New ideas for home design often come from the workplace. The home Karen Daroff and Jim Rappoport designed and built for themselves incorporates commercial ideas into comfortable living quarters.As principals in Daroff Design Inc. in Philadelphia, they create interiors for offices, hospitals and hotels. They decided to cooperate on their home, using the theories, techniques and materials they generally apply on the job. The result is rather severe, a pure white temple of modern architecture set on a wooded acre next to Fairmount Park in Philadelphia.In it, they used materials that perform well in commercial spaces. The windows, for instance, are composed of standard-size insulated reflective glass, which keeps the rooms cooler in summer and warmer in winter. The white marble tiles in the bathroom, says Daroff, "make you feel as though you're in a Milanese hotel.""We installed all the necessary smoke detectors and security devices," she said. "Edges are rounded, not sharp. Materials we are using don't contribute to flame-spread and toxicity." Advertisement They say that their expertise helped keep costs for the 4,500-square-foot building to about $100 a square foot; the usual cost for custom building is $180.They chose ready-made components and limited the amount of on-site work. For example, pocket doors (these slide into the wall)--can be expensive to install, but the couple selected a door size available in cut form, which reduced the cost. The storage walls have factory-built cabinetry, which reduced the amount of custom cabinet work.Rappoport considered the placement of the trees on the lot in deciding where to situate the house. In summer, the shade from them cools the structure, which has many windows. In winter, the sun will provide solar heat.All of the rooms on the first floor open onto the main living space at the center of the house, where the ceiling is a pyramid-shaped skylight. Rappoport calls the idea "interpenetrating spaces." When you are in any one room, you can see the other rooms beyond, which creates a sense of spaciousness. Each can be closed off when desired using a pocket door. Advertisement The couple bought the sleek laminate-surface kitchen cabinets, the granite for the countertops, some of the storage furniture, and tiles and marble directly from the manufacturers in Italy. All were shipped to Philadelphia in a single container.They paid $55,000 for those components, about one-third what the U.S. retail price would be, Rappoport said. And Rappoport made it all sound easy: "When the container arrived at the seaport here, I hired a guy with a truck to deliver the container to our site. It cost $250."As his own contractor, Rappoport was on the site daily at 7 a.m. He hired the subcontractors himself, and he made sure the materials were there when they were needed. Scheduling, he says, is usually the biggest problem on construction jobs."Workers leave the site when the materials they need are not right on hand," he says. "Once they leave, it's very difficult to get them back, and the time needed to complete the building starts escalating."If trust is an essential part of marriage, Daroff and Rappoport are ahead of the game. This past spring, Daroff was planning the couple's wedding, which was to be in mid-June in a house that was then just a shell. Building a house together is not usually recommended as a good introduction to marriage. But, Daroff says, "overall, it was a positive experience. We both worked hard to incorporate each other's ideas. At first, it was difficult. We are both very opinionated."Normally, client demands dictate design choices."We had no clients, just ourselves," she said. "But the site had a lot to do with the decisions we made. And our strengths are complementary--Jim's in conceptualizing, planning and scheduling. I have greater strength in details of finish materials. Luckily, we happen to enjoy the same preferences in terms of style."Although the house was several months away from being ready to live in, Daroff and Rappoport were married there in June. Advertisement Distributed by AP Newsfeatures.