The FAKRO FTT U8 Thermo® quadruple-glazed roof window has a U-value of 0.58 W/m2K, making it the most energy-efficient standard product currently available and ideal for energy-efficient buildings such as those designed to Passivhaus standards. It is supplied complete with external thermal flashing, vapour permeable underlay collar and airtight interior flashing.

The FTT U8 has a raised pivot point situated in the top third of the frame for added user convenience. Its glazing unit is set in a specially designed sash frame that reduces potential for thermal bridging and provides a 38 dB acoustic performance. A quadruple-seal system uses flexible thermoplastic elastomer (TPE) that does not harden.

Other FTT products include the triple-glazed FTT U6, the 52mm thick glazing unit of which can also be adapted for use with thermal flashing. Its U-value is 0.81 W/m2K while the triple-glazed U5 is 0.94.