HiLo is a research and innovation unit for lightweight construction and smart and adaptive building systems. It is a two-storey apartment that will be built in 2018 on NEST, EMPA’s modular research building in Dübendorf, Switzerland. The roof of the unit is a double-layered, doubly curved, carbon-fibre-reinforced concrete shell structure with integrated hydronic heating and cooling, and a thin-film photovoltaic system on top. With a total height of 7 metres, the roof covers an area of 120 square metres and has a total surface area of 160 square metres. A full-scale prototype of the bottom layer of the concrete roof was built in the Robotic Fabrication Lab of the Institute of Technology in Architecture at ETH Zürich as a dress rehearsal for its innovative construction system.
The base of the system is composed of reusable scaffolding elements that support a set of timber edge beams. A cable net spans between the beams and the lower supports, and a fabric on top serves as shuttering for the sprayed concrete. The cable net comprises of custom-cut steel cables connected by rings and brackets, and is calculated such that it deflects under the weight of the wet concrete into the correct final geometry, which it then supports until the shell has cured. To achieve this, the cable net must be precisely tensioned at the right angle from specific anchor points in the CNC-milled edge beams.