Architects, environmentalists and some forward-thinking builders embrace prefab construction. But despite having been around for decades, it made up just 2 percent of new single-family houses in 2016, according to the U.S. Census Bureau.

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Design magazines love them. So do movie stars and environmental activists. New technology, including the use of robots in factories, makes them even easier to build.

So why are advocates of prefab houses still talking about “disrupting” the home-building industry?

Architects, environmentalists and some forward-thinking builders embrace prefab construction — whose products run the gamut from affordable manufactured homes to sleek tiny houses with ultramodern finishes to contemporary mansions — as the way every home should be built in the future, says Sheri Koones, author of “Prefabulous + Almost Off the Grid” and other books about prefab houses. But despite having been around for decades, prefab or modular homes made up just 2 percent of new single-family houses in 2016, according to the U.S. Census Bureau.

Prefab construction gained traction in the 1970s when builders and architects recognized they could save on build time and labor costs by moving the majority of the building process into a factory. Initially, says Koones, modular homes were fairly basic and boxy, but over time architects, builders and factory owners have improved their methods, and nearly anything that can be built on a homesite can now be assembled first in a factory.

While prefab houses can cost less than a traditionally built home, the financial savings are not always the most compelling reason for people to choose this construction method.

“The real saving is in time,” says Brian Abramson, co-founder and director of business operations for Method Homes, a prefab factory in Seattle that works mostly on modern, custom homes. “It typically takes 50 percent less construction time to complete a prefab house.”

Building the house in a factory limits weather delays and makes the delivery date more predictable. Change orders are usually not allowed, which also speeds construction.

Fewer hours on-site translates into some saving on labor costs. Michael Winn, owner of Winn Design + Build in Falls Church, Virginia, which uses prefab construction for additions and custom-built homes, estimates that prefab construction can save as much as 15 to 20 percent compared with the cost of a traditional custom build.

The “cool” factor has also helped fuel interest. Actor and environmental activist Robert Redford is so enamored of prefab building that he has written introductions to several of Koones’ books. Design magazines and blogs regularly showcase prefab houses.

Modern-style architecture is commonly associated with modular construction simply because the clean lines and flat surfaces can be shrink-wrapped and stacked on a truck more easily than the parts of a Victorian-style home, says Mimi Hoang, co-founder and principal of nARCHITECTS in Brooklyn, designers of microunits in Manhattan that were built with modular construction.

But as long as the architect understands the guidelines of the engineering that takes place in the factory, there’s really no limit to what you can build with modular construction, says Mark Giarraputo, an architect with Studio Z Design Concepts in Bethesda, Maryland.

“You can do any style you want from traditional to Craftsman to Colonial to Tudor or contemporary,” says Giarraputo. “Prefab lends itself a little more to contemporary homes because of the clean lines, but you’re not limited to that style.”

A significant turning point for prefab homes came in 2002-03, when Dwell magazine held a competition for architects to design a $200,000 prefab house, says Ryan Smith, director of the Integrated Technology in Architecture Collaborative at the University of Utah in Salt Lake City. Suddenly, prefab houses were the epitome of cool architecture.

“Prefab construction became the holy grail of design,” says Joseph Tanney, co-founder of Resolution: 4 Architecture in New York City, winner of the 2002 Dwell magazine competition. “The idea was that it would be the answer for modern, affordable, mass-produced housing. We’ve seen far fewer prefab factories than what we expected.”

Some of the buzz around prefab architecture continues, says Tanney, enticing architects to create renderings for prefab houses and occasionally build one. More than half of the 15 to 20 houses Resolution builds annually are prefab. But the reality is that most prefab houses are more pedestrian, Tanney says: “Most modular factories are building prefab houses for communities that are naturally more traditional to attract more buyers. The excitement around modern prefab architecture is just because it’s more interesting.”

Smith says prefab housing is more common in other countries, particularly Sweden, Japan and Germany. “The difference is that they tend to be production-based, so the homes all look alike, even if they are high-end homes. The North American preference is for more customization.”

Tanney says prefab construction hasn’t changed architecture, although it’s gotten more people outside of the architecture world interested, and the quality of the buildings has improved over the past 15 years.

“I expect to see more single-family home production with prefab construction in the future,” says Smith. “But not custom, high-end prefab homes. That’s more of a novelty.”

Today, modular parts can even be constructed by robots in some factories, which addresses the current shortage of construction labor. Parts are put together on-site in a few weeks rather than months.

“Prefab construction is the best-kept secret in America,” says Koones. “Every house should be built this way, but most builders want to build the way they always have. They can charge more money when they use traditional methods, too.”