be a Net Zero Energy Home? Should Your Next Home By Beth Shady I
f you are in the planning stages of building a new home or doing a significant remodel to an existing one, you are most likely considering some form of an energy
efficient method to heat, cool and power your home. Net zero energy is the simple concept that a home generates the same amount of energy that it consumes on an annual basis. This is accomplished when the right combination of very efficient mechanical, lighting, building materials and appliances are matched with properly sized solar systems to achieve an annual net zero energy balance. David Knight of Monterey Energy Group, a mechanical engineering and energy efficiency-consulting firm located in Pacific Grove, California, started Net Zero Energy Certified (NZEC) in 2009. I sat down and talked with David to learn more about the mechanics, costs and bene- fits of net zero energy. BS: One of the common concerns we hear with
regard to solar power and green building is that it is too expensive and that the payback takes so long that it hardly seems worth it. Is building net zero energy
affordable for the average homeowner? DK: If you had asked me that question two years ago I
would have said that concern was absolutely true. Today, however, recent significant reductions in the cost of grid- tied solar electric systems (approximately 50% last year) combined with a 30% uncapped federal tax credit have made these systems very affordable compared to the grid. In addition, solar electric panels are putting out more
energy per square foot, which makes them easier to inte- grate into the building. Another factor is that the overall efficiency of homes keeps improving. Better insulation, energy efficient lights, windows and HVAC equipment, all standard in today’s new homes, when combined reduce the demand for energy. BS: What mechanical equipment innovations do you
see that make all electric DHW and space heating with solar power more viable?
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Recent significant reductions in the cost of grid-tied solar electric systems have made them much more affordable for the average homeowner.
DK: The introduction of the air-to-water heat pump to
the U.S. market has been a boon to the net zero energy concept for hydronic heating contractors. These electric devices, for example the Daikin Altherma, use variable speed inverter technology to efficiently produce hot water for domestic and space heating. These units are reversible and can also be used for cooling, which opens up a huge untapped market for hydronic contractors, who can now use chilled water for air conditioning. In colder climates, there is a 30% federal tax credit for geo-exchange heat pumps. These systems not only con- vert electricity into hot or cold water but their capacity and efficiency remain constant, regardless of the outside tem- perature, due to the constant temperature surrounding the earth.
BS: How does a grid-tied solar electric system work? DK: These are simple, very low maintenance systems
that convert sunlight into electricity. When the sun is out and your home energy consumption is typically low, the excess energy generated literally spins your electric meter backwards; you are essentially selling electricity back to the grid. Think of it like rollover minutes on your cell
Continued on page 71 January 2011
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