The most widely used methods of insulating rooflights is using multiple layers of materials with high-transparency. This approach is reasonably effective for uses where moderately improved U-values are required, and a common technique would be use to use multi-wall or structured polycarbonate sheet.
Still air pockets are created and conduction is minimised by using thin walled sections to inter-connect the walls or layers within the polycarbonate; for each layer is added, there is a penalty in terms of light-transmission due to the cumulative effect of the reflectance of light at each and every layer. As the number of layers increase, so does the the absortion into the increasing mass within the rooflight cavity and the greater the re-radiation of heat through the rooflight as a secondary component of solar gain.
Zenon Insulator™ core
To overcome the problem of achieving environmentally friendly, low U-value
rooflights without significantly compromising the light transmission, Hambleside Danelaw developed the unique Zenon Insulator™ core system.
Made from cellulose acetate, a recycled wood pulp product and compostable at the end of its service, it provides much improved U-values without the penalties of creating multiple layers within the rooflight. It achieves this by trapping and containing the air in small pockets within the rooflight cavity thus significantly inhibiting the convection currents that carry the heat through the rooflight panels to the outside air.
The honeycomb Zenon Insulator core comprises a lightweight, transparent cell structure that is perpendicular
to the plane of the rooflight. This requires only a single thin clear film layer to encapsulate the air pockets and has
minimal interference with the light transmission. The light entering the cell structure is channelled directly, or by
reflectance, into the building creating a better, wider spread of diffused light irrespective of the angle of incidence of the light, and at the same time, minimises the absorptance and re-radiation of the light energy as heat energy.
The standard thicknesses for insulation layers when using simple structured polycarbonate inserts for both site-assembled rooflight applications for built-up cladding systems, or composite panel rooflights for use with composite cladding systems, are 4mm twin-wall or 10mm four-wall panels.
Zenon Insulator is available for both site assembled rooflights or composite panel rooflights. There are three standard thicknesses available, 20mm, 40mm and 80mm, depending upon thermal performance requirements. Unlike increasing the layers of polycarbonate, the high light transmission property of Zenon Insulator enables it to be used in multi-layer
combinations where very low rooflight U-values are required without compromising light transmission into the building. The thermal properties of any rooflight insulation layer should always be considered in conjunction with the U-value of the rooflight outer and liner sheets, and the type of assembly in which they are to be incorporated.