When building houses, people used to think about not only the climate of the areas but also the building materials and the fashions for their houses. However, since electricity became more and more expensive, people began to pay much more attention to the energy they could get for their houses and the new ways they could find to protect their houses from both cold and heat.

Now, houses of an old yet new type have been widely built. In some parts of the world, people share their houses with their livestock(家禽). During cold weather, they gather their cows, goats, or other animals and keep them on the first floor of their houses. The reasons are that the animals can be protected from the cold and that they can help to heat the houses as well. The body heat given off by the animals rises to the second floor of the houses, where people live in. By sharing their houses with their livestock, people gain a source of heat.

People who live in or near cities do not usually keep livestock. However, home builders use the fact that heat rises. This natural law can be used in building houses in these areas. Instead of keeping livestock on the first floor, builders fill it with large rocks. As they are open to the sun’s rays during cold weather, these rocks take in heat. They also give off the heat, and, of course, the warm air rises into the living areas of the houses. So these houses are energy-saving.

House-building becomes a great challenge to building designers and energy engineers. They try to meet this challenge by learning from old traditions and by using modern technology. And someday in the future, people will be able to live in more energy-saving houses.

The Hotel Wake-up Call Gets Personal

Here’s a wake-up call: The hotel front desk will do one better than ringing your phone in the morning. They’ll send an actual human being to your room. Don’t worry. They won’t come in and kiss you good morning. 【小题1】

Never mind that most travelers nowadays have smart phones with built-in alarm clocks. 【小题2】 Here are some examples. At the Wolcott Hotel, if a wake-up call is unanswered, they will send an employee to your door. At Las Ventanas al Paraiso, an employee shows up at your room to wake you up with tea, coffee and breakfast bread. At the Mandarin Oriental, a person rather than an automated system will call to wake you up. 【小题3】

Hotels have always taken the wake-up call seriously. 【小题4】 If you don’t get your call within five minutes of the requested time, you won’t have to pay for your room. Travelers, too, still want to have an option of a wake-up call. A study of 285 guests at Crown Plaza found that 53% considered a wake-up call very important.

【小题5】 It used to be that a person would call you. Then in the late 1980s, hotels turned to automated systems. Then all you’d get was a ring and silence. In the ever-competitive race for loyal customers, however, many hotels are now getting creative with the wake-up call Some hotels even have recordings of celebrity voices. And more hotels will go back to the old in-person system of wake up calls.

Why build a house when you can print one instead?Startups（初创企业）around the world are now using 3 D printing technology for home construction.They say it's faster, cheaper and more sustainable than traditional methods.Printing houses can also save huge amounts of wood（垃圾堆）.

Currently, 3 D printing systems can equal the work output of 10 to 20 workers in five or six different trades, said Jason Ballard, a 3 D printing construction startup, according to AP News.The machines can work 24 hours a day as well

So how do these 3 D printers "print" a house anyway?Machines deposit（使沉积）thin layers of material — such as concrete（混凝土）, metal and plastic — until the three﹣dimensional house is built from the ground up.And a house can be completed within 120 hours, according to CNN.

Ballard said that 3 D printing was like the most powerful automation of all the automations we could discover.This powerful automation has the potential to prevent rising prices in the housing market, homelessness and overcrowding.But the technology behind 3 D printing houses is still in its early stages of development.For example, ICON alone has only printed 24 houses in the US and Mexico.But（梦想家）from dreaming of larger applications of this technology.

"With the 3 D printed home, we're now setting the tone for the future：the rapid realization of affordable homes with control over the shape of your own house, " said Yasin Torunoglu（市议员）for housing in the community of the Netherlands' first 3 D printed house.