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A "typical" zero net energy home is designed to exceed minimum code standards.
Zero net energy simply means that a home uses no more energy from the electrical grid over a given period than it produces on site. It will often incorporate advanced design and construction techniques and may include some (or all) of the following elements:
- Advanced insulation materials such as SIPs, ICFs, and/or advanced, high R-value insulation packages.
- Efficient use of building materials to minimize waste and reduce cost, i.e. advanced framing.
- Balanced mechanical ventilation systems, including well-designed exhaust-only fan systems, Energy Recovery Ventilators (ERVs) and Heat Recovery Ventilators (HRVs).
- Super high efficiency HVAC systems including inverter driven or geothermal heat pump technology.
- High efficiency water heating including on-demand, indirect, and solar hot water systems.
- Properly sized HVAC systems, including carefully designed ducts, which minimize leakage.
- Air sealing and tight construction (i.e., less than 0.3 cfm50/square foot).
- Optimal solar orientation with advanced glazing based on orientation.
- Solar thermal water and/or photovoltaic (PV) systems, wind, and additional on-site generation.
- Low Load Home Construction: Low heat loss on the order of 10 MBtu per square foot of conditioned space.
Frequently Asked Questions
Below are some commonly asked questions about zero energy home construction and the CT Zero Energy Challenge:
What does "zero net energy" mean?
- Zero net energy simply means that a given home uses no more energy than it produces on site. For example, if a home used 7,500 kilowatt-hours of electricity over the course of a year but it produced 7,500 kilowatt-hours of electricity from a solar PV array over the same period, it could be considered a zero net energy home.
What does mechanical ventilation mean?
- Mechanical ventilation is a way of controlling the amount of air that enters and leaves a building. In a very well constructed, well insulated and air-sealed home, measures must be taken to ensure that the home is still able to "breathe" to prevent mold and rot and to ensure healthy air circulation. This can be achieved through various means, including something as simple as a continuously running exhaust fan in a bathroom, or as complex as a heat recovery ventilator (HRV) that exchanges stale indoor air with fresh outdoor air while maintaining the same indoor air temperature.
Must a home include on-site power generation to reach zero net energy?
- While homes are being built today that require very little energy use (such as Passive Houses), it is virtually impossible to achieve zero net energy without some kind of on-site energy production. This can come from various sources, including solar PV, solar thermal, or wind, depending on the specific site conditions.
How do I select which HERS rater to use?
- There are various ways to find a HERS rater in your area. If you live in Connecticut, CL&P and UI have a list of HERS raters on their web sites. You can also check out the national Residential Energy Services Network site which has a list of HERS raters from across the country.
What programs are available to help build a Zero Energy home?
- A number of state and federal programs exist to help you learn about and finance the construction of a near zero energy home. The Residential New Construction program (in which all the Challenge participants are enrolled) provides monetary incentives for various aspects of high efficiency building, including ENERGY STAR certification, insulation, and geothermal systems. On the renewables side, the CT Green Bank offers rebates for the purchase of solar PV.