Buổi 12: Reading – Summary completion & diagram labelling (làm mát công trình không cần điều hòa)

Learning from old buildings: keeping cool without machines

(Bài đọc tự viết; nội dung ở mức phổ thông, có rào đón.)

A For most of human history, people in hot climates kept their homes bearable without electricity. As air conditioning spread during the twentieth century, many of these techniques were abandoned, often dismissed as old-fashioned. Today they are being studied again, partly because cooling machines consume large amounts of energy and partly because, during power cuts, buildings that depend entirely on them can quickly become dangerous.

B The simplest of these techniques relies on what engineers call thermal mass. Thick walls of stone, brick or earth absorb heat slowly during the day, so that the rooms behind them stay cooler than the air outside. At night, when temperatures fall, the walls gradually release the stored heat. This works best in places where days are hot but nights are cool; in climates that remain humid and warm around the clock, heavy walls may simply hold on to heat and make sleeping more uncomfortable.

C That limitation explains why buildings in humid regions often took a different approach, emphasising ventilation over mass. Raised floors, high ceilings and windows placed on opposite sides of a room allow air to move freely, carrying heat away from the body. Light-coloured, reflective roofs, meanwhile, reduce the amount of solar energy that enters the building in the first place.

D Perhaps the most ingenious device is the wind catcher, a tower found in parts of the Middle East and elsewhere. Openings at the top of the tower face the prevailing wind and direct it down into the house. In some designs, the descending air then passes over a pool of water in the basement; as some of the water evaporates, the air becomes noticeably cooler before entering the living rooms. The warm air inside, now displaced, escapes through the courtyard at the centre of the house, which is itself shaded for much of the day.

E None of this suggests that machines can or should be abandoned. In extreme heat, and for vulnerable people, mechanical cooling may save lives. The lesson is rather that design and technology work best together. A building that uses mass, shade and ventilation wisely needs far less mechanical help, and older buildings can sometimes be retrofitted with reflective roofs or improved ventilation at relatively modest cost.