PRO TEC Xframe has the best energy balance because it is generating more energy during the year than it is losing.
In residential properties it is the intention to encourage the free solar heating into the building and keep it there. PRO TEC Xframe is setting new standards for modern windows with an indoor temperature of more than 15¡C, where the outdoor and indoor temperatures are 0¡C and 20¡C, respectively Ð much better than the 9,3¡C which have been set down in the building regulations.
Please note that these product properties are not a replacement for the manufacturer's literature and it is always recommended that Inwido UK is consulted before specifying.