Solar Photovoltaic (PV) System

The Schellers' home uses a 5.76 kilowatt (kW) solar PV system to harness the power of the sun. Two pole-mounted 2.88 kW arrays of solar PV panels tilt and move to collect as much sunlight as possible at every time of day.

The PV system is connected to the electric distribution system of Stoughton Utilities, allowing the Schellers to send electricity to the grid when their PV system produces power and purchase electricity from the utility when they need it. Bottom line: the homeowners can earn money by generating electricity right outside their front door!

For example, all electricity produced by the Schellers' PV system will be purchased at a special buy-back rate of 30 cents per kilowatt-hour (kWh), which is considerably higher than the retail cost of electricity. Let's say the estimated annual electricity production of the PV system is 10,000 kWh. If the Schellers are paid a special solar-buy rate of 30 cents per kWh, their annual payment for the generated electricity would be $3,000.

If the Schellers use an estimated 10,000 kWh of electricity per year, they will be billed at the approximate utility rate - 10 cents per kWh or $1,000 annually. This means their net "profit" from electricity sales to the utility over the course of a year would be about $2,000.

If these assumptions hold true, an average homeowner - with access to special incentives and federal tax credits - could significantly reduce the overall payback on the cost of installing a PV system to about 10 years.

Two Ground Source Heat Pumps (GSHP)

The GSHPs provide heating, cooling and hot water. Also known as a geothermal heat pump, a GSHP uses thermal energy from the ground to heat the home and provide hot water. In the summer, the system runs in reverse to provide air conditioning.

Structural Plumbing

Structural plumbing uses advanced plumbing designs and controls, eliminating the need to let taps run before hot water arrives at the faucet. This system reduces water waste and energy use while providing the occupants with a better performing hot water system.

Windows

Highly efficient, ENERGY STARŪ rated windows are strategically placed to take advantage of daylight and the best scenic views.

Air Sealing

Special attention was paid to air sealing during construction, with blower door tests to ensure the home met an aggressive air sealing standard.

Ventilation

Spot exhaust fans in the bathrooms and kitchen eliminate moisture and contaminants at the source. In addition, overall background ventilation is provided via an energy recovery ventilator, which reduces the amount of energy needed to condition the indoor air.

Simple Design

The Schellers' home is a New England Saltbox, a Colonial style of architecture. This two-story, pitched roof design its known for its strength and simplicity, which makes the building easy to insulate and air seal, minimizing energy loss through the 4,000 square-foot home's exterior.

Location

The Schellers' rural lot, located in the Town of Rutland and served by Stoughton Utilities, offers a number of energy-saving advantages. Southern exposure for most of the home's windows provides for optimal use of daylighting, and a wooded lot to the north protects the home from seasonal winds. In addition, the lot size is sufficient to accommodate the installation of the solar PV and GSHP systems. The Schellers' home is positioned near the road, and thereby prevented the disruption of more soil than necessary.

Insulation

Two-inch, R-10 insulation on the exterior of the basement walls and under the basement floor help prevent energy loss and improve the comfort of the home. The 2x4 basement walls are blown with BIBSŪ insulation. Above grade, R-5 insulation was used on the exterior, and BIBSŪ insulation was also blown into the 2x6 walls. In addition, close cell foam was blown into the box sill framing to provide air sealing and insulation in what is normally an energy efficiency weak spot for cold-climate homes.

Attention to detail

While the Schellers' GreenMax Home may be unique in its goal of net zero energy use, the construction methods used to build it are similar to most average homes today. Attention to basic details, such as insulation and air sealing, have helped make the home far more efficient.

Commitment

The homeowners will work with Stoughton Utilities and WPPI Energy to monitor their energy use and fine-tune the home's performance to ensure their energy use is truly net zero.