The main building at City College Norwich is being revamped to make it more comfortable for students.
Work on the Norwich Building will begin in the coming weeks.
The improvements, which meet planning guidelines to remain in keeping with the building's original 1930s design, will see the replacement of about 370 windows and the roof.
They need to be replaced to ensure a comfortable and suitable learning environment for the large number of the college's 14,000 students who use it.
The replacement of the windows and roof will remove draughts, reduce noise and improve the energy efficiency of the building. It is estimated that, with improved insulation, the finished works will lead to annual savings on the college's energy and maintenance bills of about £50,000.
The work has been made possible after the college successfully bid for a £1.14m grant from the Skills Funding Agency to upgrade the Norwich Building and put in place a new pre-fabricated building for training in construction and the built environment (CBE).
The original construction of the Norwich Building took over a decade to complete. Building work began in 1939 as part of the relocation of the technical school from St George's Street to Ipswich Road, and much of the steelwork was in place when the outbreak of the second world war halted its construction.
Work on the main building was not officially completed until December 1949, with the south and north wings following in 1951 and 1953.
It was only in October 1953 that the whole of the Norwich Building was officially opened by the Lord Lieutenant of Norfolk, Sir Edmund Bacon.
The frontage of the Norwich Building is 50ft longer than that of Norwich City Hall, and it was also notable for being the first new college building of its kind since the end of the war and for its under-floor heating.
Corrienne Peasgood, City College Norwich principal, said: 'The improvement works we are now undertaking will ensure that this iconic building, at the very heart of the college, will provide a modern, comfortable and more energy-efficient learning environment for many years to come.'
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