When glass becomes too heavy, expensive or fragile to install at great heights. Cellular polycarbonate is the triumph of engineering design: by extruding plastic into a honeycomb geometry, a self-supporting panel is obtained that is simultaneously a roof, insulator and window.
Polycarbonate (PC) granules are pushed through a die that creates the continuous sheet, formed from horizontal walls connected by vertical or diagonal ribs (flutes). The historic limit of plastics in architecture is solar degradation (photo-oxidation), which makes them yellow and brittle. This is solved by UV co-extrusion: a thin layer of UV absorbers is fused directly onto the external face of the panel. This invisible shield guarantees retention of transparency and elasticity for over 10-15 years.
Dry air is trapped inside the cells (alveoli). While base panels have only 2 walls (Twin-wall), for modern nZEB roofs panels with up to 9 walls with X-bracing (40-50 mm thick) are used. These micro-chambers prevent convective movements of air inside the panel, achieving thermal transmittance (Ug) values comparable to a triple-glazed unit, but weighing only 4 kg/m² versus 60 kg/m² for glass.
Standards
European and international references applicable.
Physical properties
Usage environment
Polycarbonate has a thermal expansion coefficient 6 times higher than glass. A 6-metre sheet can lengthen by almost 2 cm in summer. Aluminium containment profiles and EPDM gaskets must be calculated to allow free sliding of the panel, otherwise it will warp and break. Always install the UV co-extruded face facing outdoors (marked with protective film).