Hampton Court Palace, the spectacular home of Henry VIII, will be the main focus of the scheme to improve the energy efficiency of three sites managed by the Historic Royal Palaces charity.
Work will also be undertaken at the Tower of London to insulate the Queen's House, built in 1530 for Henry VIII's second wife Anne Boleyn, and at Kensington Palace, where Queen Anne's early 18th century orangery will be insulated.
The scheme, which will see about 11,000 rolls of insulation installed by British Gas and insulation company Rockwool, is expected to cut 130,000 in total from the palaces' gas bills and reduce carbon emissions by 850 tonnes over the lifetime of the insulation.
The energy efficiency programme will put loft insulation into more than 4,500 square metres of the roofs of the three palaces – the equivalent of 100 average semi-detached houses.
Almost 80 per cent of the work will be focused on Hampton Court Palace, where 3,500 metres of the palace will be insulated.
The palaces are thought to be the oldest former royal residences to be insulated and will need expertise to install the insulation in rafters that are more than 500 years old, the scheme's organisers said.
Michael Day, chief executive of Historic Royal Palaces, said: "These great palaces have stood the test of time over hundreds of years. Today we must make sure they are suitable for a new low carbon future.
"This project, generously supported by British Gas and Rockwool, will not only make some of Britain's most important buildings more environmentally sound, but will also deliver significant and ongoing savings to our energy bills which is invaluable to us as a self-funded charity.
"Protecting the environment and making savings to charitable expenditure will further enable us to ensure these palaces and their wonderful stories will be here for future generations to enjoy."
Jon Kimber, managing director of British Gas New Energy, said: "Whether it's a 500-year-old royal palace or a suburban semi-detached house, installing insulation makes financial and environmental sense."