The conclusion was that wood is three to five times more resistant to fire than concrete or bricks. A thick wooden block does not burn, but only becomes charred on the surface. Wood’s fantastic static properties are also retained much longer at extremely high temperatures in comparison with reinforced concrete structures, for example.
These related to the fire safety of the solid wood components, the air-tightness and safety of condensate formation within the outer wall structure, and the façade cladding.
A fire safety concept was set out for the “WOODCUBE” in conjunction with the Technical University of Darmstadt.
Exemptions were granted on the design of the building components in the areas of burn rates, fire protection, and flue gas risk analysis.
Due to the system-dependent features (dowelled cross-laminated timber elements and the outer wall structure with largely non-ventilated façades), specific checks had to be carried out as part of the planning process.
The fire safety requirements for multistorey residential buildings are easily met at the “WOODCUBE”, although the relevant building regulations and technical rules do not yet stipulate this level of quality. The building was approved through individual allowances in all areas.
Given that the floor height of the top (fourth) floor is approximately 12.20 m above the surface at the middle of the site, and the units in use are less than 400 m2 in size, the building meets § 2 (3) of the regulations for buildings in Class 4 (GK 4).
The timber used in “WOODCUBE” comes from local forests. By eliminating fire-protective encapsulation, the building components could remain visible on the inside. This meant that there was no need for additional coatings or protective structures, while the indoor climate benefits from a structure that is open to diffusion, with a higher heat storage capacity.
The “WOODCUBE” is an example of a closed material cycle in construction.
The aim is a traceable, material-specific system without hazardous waste. The unglued, solid wood boarded flooring is sealed with linseed oil, while the façade cladding is made of untreated larch wood, the insulating material of soft wood fibreboard, and all of the sealing sheets and tapes have a cellulose base.
This is an important factor, as solid construction is not particularly sparing in its use of wood as a renewable resource. At present, this does not present any problems in Germany, as more wood is produced than is consumed. However, in future, and particularly in view of carbon storage and the availability of timber as a resource, the re-use of building elements for ends other than as fuel, as is prevalent today, will become more important.
At the end of the building’s life cycle, the resources could therefore be broken down into their different types and used again as building components or materials. This form of recycling represents another strand to the resource efficiency concept, as re-using the materials reduces resource consumption in the future.
The majority of the energy required for processing timber comes from renewable primary energy (the sun).
During the implementation of the project, great emphasis was placed on maximum recycling potential. Avoiding bonding and sandwich building elements meant that all levels could be divided up again.
The “WOODCUBE’s” concept is optimised with a view to saving non-renewable resources and ensuring that the building can be recycled at the end of its life span.
All of the building components were made of solid wood if this was technically possible.
The “WOODCUBE” is the first five-storey residential building that does not use glue or fire- protective encapsulation. In addition, the building is carbon neutral: no insulating materials that require lots of energy to manufacture were used unless absolutely necessary. All of the building materials can also be disposed of singly or reused.
Resource Efficiency and Sustainability
This urban timber building, which is free of toxins within the living area, can contribute to environmentally friendly and healthy living. In addition, there is scientific evidence that solid wood has a beneficial effect on the inhabitants.
Holz100 Canada Inc.