal and acoustic insulation layer and as an aesthetic finish, thoughtfully reflecting the church’s rich history.