Using BIM to design a ‘Net Zero’ home

Using BIM to design a ‘Net Zero’ home
Courtesy of John Zona III

In nature, nothing is perfectly square, and organisms orient themselves by the sun. Both truths explain the fresh design of the “net zero” Zona home.

The Jacksonville, Florida, residence, designed using ArchiCAD software from GRAPHISOFT, the personal home of by architect John Zona III and his wife. It features a main residence and guest cottage/studio, both with American football-shaped footprints to minimize the considerable cooling demands of homes in Southern climes.

The long edges of the home and studio face the south and north. A northern exposure is naturally cool, and deep porches on the south side shade windows from any direct sunlight. The points of the football face the higher-intensity east and west, offering very little surface area to absorb heat.

Courtesy of John Zona III

It’s nothing like the original plan. “I started out with a nice design for a typical architects’ home,” says Zona. “As I was about to file for permits, I found myself at an American Institute of Architects seminar on sustainable design. Although I’ve always loved sustainable design, I kind of woke up and said, ‘What the heck am I doing? I have a golden opportunity to build one last home, and I’m building the proverbial architect’s house like everybody else? Why am I doing this?’ So I stepped out of the box, as we have always done for our clients. I tore up the plans and started sketching anew, literally on the back of a napkin.”

He drew a football shape. Then another. And went on from there.

first floor plan
second floor plan

He added a third building, a greenhouse in the clearing, which plays a key role in the home’s net zero status. As a net zero home, the Zona property consumes no more power than it produces. The greenhouse carries solar photovoltaic panels that can produce 6.5 kwH. A special electric meter enables the compound to sell electricity back to the grid during sunny spells and borrow from the grid when sunlight is scarce. “We could go completely off the grid,” Zona explains, “but batteries are not yet efficient enough to economically store solar-based electricity.”

Zona added a geothermal cooling system that consumes less than half the energy of even the most efficient conventional air conditioning. It draws 70 degree F water from an aquifer 300 feet below ground, runs the cool water through a heat exchanger to blow 55 degree F air, then returns the water to the aquifer. Conventional systems waste enormous amounts of energy cooling air that starts out as hot as 100 degrees F.

Next he designed in an 8,000-gallon tower to collect rainwater for bathing, dishwashing, laundry and other non- drinking use. Gray water is filtered separately and reused for irrigation. Organic waste – including food scraps that traditionally would go down a garbage disposal – is composted for the landscape and garden.

Courtesy of John Zona III

Zona chose to illuminate the home with LED accent lighting and low-voltage fluorescent lights – both of which produce light as warm as traditional incandescent lights. The home is wired to accept LED lighting throughout just as soon as the technology is affordable.

The cladding – surprisingly attractive vertical corrugated metal – reflects, rather than absorbs, sunlight.

“To have net zero home, you have to spend a lot of time thinking about every one of these decisions,” says Zona. “If you don’t site the home correctly in the first place, it’s an uphill battle all the way. ArchiCAD helped us orient the buildings and panels for both protection from the sun’s heat and maximum capture of the sun’s electrical potential. Every electrical device that goes into the home – pumps, fans, lights, and appliances – needs to be analyzed to ensure you don’t exceed 6.5 kwH. You need to consider: How much energy does this device consume? How long does it run? And how do you capture the benefits with techniques like efficient insulation? You need to end up with a surplus instead of a deficit.”

There are green concerns beyond sheer energy efficiency. In addition to the judicious reuse of water, all materials are locally sourced, and all wood scrap from building the home is being recycled into new boards.


ArchiCAD’s building information modeling (BIM) software – and its companion products from GRAPHISOFT, EcoDesigner for sustainable design and MEP Modeler for mechanical, electrical and plumbing design – enabled Zona to quickly model the house in three dimensions.

“I mean, how are you going draw the inside of a football with a 2D software and have any kind of accuracy?” Zona asks. “We probably never would have finished the design. The only way you can do it is with 3D BIM software like ArchiCAD. You can walk though the building and see how dramatic these spaces really are. You can understand the uniquely shaped spaces, including the thermal qualities of volumes two stories deep. You can experiment with different materials, colors, textures, and furniture placements inside and out. I’m treading new ground with these curved walls, and I wanted to see how they’d look and feel before I opened the bank account on construction.”

Courtesy of John Zona III

Once a building is modeled in ArchiCAD, the user can automatically pump out 2-D CAD-compatible 2D floor plans, elevations, sections and orthographic projections for the builders. “The drawings are automatic and five times faster than 2-D CAD, which is becoming a white elephant. ArchiCAD is hands down faster than 2-D CAD and easier. For this particular home, ArchiCAD was mandatory to make any sense out of what we were envisioning. As a result, our dream home has come true”.

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Cite: Graphisoft. "Using BIM to design a ‘Net Zero’ home" 08 Feb 2011. ArchDaily. Accessed . <> ISSN 0719-8884

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