A Door Grown from Fungi: Denmark's Startup Launches Mycelium Interior Doors
- Gauri Khanna
- Apr 13
- 3 min read
Danish mycelium company Rebound and Det Levende Hus have developed a prototype interior door with a core grown from cultivated fungi, framed in reclaimed timber.
The door is designed to meet current Danish building standards for fire and moisture resistance, and will be installed at Kaerhytten, a low-impact housing project in Ramloese, Denmark, scheduled for completion in 2026.
The growing process takes approximately two weeks; once the panel is grown and an internal reinforcing layer has been bio-welded in place, no additional finishing is required, which the team argues makes industrial-scale production viable.
Danish startup Rebound and architecture studio Det Levende Hus have produced what they describe as the world's first mass-produced interior door with a mycelium core: and it is set to be installed in a low-impact housing project later this year.
From Agricultural Residues to Architectural Components
Interior doors are not the most glamorous subject in sustainable design, but they are a useful test case. A standard hollow-core interior door typically contains a timber frame surrounding a honeycomb cardboard fill, topped with a thin facing of MDF or veneer. The result is lightweight but acoustically thin and, if made from virgin materials, carries a non-trivial environmental footprint. Solid timber doors perform better acoustically and structurally, but rely on slow-growing hardwoods whose supply chains are under increasing scrutiny.
Mycelium composites are materials grown by cultivating fungi through agricultural or forestry residues, which the fungal threads bind together into a rigid foam-like structure. They have been proposed as an alternative fill material for years. The challenge has been moving from laboratory panels to products that meet the performance requirements of real buildings. The collaboration between Rebound and Det Levende Hus, represents one of the more concrete attempts to clear that bar.
How the Door Is Made
The process follows the standard logic of mycelium composite production: fungi are cultivated in a mould, spreading their fine hyphea networks through a substrate and binding it into a rigid panel as they grow. What makes this application more technically specific is the integration of a bio-based reinforcing layer during the growing process itself: a technique the team describes as "bio-welding." Rather than adding structural reinforcement as a separate manufacturing step, the reinforcement is incorporated while the material is still biologically active, bonding to the growing mycelium without adhesives. The result, according to the developers, adds stiffness and improves fire resistance simultaneously.
The mycelium core is enclosed within a frame of reclaimed and surplus timber, including offcuts from Danish flooring manufacturer Dinesen; this is a deliberate choice that keeps the bill of materials within the circular economy rather than drawing on new resources. The outer surface can be finished with a layer of clay, or left as grown, presenting a smooth texture whose colour and surface character can be adjusted during cultivation by varying growth conditions.
The growing cycle takes approximately two weeks. Once complete, the panel requires no additional processing before assembly which is a potential advantage over conventional door cores, which typically require cutting, pressing, and adhesive bonding of multiple components.
Meeting Building Standards: Fire, Moisture, and Acoustic Performance
The prototype was designed to comply with Danish building standards for private residential use, specifically with regard to fire and moisture resistance: the two properties that most often disqualify bio-based materials from architectural specification. The bio-welded reinforcing layer contributes to fire resistance; moisture resistance is addressed through the material's formulation, though the developers have not yet published detailed performance data.
Acoustic performance is one area where mycelium composites have a natural advantage. The open, porous cellular structure of fungal materials, similar in principle to the air pockets in rockwool or cork, absorbs sound rather than reflecting it. This is relevant for interior doors, where sound transmission between rooms is a common complaint in residential construction. Mycelium's acoustic properties have already been demonstrated at larger scale, including in acoustic panels grown for a dance music tent at the Glastonbury festival.
Scalability and the Path to the Mass Market
The door will be used for the first time at Kaerhytten, a low-impact housing project by architect Jens Martin Suzuki-Højrup in Ramloese, Denmark, due for completion in 2026. The project is a relatively modest initial deployment, but serves as a proof of concept for integration into a functioning building under real occupancy conditions: a step beyond exhibition installations and trade show prototypes, which have previously been the primary showcase for mycelium architectural products.
Rebound is also developing acoustic wall panels and ceiling products using the same material platform, suggesting a broader interior fit-out proposition rather than a single novelty item. Whether these products can reach price parity with conventional alternatives at volume remains to be demonstrated. Mycelium composites are not yet cheap to produce at scale; the economics depend on substrate cost, cycle time, and the degree to which premium positioning in the sustainable construction market can offset higher unit costs.
