This paper investigated the spatial delight and environmental performance of two selected apartments in the modernist buildings at Golden Lane Estate built after the 2nd World War. This estate is a Grade II listed, high density, low cost housing complex designed by three young architects: Peter Chamberlin, Geoffrey Powell and Christof Bon and it was built over a bombed site, and well embraced the post-war modern architecture ethos, environmental considerations and inclusion of social facilities and landscaped communal spaces. Two apartments in different building blocks with similar size, orientation, internal layout, use of materials and building elements were chosen for this study. However, one apartment has been refurbished with internal insulation and secondary glazing for improving the comfort conditions. Through fieldwork, which included on-site monitoring and interview of the building occupants, first-hand information on the environmental and comfort conditions inside the apartments were obtained. Through performance based theoretical analysis, the comfort conditions in the apartments and energy consumption were critically assessed. The research findings indicate that through selective enhancement of the thermal property of the building envelopes by internal insulation, introduction of secondary glazing over the original single glazed windows and the improvement on the air tightness in the apartments, the original naturally ventilated and well day-lit living environments were maintained while the overall comfort level was significantly improved. This paper presents the feasible strategies to deal with the environmental challenges in the post-war Grade II listed residential buildings in the UK.