Solid timber construction
For almost all building parts there are bio-based alternatives such as wood wool and cellulose for insulation, and hemp fiber and flax as biocomposite elements. But especially the use of solid timber for the structural shell – the walls, floors and the roof -, is a highly potent material. Fast-growing wood can be sawn and glued in perpendicular layers, creating large sheets with different thicknesses, aptly named cross-laminated timber (CLT). These large structural elements can be industrially manufactured into the desired shape and provided with recesses for windows and pipes through CNC milling. These elements are then assembled “dry” at the construction site. This construction method is still in its infancy in the Netherlands, but its implementation in Austria and Germany, for example, shows the possibilities for faster construction speed, lower construction costs and better working conditions for construction workers. In addition, solid wood construction has a tactile quality and promotes a pleasant indoor climate. By making solid wooden elements modular, they can also be easily replaced or adjusted, which increases the flexibility of use. When a CLT building is no longer adequate, it can be dismantled relatively easily and its modular elements can be reused and reintegrated in a new building. If the wooden elements can no longer be re-implemented, they can be recycled into low-grade wood products such as veneer, chipboard and insulation material.
Where then do we get all that wood? The Netherlands has a total of 365,000 hectares of forest, more than half of which originated as production forest used for firewood and previously in timbering mine tunnels. 225,000 hectares of Dutch forests are now protected nature areas. The remaining 140,000 hectares of forest can be used for the sustainable production of wood, as is often the case in Scandinavia. This means that trees are harvested in a limited and selective way and replaced by young specimens of the same or different species. This yields an average wood harvest of 8m3 per hectare per year, with poplars even up to 15m3 per hectare per year. This amounts to an annual production of 1.12 million m3 of wood. By diversifying the size and type of forest plantations, we add ecological, landscape and recreational value the often monotonous forests. This also benefits soil life that suffers from nitrogen emissions from traffic, the bio-industry and (conventional) construction.
An average of 50 m3 of wood is required for the construction of a home. That means that we can make 22,400 homes from Dutch wood every year and will require 45 years for the realization of 1 million “home-grown” homes. In other words: 60 homes per day “grow” in the Dutch forests. If we want to speed up production, or use the available wood for other purposes, we can import wood or plant more forests. Higher demand for wood therefore does not lead to clearing, but to more and better forests! Adding value to forestry is also an incentive for parts of the Netherlands that suffer from poor soil quality, low spatial quality and/or a declining agricultural economy. Perhaps we may even live in these new forests. Building with wood could therefore make the Netherlands more beautiful!