Plug and Play

PLUMBING, ELECTRICAL, AND MECHANICAL systems are among the most expensive and labor-intensive parts of a house. Philadelphia architect Michael Rosen hopes to change that by consolidating these systems into one central wall, then designing the rest of the house around it—an approach that turns traditional design on its head.

The first builder to try Rosen's “CoreWall” concept saved enough time and money that he wants to build a series of new homes around it. And while that wall was stick-built, Rosen is getting ready to introduce a prefabricated version that the builder can plug into each new home while it's under construction.

Rosen says that he can design any home around CoreWall, but the concept is ideally suited for production housing. In fact, it grew out of his work with national production builders. “Most of my business is designing prototypes for big builders, and I'm always looking for ways to make those prototypes more efficient,” he says. Since the most complex parts of the home are the utilities, including the kitchen and bath areas, he decided that he would get the most efficiency by focusing his efforts there.

He explored modular construction and even talked with companies that would make kitchen and bath modules, then truck them to the site, where the builder could incorporate them into an otherwise conventionally built home. But these companies wouldn't do enough customization to make the strategy viable.

Then the proverbial light bulb went off. “I got the idea of collapsing all the complexity into one wall, then building the house around that wall.” He calls CoreWall “the home's engine,” because it houses all of the utilities that drive the home.

The concept goes way beyond stacking baths. “A good architect will already try to centralize mechanicals and to stack bathrooms,” says Rosen. “Putting everything in one physical wall takes that process to an extreme. This has never been done. No one has taken the approach of starting with one wall, and then having that wall drive the entire home design.” Realizing the benefits of this approach means grouping all of the home's wet areas—baths, kitchens, laundry rooms—around the CoreWall. “It's a more efficient way to build in that there's only one wall with any plumbing and mechanical systems,” he says.

Developing the concept was one thing. Rosen still had to find a builder who would try it on an actual home. The break came while working with Herron Hill Construction of Kennett Square, Pa., on a senior housing community that included a number of single-family homes with small profit margins. “The builder was nearing the end of project, where the lots were less and less desirable to buyers,” recalls Rosen. “To keep their margins, they needed a way to drive down the price of their standard housing product.”

PRODUCT PLACEMENT: Herron Hill's next homes will use a prefabricated CoreWall that is shipped to the site and plugged into the home.

Rosen saw it as a perfect opportunity to try CoreWall in the real world, but the builder wanted to stick-build the concept before committing to the prefab wall. And while Herron Hill immediately saw the potential for savings, it knew that making it work would mean getting subcontractors on board. “We had to explain to each sub what they would be responsible for, how the wall was going to work, and how it would affect what they would be doing at trim-out,” says Herron Hill vice president Jim Gannon.

TESTING THE CONCEPT: This single-family home that Michael Rosen designed for Herron Hill Construction in Kennett Square, Pa., was the first to use the new CoreWall design. All of the home's utilities have been centralized in two walls, indicated in red in the drawings shown here. All wet areas have been grouped around those walls.

So Gannon arranged a site meeting between his subcontractors and Rosen. He was glad to find that the subs also grasped the concept and that they liked the simplicity of its design and implementation. “We weren't asking them to do anything they had never done,” Gannon says. “We were just taking a couple of steps away from them during rough-in.” Of course, taking away those steps meant that his subs would make less money per house, but they were busy enough that they appreciated being able to finish a house in less time. “It's not taking anything out of their pockets,” he says.

And Gannon says that CoreWall has delivered on its promise of savings: He figures it has cut the time required to rough-in the home's plumbing, electrical, and HVAC in half, from four days down to two days. “Being able to centrally locate the utilities into one wall has really driven down our materials costs,” says Gannon. “It also reduced the time required to complete the rough-in and the finish.” And he says that customers liked it “because it was a good, efficient design.”

Gannon is now planning a series of homes that will use the prefabricated CoreWall. The prefab version will consist of a SIP that's laser cut to accept all of the home's utility connections and mechanical hubs. These can go beyond the electrical panel and water connections to include a structured wiring box, a home monitoring and security system, as well as the HVAC supply and return ducts. Just dropping the wall into place will complete most of the utility rough-in. Proprietary couplings will let workers easily connect standard plumbing fixtures and mechanical components to the connections in the wall. Because the wall eliminates the need for plumbers or HVAC workers during rough-in, Rosen believes it will reduce total construction costs by 15 percent.

These kinds of efficiency savings are becoming crucial, as ever-more-complex systems drive up the cost of housing. “Traditionally, you designed a home to fit the needs of the homeowner, then added the technology,” says Rosen. “What we did with CoreWall was ask the question, ‘What if you designed a house that revolved around technology?' ”

Gannon is betting that the answer will be a more profitable builder and a happier customer. “The stick-built CoreWall worked very well. I'm confident that the prefabricated one will work just as well,” he says. “There's no reason to go back the old way of doing things.”

Charles Wardell is a freelance writer based in Vineyard Haven, Mass.

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