Editor's note: Last week we looked at a home that produces way more electricity than it uses. This week: a house under construction that may just break energy-saving records.

It's his latest and most challenging project in more than 30 years in the home building trade: a house that looks, on the outside, like any other new-build home still in the throes of construction.

But Michael Ginsburg, the builder, calls it not a home but a "thermal envelope."

After seeing for himself the efforts of homeowners and builders to produce solar electricity and hot water and energy-efficient buildings, Ginsburg felt he could do more.

So he set himself the task of building what he calls the S.E.E.D. - or, super energy efficient design home (his own acronym).

The "thermal envelope" moniker came about after he realized this: "That the wall is only a third of the shell of the thermal envelope. You've got the roof and you've got the floor."

Ginsburg, owner of La Mirada Homes, considered a number of construction materials - Insulated Concrete Form, straw bale, rammed earth - before settling on Structural Insulated Panels for the roof and outside walls (there are no bearing walls inside, so that the interior floor plan can easily be adjusted).

As for the floor, it's going to be fitted with radiant heating, and experimental radiant cooling.

The result - just months away, he hopes - will be a "near net zero home," one that looks likely to exceed regular residential standards set by the city of Tucson, and has already generated interest as a national prototype (see box).

Ginsburg says he is talking to investors about creating a subdivision of nine such homes - with a plan similar to this 1,935-square-foot one - on a 2-acre parcel.

An advantage for Ginsburg, he says, is that he's a custom builder who works for himself.

"I have the luxury of the time to research. I don't have committees to deal with, I don't have supervisors. For me the key difference is I started from scratch, not trying to take a current plan and make it energy-efficient."

The walls:

• Made of Structured Insulated Panels or SIPs, which take two pieces of board and sandwiches plastic foam insulation between them.

The floor:

• The entire concrete floor will have radiant heating, thanks to solar-heated hot water that moves through plastic tubes that are set on top of insulation boards. There will be no hot or cold spots, says Ginsburg. "It's a perfect thermal mass storage element that covers every square foot of the house."

• There is also radiant floor cooling, working the same way but circulating stored cold water. Ceiling fans then draw the cooled air through the return air ducts. There's an air conditioning unit for back-up.

• For an extra aesthetic punch, he is having his contractors grind down the concrete so that the stone and aggregate that make it up are exposed. This will then be polished.

The roof:

• Made of SIPs too, although the boards or panels are thicker.

The solar:

• Photovoltaic panels on the roof of the garage or carport, for ease of access should they need repair.

• Hot water is produced by solar panels and stored for use any time.

The windows:

• Milgard Windows' vinyl windows with dual pane low-e glass.

The orientation:

• The long side of the house faces south, and there are no major windows facing east or west - the hottest sides in the summer.

• An 8-foot deep front porch, and a 12-foot deep back porch, should shade the building from the daytime sun but still soak up evening sun.

• Shade trees and a trellis will also be used to block the sun.

The cost:

• It has cost Ginsburg $150 per square foot to build. He hopes to sell it for around $485,000.

The rest:

• When you build a house so extremely tight, says Ginsburg, you run the risk of "sick house syndrome." So he is installing a fresh air exchange system that pulls in outside air, independent of the air-conditioning unit.

• Energy Star-rated appliances.

• Gray-water recycling and rainwater collection.

How efficient is it?

Ginsburg has not applied to the U.S. Green Building Council, whose L.E.E.D. system rates and certifies buildings for energy efficiency. He says the process would have cost him too much money.

Instead he submitted his plans to the city of Tucson, which adopted the Residential Green Building Rating System in August 2009. A city spokesman said that the city told Ginsburg that when completed, the project is estimated to certify for an emerald rating.

Under the Building America program, a partnership between science consultants and the Department of Energy, California-based Davis Energy Group has been looking at Ginsburg's home as a possible prototype for an affordable net zero energy home - the program's ultimate objective.

The home is approaching 60 percent energy savings, and nearly 80 percent when the photovoltaic panels are included, says Davis Energy Group's David Springer. That's way above the 50 percent starting point they're allowing for all prototype homes.

Resources

• Contact La Mirada Homes at 529-2100.

• Davis Energy Group, 1-530-753-1100 or www.davisenergy.com