A zero energy home in Oklahoma
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...
This house has been built by Ideal Homes, based in Norman, Oklahoma, and is located in its Valencia community in Edmond, also in Oklahoma.
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
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