The construction industry accounts for nearly 40 percent of global energy-related carbon dioxide emissions, making it a primary target for climate intervention. Most green building efforts aim for net-zero energy or carbon neutrality, where a building produces as much energy as it consumes or offsets its emissions through purchased credits. A smaller and more ambitious category is the climate-positive building, which removes more carbon from the atmosphere than it emits over its lifecycle. The Green Solution House hotel on the Danish island of Bornholm is expected to achieve this status with a new wing built, clad, and insulated entirely from wood. The project team used climate consultant software to model building performance before finalizing the design, ensuring the wood envelope would meet both thermal and carbon targets.
What Makes a Building Climate Positive
A climate-positive building goes beyond net-zero by generating a net environmental benefit. The calculation considers three categories: operational carbon (emissions from heating, cooling, lighting, and appliances during use), embodied carbon (emissions from material extraction, manufacturing, transport, and construction), and biogenic carbon (carbon absorbed by plant-based materials during growth). For a wood building to be climate positive, the biogenic carbon stored in the timber must exceed the sum of operational and embodied carbon over an agreed time horizon, typically 60 years.
The Carbon Math Behind the Bornholm Hotel Wing
The Green Solution House extension includes 24 rooms, a conference room, and a roof spa. Every major component is wood: the structural frame is glulam timber, the exterior cladding is thermally modified wood, and the insulation is wood fiber board. Wood naturally absorbs CO2 as it grows, and that carbon remains locked in the material for the life of the building. The project team calculated that the carbon sequestered by the wood in the new wing would exceed the total emissions from construction, transport, and projected operational energy use over the building lifespan. This calculation includes the emissions from cutting, processing, and shipping the timber. The result makes this the first commercial building in Denmark with a positive climate footprint at the time of completion. Renewable energy systems complement the carbon math by supplying the building operational energy from Bornholm wind and solar grid, further reducing the operational side of the equation.
Carbon Storage Capacity of Common Building Materials
| Material | Carbon Storage (kg CO2e per m³) | Embodied Carbon (kg CO2e per m³) | Net Balance (kg CO2e per m³) | Renewable Resource |
|---|---|---|---|---|
| Cross-laminated timber (CLT) | -680 to -850 | 150 – 250 | -430 to -700 | Yes |
| Glulam timber | -600 to -750 | 120 – 200 | -400 to -630 | Yes |
| Reinforced concrete | 0 | 300 – 500 | +300 to +500 | No |
| Steel beam (recycled content) | 0 | 150 – 350 | +150 to +350 | Partially |
| Wood fiber insulation | -80 to -120 | 20 – 40 | -40 to -100 | Yes |
The net negative values for timber products show that wood actively removes carbon from the atmosphere rather than merely emitting less than alternatives. The Bornholm hotel maximizes this effect by specifying wood for the structure, cladding, and insulation, effectively creating a full carbon-storing envelope. Other climate-positive projects globally follow the same logic, using biogenic materials to offset the unavoidable emissions from foundations, transport, and mechanical systems.
How Wood Functions as a Structural and Insulating Material
Wood is not a single material but a family of engineered products with different structural properties. The Bornholm hotel uses glulam timber for load-bearing columns and beams, wood fiber board for insulation, and thermally modified wood for exterior cladding. Each product serves a specific role within the building envelope.
- Glulam consists of layered timber strips bonded with structural adhesive. It can span 20 to 30 meters without intermediate supports, making it suitable for hotel conference rooms and public spaces.
- Wood fiber board is made from waste wood chips compressed into rigid or flexible panels. It provides thermal conductivity between 0.038 and 0.045 W/mK, comparable to mineral wool, while adding vapor permeability that allows the envelope to dry naturally.
- Thermally modified wood cladding is heat-treated to 180 to 230 degrees Celsius, which alters the cellular structure to resist moisture and fungal decay without chemical preservatives. The treatment darkens the wood and reduces its equilibrium moisture content by 30 to 50 percent.
