In its third month of construction, the floor plan has emerged at David Horobin’s green house project in Napa. Rooms are starting to take shape and workers are installing the second floor of the innovative house into which Horobin, an Oxford-trained architect, is incorporating years of experience as a green-living advocate.

Interior walls are going up, but instead of the traditional wood frames, these are all steel. Steel is a practical choice today, said Horobin, who has designed the house for his family. Not only is the quality of available wood unreliable, but with steel frames, it’s only a question of providing the manufacturers with measurements and having a truck deliver the assembled walls. Workers can install them in a matter of hours.

“The labor savings are huge,” said Lynn Horobin, who, like her husband, is often on site to survey the construction of her dream home.

“They’re delivered the perfect size and height,” Horobin said. “About three-quarters were installed in one day, whereas a traditional frame would have taken about a week. With the cost savings in labor, it works out to be less expensive.”

As the Horobins led a tour into the house, however, the most striking thing was how cool it was. As yet there are no windows, no roof, no doors on this house but on a sweltering August afternoon, it was pleasantly comfortable.

In part it comes from the building materials Horobin has chosen. The concrete-filled foam blocks, some manufactured by ARXX, and some from Horobin’s own design, are nearly a foot thick and create the same insular coolness one feels walking into an old stone building in the valley.

Also at play here are the details of Horobin’s design, carefully conceived to take into consideration the contributions of nature —cross breezes and the path of the sun. 

The hillside lot in Alta Heights Horobin found is a challenging one, which is most likely why it’s remained undeveloped as houses have grown up around it. It slopes down on the east side of the steep Montecito Boulevard, and is, like most of that area, solid rock. But it looks south and south east to views of Coombsville and beyond.

“The views were a major consideration in the way the house is laid out,” Horobin explained.  He wanted to capture the views without obliterating those of his neighbor, whose house is higher on the hill.

“We didn’t want to come in and upset everyone,” Lynn Horobin said.

Instead the two-story, four bedroom house seems to move gradually down the hillside. On the ground level is the living room, along with two bedrooms for the Horobin’s teenage boys and an adjoining bathroom. These bedrooms face east. “I don’t know about your teen-agers, but ours need every ounce of sun in the morning they can get to wake up,” said David Horobin.

 Upstairs is a master suite and a second bedroom, which, although they’ll have their own views, will be just below the neighbor’s viewline. “The idea was to bring the second story down as low as possible,” Horobin said.

The kitchen, west of the living room, and slightly raised above it, has a curved window looking south, for exposure to the sun as it moves across the sky, something Lynn Horobin especially likes. “I wanted the window, but not to have that feeling of the sun beating in,” she said.

Cross breezes also came into play as Horobin designed the house. He drew a diagram showing how breezes will come in from windows on the north and south, but hot air rising will be able to escape via skylights, which will be remote-controlled. Green?

“Absolutely,” said Horobin. “There’s nothing ungreen about remote control. One problem with traditional hand-operated skylights is that people get tired of opening them.”

Taking all the details of exposure and materials into consideration adds up to a house that won’t require air conditioning.

“Basically the considerations are comfort and energy, which can be contradictory,” Horobin said, “but because the design is so efficient, the thermal mass of the concrete tempers the internal environment of the home.”

“And I’d rather have breezes than air conditioning,” Lynn Horobin said.