Have you ever wondered how much it would cost to build a green version of Buckingham Palace ? The Queen's highly energy inefficient London residence is said to cost somewhere in the region of £2.2million in fuel bills each year, and is famous for being the most expensive home in the world you’ll never be able to buy but according to cost consultants, Faithful+Gould, you could build a new energy-efficient replica for £320 million. The consultants, who are a part of the Atkins engineering design group, undertook a technical assessment of the current Buckingham Palace as part of a review of famous UK monuments by the Chartered Institute of Building’s magazine, Construction Manager. It worked out that building a replica of the Palace, using the latest construction methods and materials, would take three and half years. Using a carbon calculator developed by Faithful+Gould for the Carbon Trust the team also assessed that the new Palace would emit 400 cubic tonnes of CO2 per year less than the original.

Mathew Fenner, project manager, explained: “Clearly as we were dealing with one of the UK’s most important national monuments the preservation of its heritage characteristics was the most important consideration. However the idea was also to create a technically superior building and that meant using innovative design solutions and costing in a solid project management plan.

“Although the building externally would have a traditional appearance we would include substantial levels of insulation in the walls, floors and loft space which should pay for itself in as little as two years. This was considered a key priority with the current Palace’s annual utility bill spend estimated at around £2.2 million. The insulation would cut heat loss by up to 90% compared to an un-insulated building.

“In addition, highly efficient double glazing systems would be used to replace the existing 760 traditional windows. They would be designed to replicate the original windows but would cut heat loss by half. Further carbon reductions would be achieved by installing photovoltaic panels, heat recovery systems and ground source heat pumps (subject to tube lines, escape tunnels and nuclear bunkers!) whilst grey and rainwater water harvesting could reduce potable water consumption dramatically.”

The total build cost came in at £320 million, which included the construction of 19 state rooms, 78 bedrooms, and 52 principle bedrooms. This was around ten times the original purchase, build and extension costs (incurred between 1761 and 1913) of around £33 million, in today’s terms.

Including land costs, which on the current 40 acre site could be around £440 million, the price tag would be a combined £760 million, making it the most expensive residential property in the world. The closest challenger is the Villa Leópolda, on the Cote d’Azur, which was bought by an un-named Russian oil oligarch in 2008 for £390 million.

The company has worked on other historically sensitive projects including project management of the Imperial War Museum restoration programme in London. The other UK monuments looked at by Construction Manager magazine were Stonehenge, which could be rebuilt for £815,000, and the Clifton Suspension Bridge which came with a price tag of £52 million.