According to Professional Builder, the first zero energy home costing less than $200,000 has been built in Oklahoma. This house produces as much energy as it consumes in a year and combines "renewable energy technologies with advanced energy-efficient construction." This environmentally friendly house is just a prototype and not available for sale. But as it has created lots of interest, I would not be surprised if its builder decided to add it to its catalog. Read more...
But what exactly is a zero energy home (ZEH)?
A ZEH is connected to the utility grid, but at off-peak time periods, it generates more power than it uses by combining renewable energy technologies with advanced energy-efficient construction. As a result, a ZEH lowers the power demand on its utility provider. It produces about as much energy as it consumes during a year, so it is considered to achieve "net zero" energy consumption.
Of course, you think that such a house costs much more than an ordinary one? Not exactly.
"What [Vernon McKown, co-founder of Ideal Homes] did," says George S. James, Building America project leader for Ideal Homes' affordable ZEH, "with my Building Science Consortium, is build a prototype to see what it would take to really do it at a price, at least in Oklahoma, that was not excessive. His houses normally sell for about $125,000, something like that. With the 5.3 kW photo cells and the ground source heat pump and so on, the selling cost is about $200,000."
So let's look at some more details about this test house.
Ideal Homes normally incorporates energy-efficient construction methods like fresh-air indoor HVAC systems; low-e vinyl windows; and insulation systems in walls, ceilings and around foundations. In addition, for the ZEH, it placed photovoltaics on the south-facing roof to capture energy from the sun and help offset consumption.
Below is a schematic diagram of a solar energy system such as the one used by Ideal Homes (Credit: Building Science Corporation).
[It also] used ground source heat pumps buried underground to harness the earth's constant temperature to heat in winter and cool in summer; installed tankless hot water systems that heat water instantly when the tap is turned on, conserving energy by not maintaining heated water 24 hours a day; and added energy recovery ventilation to maximize operating efficiency.
And below is an illustration showing how a tankless electric water works (Credit: Building Science Corporation).
And here is the legend in case you find difficult to read it: 1. A hot water tap is turned on; 2. Water enters the heater; 3. The water flow sensor detects the water flow; 4. The computer automatically ignites the burner; 5. Water circulates through the heat exchanger [coil]; 6. The heat exchanger heats the water to the designated temperature. [This takes only 5 seconds]; 7. The heater can provide you with endless hot water continuously.; 8. When the hot water tap is turned off, the unit shuts down automatically.
As mentioned above, this ZEH model is a prototype. It will be rented for one year before being sold. But I'm pretty sure that such a model will find a spot in the catalog of Ideal Homes.
For more information about this specific home, here is a direct link to its characteristics. As this URL is so long that it might change, please use a search engine if this page becomes unavailable.
And if you're interested by energy efficient homes, here is a link to a long presentation by Betsy Pettit, from Building Science Corporation, Affordable Housing: Toward Zero Energy (PDF format, 70 pages, 4.93 MB), from which the above pictures have been extracted.
Sources: Felicia Oliver, Professional Builder, May 1, 2006; and various web sites
You'll find related stories by following the links below.