Glazing technology has come a long way since the 1970s.
Modern aluminium offer great thermal ratings – known as ‘U’ values – and prevent heat being lost through the frame. It’s all down to a section of the frame called the ‘thermal break’ which is sandwiched between the exterior and interior aluminium parts of the frame.
The old 'fill and de-bridge' systems thermal breaks consisted of insulating polyurethane resin which was poured into a channel in the aluminium, allowed to set and then the aluminium was cut away to leave the insulating polyurethane resin holding both outside and insides halves of the aluminium frame together.
Today foamed polyurethane resin is used in various ways to offer much higher insulation values creating aluminium frames which offer very high levels of insulation.
Polyamide is a glass reinforced nylon material used for creating a thermal break strip which is both a very good insulator and thermally very stable. Modern designs of this insulator offer multi-chambered arrangements that keeps heat transfer across the frame to a minimum and offer class leading thermal efficiencies.
Passivhaus was originally a German standard of construction for the whole building structure which includes very high thermal performance windows. This form of construction, now being built in the UK, uses aluminium windows of special designs which will meet these stringent requirements.