Framing of unitized curtain walls is dimensioned to carry wind load without taking advantage of potential composite contribution of glass. Subsequently, it is unnecessarily deep, occupying valuable space, and protrudes to the inside, causing visual disruption. Moreover, it is generally made of high thermal conductivity metal alloys, contributing to substantial thermal transmission at joints. An innovative frame-integrated unitised curtain wall has been developed that, compared to conventional systems, reduces structural depth significantly, allows an inside flush finish and reduces thermal transmission at joints. The idea is to adhesively bond a Glass Fibre Reinforced Polymer (GFRP) frame to the edge of the Insulated Glass Unit (IGU), thereby achieving low thermal transmittance and composite structural behaviour. The frame is to fit within the glazing cavity depth. This paper provides a description of the proposed system and assesses its thermal transmittance and risk of condensation through comparative analytical and numerical thermal analysis with a conventional system taken as reference.