The combination of these three wood products creates a fully biogenic building envelope that performs thermally and structurally while storing carbon. The only non-wood elements in the envelope are the foundation and the roof membrane, representing a fraction of the total material volume. Contemporary construction methods for island sites have evolved to accommodate these engineered wood systems, with prefabrication reducing on-site assembly time and protecting materials from coastal moisture during construction.
Collaboration Between Architecture Firms and Sustainability Think Tanks
The Bornholm hotel project is a collaboration between three organizations: 3XN, an architecture firm with three decades of experience in human-focused design; GXN, a sustainability think tank specializing in circular design and materials research; and Green Solution House, the hotel operator that functions as a living laboratory for climate-friendly building solutions. This three-way structure allows each organization to contribute its specific expertise. 3XN handles the design and construction administration. GXN provides the research on material lifecycles, embodied carbon calculations, and circular economy strategies. Green Solution House operates the building and collects performance data that feeds back into the design of future projects.
The Role of the Living Laboratory
Green Solution House functions as more than a hotel. It is a showcase for sustainable building solutions where guests experience climate-positive construction firsthand. The building is fitted with sensors that monitor indoor temperature, humidity, air quality, and energy use. This data is shared with the design team to validate their models and adjust future projects. The conference rooms host events where building professionals can examine the wood construction up close. The roof spa provides a direct experience of the building relationship with the surrounding Bornholm landscape.
This type of structured collaboration is becoming more common as sustainability requirements grow more complex. The days when a single architect could specify all materials and systems from personal knowledge are giving way to projects where specialized consultants handle lifecycle analysis, carbon accounting, and circular material logistics. Learning from construction failures caused by coordination breakdowns reinforces the need for clear communication protocols between all parties, especially on projects that use innovative or untested material combinations.
Local Supply Chains and Regional Craftsmanship in Green Building
The Bornholm project deliberately worked with local companies for fabrication and installation. The wood was sourced from Scandinavian forests, processed at regional mills, and installed by local carpenters and joiners. This local supply chain reduces transport emissions, supports the regional economy, and ensures that maintenance and repairs can be handled with available skills and materials.
Bornholm has a strong tradition of wood craftsmanship from its maritime and building heritage, and the project tapped into that existing knowledge base. Proper vapor control and moisture management in the wood envelope was critical for the coastal island climate, where salt-laden air and high humidity could otherwise compromise the timber over time. The local builders understood these conditions from decades of working with wood in the same environment.
The decision to use local labor rather than importing a specialized timber construction crew had both cost and quality implications. Training the local workforce added several weeks to the pre-construction phase but eliminated the travel and accommodation costs of a specialized crew. More importantly, it left the island with a skilled workforce that can maintain the building and take on similar projects in the future. This is a replicable model for other managed construction on islands and remote sites, where developing local capacity reduces long-term costs and increases project resilience.
Circular Design Strategies for Hospitality Buildings
Circular design in hospitality goes beyond material selection. The Bornholm hotel wing was designed so that its components can be disassembled and reused at end of life. Mechanical fasteners replace adhesives where possible. The wood fiber insulation can be composted or remanufactured. The glulam beams can be re-sawn and re-engineered for a smaller building. These design choices anticipate a future where the building materials have value beyond their first use.
Circularity Assessment of Hotel Building Systems
| Building System | Material | Reuse Potential | Recyclability | Biodegradable |
|---|---|---|---|---|
| Structural frame | Glulam timber | High (re-sawn) | High (chipboard) | Yes |
| Exterior cladding | Thermally modified wood | Moderate (re-clad) | High (mulch/biomass) | Yes |
| Insulation | Wood fiber board | Low (compressed) | Medium (re-fiber) | Yes |
| Foundation | Reinforced concrete | Low | High (crushed aggregate) | No |
| Roof membrane | EPDM or TPO | Low | Medium (specialized) | No |
The table shows that the wood-based systems (frame, cladding, insulation) have high circularity potential, while concrete and membrane systems are more linear. The project minimizes the non-circular components by reducing foundation size through lightweight wood construction and selecting roof membranes with take-back programs from the manufacturer. These strategies reflect the broader principle that circular design requires thinking about every building layer from the start, not just the ones that are easy to make sustainable.