Wednesday, July 12, 2006

Midwest Zero Energy Homes

Here is the executive summary of a report that just completed with some U.S. DOE funding (Award Number DE-FC45-05R530753). For a PDF of the full report email me at (wolter at

Several challenges facing the American economy encourage the construction of new homes able to meet their own energy needs using locally available renewable energy resources. These challenges include: high and highly variable fossil energy prices, global climate change, state and national energy trade deficits, reduced energy supply reliability, and increasing dependence on fossil energy imports.

A true Zero Energy Home (ZEH) is defined as a home able to offset any import of fossil energy by generating and exporting an equal amount of renewable energy over the course of a year. Homes that get close to this goal are considered zero energy homes.

Homes on the path toward zero energy:
1) Are sited, designed and built to use as little energy as possible while providing the comforts of home,
2) Use energy efficient appliances
3) Install high efficiency heating ventilation and air conditioning systems (HVAC),
4) Have occupants that are careful about how they use energy,
5) Produce onsite renewable energy (or purchase renewable power or credits),
6) Are designed and constructed so that in the future the home can meet all of its energy needs with onsite renewable energy.

ZEH homes and experts can be found employing ZEH technologies and designs across the Midwest. Links to Midwest ZEH case studies and experts are included in this report.

The greatest challenge is providing reliable space (and water) heating during the Midwest’s cold and cloudy winter months. A ZEH cannot rely solely on standard solar thermal systems or passive solar for winter space heating. Instead, it must rely on renewable energy that can be stored for weeks to months such as wood, thermal energy, or net-metered (banked) renewable kilowatt-hours (kWhs).

If ZEHs are to rely on renewable kWhs for heating, then the electrical heating systems must be very efficient. Ground source heat pumps (GSHP) are the most efficient space heating systems suited to the Midwest’s climate (they also provide very efficient cooling).

There are two general ZEH types, based on their method of space heating. The Urban ZEH that has a GSHP for space heating and cooling, a solar electric system for power generation, and a solar water heating system backed up by an electric hot water heater. The rural ZEH has a wood stove and solar thermal system for space heating and water heating and an onsite solar electric system or wind turbine for power generation.

The Urban ZEH would add about $55,000 to the price of a new energy efficient home while reducing its natural gas use by roughly 95% and electricity use by 75%. The price includes federal but not state incentives. The solar electric system is responsible for the majority of the added price.

Many new single-family homes built today are large. By reducing the size of new homes by 400 square feet, the home’s construction costs would reduce by about $36,000. These cost savings would cover much of the cost of making the home zero energy.

ZEH economics will improve if: fossil energy prices increase; energy system prices decline; utility’s encourage ZEH with incentives (through tariffs, buy back rates, financial incentives, financing, etc.); or States and/or the Federal government provide incentives for ZEH or ZEH technologies.

Key ZEH barrier reduction strategies include:
1. Target wealthy green innovator home buyers
2. Target successful Energy Star® home builders
3. Education through mainstream demonstration homes and detailed case studies
4. Ensure homes have curb appeal
5. Offer home builders market differentiation by offering new labels/logos such as “Green” Energy Star® home
6. Offer new ZEH services such as: guaranteed savings, maintenance agreements and system commissioning
7. Begin mainstream market transformation by promoting the “zero energy ready home”

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The view and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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