trees became the trend with special-purpose buildings built to protect the tasty, but delicate fruit. Orangeries, as they came to be called were typically enclosed structures built with wood, brick or stone with tall vertical windows on the south walls. The citrus trees were typically in huge pots or tubs, and wheeled outside for the summer months, as at the Gardens of Versailles. Use of these rooms expanded socially and practically, being used to entertain and to host a wider variety of plants. The term greenhouse came to describe the rooms and conservatories for tender plants. In the 18th century a Dutch scientist pioneered the use of sloping glass to bring in more light for the plants than the tall, glass side walls of orangeries. The 19th century was the golden age of conservatory building, primarily in England. English conservatories were the product of English love of gardening and new technology in glass and heating technology. Many of the magnificent public conservatories, built of iron and glass, are the result of this era. Kew Gardens in London is an example of a large greenhouse used for growing tender and rare plants, or, less often, for birds and rare animals – sometimes with the plants and animals living together. Other examples include the Great Palm House at Kew Gardens that was built in 1844, built by Decimus Burton and the Crystal Palace, built for London's Great Exhibition of 1851 by Sir Joseph Paxton. The widespread construction of UK conservatories came to a halt with the onset of World War II. While the advent of insulated glass in the 1950s and 1960s saw the development of simple sunroom structures, it was not until the 1970s that creative architects and builders began to recreate the Victorian styling of 19th-century English conservatories in smaller domestic versions using insulated glass. In contemporary construction, a conservatory differs from an orangery in having more than 75% of its roof surface made from glass. Frame and roof materials include aluminium, PVCu and timber. A conservatory by definition must have more than 50% of its wall surface glazed. Contemporary conservatories use a number of technologies to ensure glass is as energy efficient as possible, ensuring it lets in the maximum light possible while maintaining a steady temperature throughout summer and winter. Technologies include argon-impregnated glass, easy clean coatings, heat reflective film, thermal ribbons or thermal breaks – hollow sections