So much of what is in our homes these days is factory-made — toasters, furniture, toys — but not the homes themselves.

Most are still built on-site, as opposed to being prefabricated and trucked in. That doesn't make sense, says Sheri Koones, author of four books on prefab housing, including the new "Prefabulous and Almost Off the Grid: Your Path to Building an Energy-Efficient Home" (Abrams).

"Would you want your car to be built in your driveway?" says Koones, of Greenwich, Conn. "Of course you wouldn't. You want your car made in a climate-controlled factory by skilled professionals on an assembly line. Wouldn't you want the same thing for your home?"

Prefab housing, a concept that's been around at least since Sears and other companies introduced mail-order kits in the early 1900s, generally refers to factory-built modular and panelized housing. They are built to the same code as traditionally built homes, with additional structural requirements to make sure they withstand being transported. Depending on the home's size, multiple pieces (or modules) are delivered to a site and secured together onto the foundation in a matter of hours.

Prefab homes are typically 60 per cent to 90 per cent complete at the time of delivery, but often require an additional two or three weeks for finishing touches.

By contrast, mobile homes, which carry much of the stigma against prefabricated housing, are built to a more lenient federal code, arrive on their own wheels, depreciate quickly and are not generally zoned for urban use.

Because modular prefab homes are indistinguishable from site-built homes, they have become increasingly popular, pushed by the growing interest in green building.

"Prefab homes are much more efficient and environmentally friendly. There is so much less waste in the manufacturing process. Any excess materials can be recycled into other homes or sent back to the manufacturer instead of ending up in a dumpster," Koones says. "Because the materials aren't exposed to the elements, prefab houses avoid problems with mould, rot and bacteria... ."

She also cites worker health and safety as a benefit to building homes off-site. "Prefab construction professionals can work year-round, indoors, without being exposed to the elements."

Still, some consumers remain unsure of what a green home built off-site would entail.

Greenfab, a Seattle company, recently used a newly built prefab home as a teaching tool. After producing the first platinum LEED-certified prefab home in Washington State, Greenfab opened the modern house to the public for three months. School groups, builders, buyers and non-profit groups toured it.

"People in the neighbourhood just saw a foundation in the morning, and came home to find a completed house," says Johnny Hartsfield, founder and president of Greenfab. "Our main goal as a company is to educate the public on the benefits of green and prefab. "

He also lists cost as a reason to go prefab. Since the homes are pre-designed, he says, there are no architect fees, time delays or cost overruns.

"Site building is loud and stressful," Hartsfield says. "We want to make building your home more exciting and fun — we don't want you to hate it or get divorced over it."

Prefab homes can be customized. Some companies offer environmental upgrades beyond standards such as low-VOC paint and efficient appliances.

"We can install the foundation for water collection and solar adaptability in our homes," Hartsfield says. "Even if they don't have the money to set up a full solar collection system, we can build their home with the infrastructure to do that down the line."

Of course, consumers still tend to choose homes based on gut reactions, emotional connections and personal taste.

"If houses aren't attractive, no one is going to want to build an efficient house," says Koones. "One of the misconceptions about prefab is that they're all modern, and not everyone likes modern. The truth is, most of the prefab being built in this country is actually traditional."

Brooklyn, N.Y.-based New World Home, one of the builders featured in Koones' book, builds traditionally styled prefab homes across the Northeast. Founding partners Mark Jupiter and Tyler Schmetterer built on-site homes until 2006, when they decided to produce prefab green homes for the masses.

"I love chunky timber-framed houses," say Jupiter. "I wanted to make homes that fit in the neighbourhood, that conjure good feelings and are anchored in history."

He cites one project in which his prefab home was the first new construction in its neighbourhood in 100 years. The neighbours were wary, but came around when they saw the finished home, he says.

And after building a model home in the upscale Hamptons, on Long Island, N.Y., New World Home won over the neighbourhood and produced five more homes there, Jupiter says.

"Modern is hard to relate to for some people," he says. "Our stylings are based on a rich architectural history. esthetically, they look like they've been around for 100 years, but they perform like they're 30 years in the future."