การฟัง TOEFL

🎧 บทถอดเสียง

Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about urban heat islands, and specifically how city design can mitigate their effects. One effective strategy is increasing the albedo of rooftops by using reflective materials. When sunlight hits a conventional dark roof, most of the energy is absorbed and then re-radiated as heat. A white or reflective roof, in contrast, reflects a significant portion of that solar radiation back into the atmosphere. This can lower the roof's surface temperature by up to 30 degrees Celsius on a hot day, which in turn reduces the heat transferred into the building below. As a result, air conditioning demand drops, saving energy and reducing greenhouse gas emissions. Another approach is green roofs, where vegetation is planted on the rooftop. These roofs provide insulation, absorb rainwater, and through evapotranspiration, they cool the surrounding air. While green roofs offer multiple benefits, they require more structural support and maintenance. Reflective roofs, however, are cheaper and easier to install, making them a practical first step for many cities.