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the power of hybrid

Wood is hot. By now some sort of belief seems to have emerged that more wood is automatically better. The popularity of wood is justified in the pursuit of a more sustainable and healthier world. After all, wood is unique because it is one of the few building materials that is renewable and absorbs CO2 during growth. Many people also find the appearance of wood warm and pleasant. However, there seems to be a blind spot when it comes to efficient use of materials. A lot of wood is needed for solid constructions, while reducing the use of materials is one of the first pillars of sustainability.

Our office is located in an early twentieth-century hall of the Delft Technical University. The roof consists of a wooden deck and purlins. Its wide span is supported by five slender and lightweight steel Polonceau frames. The hybrid roof design by former Government Architect Jan Vrijman is a miracle of material minimization, in which wood and steel both do what they do best.

Given the high demands on fire safety, vibration and sound insulation, even the most ambitiously labelled wooden high-rise buildings actually result in such a hybrid. For a building that is both technically and economically feasible, wood simply needs a steel or concrete backing. But there is nothing wrong with that: a hybrid still requires substantially less steel or concrete and ultimately also substantially less wood. Hybrid constructions also lead to much greater flexibility and thus functional durability: all-wood often requires fine-meshed constructions with enormous trusses and columns as well as load-bearing CLT slabs. This results in rigid typologies similar to those of traditional concrete-cast structures.

Also, there is much to be gained on connections. Today, wood is often literally clumped together into inseparable packages by means of contaminating adhesives. This is environmentally unfriendly, but also stands in the way of reuse and adaptability. The same goes for the appliance in hybrid setups. A focus on flexibility and detachability of wooden structures seems like a good resolution for the new year.

Ronald Schleurholts, architect partner cepezed

Cobouw, December 17th 2020