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The devil is in the detail when developing a zero energy house as it is with so many things. This space is used to point out some of them.

RADIANT BARRIER

It's the mate to attic insulation. Radiant barriers help keep heat out of the house in the summer and heat in in the winter. Often little more than aluminum foil for houses, but LP TechShield comes in board form and was used by the builders of the fourth home (i.e. near zero) down on the right.

Seeking Zero Energy Homes

Examples of homes that have eliminated utilities bills or have come close. Current count: 7.

Zero energy homes resemble mythological creatures. They are so rare that few people have ever seen one and sometimes when they do or think they have seen one it turns out that the house isn't a zero energy home after all.

They may have been built with the intention of becoming one. They may have many energy savings features and solar panels on the roof, but at the end of the month the utilities bill still arrives.

This however, is not such a bad thing for anyone interested in developing a zero energy home. It gives you a chance to see what it takes to get to zero by seeing how some homes made it while others fell a little short.

The idea on this page is to line them up, hits and near misses. They should come with enough credible information available on them to see how the energy is used in the home. They'll also need to be affordable homes, that is, a house you could find on Main Street and they must be connected to the utilities grid. They are in no particular order and we'll add to the list as we go along.

What we see right away are a few common themes. The homes are much better insulated than most houses. Air conditioning and heating are much more efficient and Energy Star appliances are standard.

The latest one is the first production townhome and it's in a Pittsburgh development called Riverside Mews. It's not cheap at $489,000, but is classic zero energy. In fact, the 1,850 square foot house has a -4 HERS rating. A good part of the credit goes to a ceiling insulated to R-60 and walls to R-40, with the ground floor at R-20. It's heated and cooled by a geothermal heat pump with a 450-foot deep vertical ground source loop. The pump comes with a desuperheater – an attachment that provides for hot water – too. The house has LED lighting and there’s 8 kilowatts of solar panel on the roof.

The next one is near Albuquerque in Rio Rancho, New Mexico and is as good a choice as any to lead the way. It has a Home Energy Rating System (HERS) rating of 0 and is has a platinum Leadership in Energy and Environmental Design (LEED) ranking. It's got good size at 1,665 square feet and a decent price at $258,000. It was built by Artistic Home last year and was built with the idea of being the first of many zero energy homes in the Rio Rancho development.

Among the features that helped secure its zero rating are R-21 insulation in the walls and R-50 in the ceiling. It also has solar electric panels (4.5 kW) and solar thermal panels on the roof.

The next one is in Townsend, Massachusetts and also has a fine pedigree. Its builder - Scott Carter, who heads up Transformations, a small development company in the eastern end of the state - claims it has a Home energy Rating System (HERS) rating of 0. Better still it is a production home for sales at a truly affordable $195,000 and its credible too. The house is one of the six entries in the Massachusetts Challenge, which is a competition to build zero energy homes. The winners will be picked in December.

A price this low for a zero energy home just doesn't happen anywhere this side of subsized housing, but all those good efficiencies are there. It has solar power, triple pane glass and lots of foam insulation. The house also has some nice extra touches like a SunDrum solar water heating system that captures the heat build-up behind the house's 5.7 kW solar panels on the roof and pumps into the hot water heating system.

Size is no small factor in the reason why the house reached zero. It is only 1,232 square feet, but it also has three bedrooms and as you can see looks no different than many homes in its price range. Indeed, the house could have looked a little less like the neighbors by loading more windows on the south side (i.e. right of picture) and less on the west for a better passive design. That way, it might gotten away with less PV so the house could sell for even less.

The next house was built in Tucson as a partnership between the NAHB Research Center and the John Wesley Miller Companies. You're not going to mail the plans for this house up to Grover's Corner, but you've got an all-electric house that is right at home where it belongs in the Southwest and can be example for buyers and builders in that area.

The home falls just short of zero energy. It used a net 1,578 kwh in 2005, when figures were last documented. At a U.S. average $.10/kw that's a bill of $157.80 for the year or less than 10% of the U.S. average.

The builders may have been able to do any of a number of things to make it all the way to zero - and beyond. Insulation is below the DOE recommended level. Instead of the DOE's R-18 walls and R-49 ceilings, the Tucson home has R-13 and R-41, respectively. Additionally, the ceiling insulation is made up of fiberglass batts instead of the more effective polyiso. Following those recommendations alone might have enabled the house to make it to zero.

If more efficiencies were need, the builders could have gotten windows with lower U-factors than the U-.32's they installed. Another way to cut energy use would have been, as noted in heating and cooling, to have a central air with a higher EER. The house has 18, but it could have 20 or higher.

These are all tweaks, but that's all the house needed because the home is literally a powerhouse. It has a 4 kW solar array on the roof and being in the sunniest place in the country it gets an incredible 7,000 kw out of the array so it doesn't get much electricity from the local utility or as much energy reductions as homes elsewhere may need.

One of the older zero energy houses sits in Lakeland, Florida It's over decade old and was built by the Florida Solar Energy Center and builder Rick Strawbridge.

It's a rare attempt at building a zero energy home in that it can be judged to see if it's measuring up because Strawbridge built one of his standard homes on the next block over. The two are the same size and are oriented in the same direction, only the one meant to reach zero energy has two sets of solar panels on a light-colored roof instead of a simply dark roof.

When you compare the energy of the two you find some big differences. The standard home used 22,600 kwh in one year, while the home with solar panels used 70% less or 6,900 kwh. It has a 4 kw-solar array like Tucson, but producing just 5,100 kwh. (Florida, the Sunshine State, is nevertheless not as sunny as Arizona). Subtracting production from consumption and you find that the Lakeland solar-equiped house drew 1,800 kwh from its utility company. That meant the house was 8% short of zero energy in its first year.

Any energy use could probably be eliminated in the same way they may have been in Arizona. Instead of R-10 wall and R-30 ceiling insulation, the house could have met the DOE recommendations and the builder could have been a central air with higher than 15 EER system that's in the house.

Outside of Philadelphia in Perkiomenville, Pennsylvania are two near-zero energy built by developer Jackie O'Neil. Both earned a Gold ranking for Leadership in Energy and Environmental Design (LEED) from the U.S. Green Building Council in 2005, the first in the nation to make the grade. Less than 500 homes in the U.S. have garnered a gold or platinum, the one higher ranking. Energy conservation is only one factor in the rankings and a house doesn't need to be a zero energy home to win a ranking, but it helps.

The homes have two of the killer applications for reducing energy consumption: structurally insulated panels (SIP) and geothermal heat pumps. The houses are also loaded up on the production side with 5.25 PV systems. This being the northeast however, the electricity generated was only good by regional standards. For example, O'Neil lives in one of the houses and she squeezed just 2,911 kwh out of her solar array during a full year. Fortunately, given the strength of her energy reductions, the house only used 2,845 kwh of electricity during that period for a net excess of 2%. However, she does use natural gas for cooking and has a fireplace.

The first zero energy home (2002) built as part of the Department of Energy's Building America program can be found in Livermore California.

The home stands out from most zero energy efforts because of its size. It is the rare one larger than the average American home (i.e. 2,500 square feet) with just over 3,000 square feet of space. Note: the solar panels laying flat on the A-frame roof, the more common position than the mounted panels on the Tucson roof.

The home produced more electricity than it needed, but reduced natural gas needs only by 45%. Ways it could have done better? On several fronts. A more efficient furnace than the 94 AFUE one now in the house, higher rated polyiso insulation than the R-38 cellulose the home has in the attic and, of course, if the house was smaller it would need less natural gas to heat it.