Warblington School, run by Hampshire County Council, is one of the last surviving multi-storey BAC II aluminium system buildings and was designed and built after the second world war. Heritage England listed the original buildings Grade II in 2019 and the design project brief was to improve the heat loss in the existing toughened glass and restore the aluminium frames during the process. One of the main problems for the school was the green house effect in summer, with classrooms heating up and the cold in winter. The single glazed school had a U value of around 5.8 W/m²K, so glass improvement was a necessity. We suggested toughened vacuum insulated glass units with a low solar heat gain co-efficient to counteract the green house effect and this was approved by HCC.