Transformations is now building most new homes to a new Zero-Energy Home platform. The energy usage is modeled with the REM/Rate software by an independent third party. The homes are inspected and receive a final as-built certification. These homes are designed to produce as much energy as they consume over a years time. That means, when a year goes by, the electric meter should be at or close to the same place as it was 12 months earlier. More energy is generated in the late spring, summer, and early fall, than is consumed in the home. The electrical energy is sold to the grid though what is called net metering. The electric company gives a credit for the excess energy produced by the home. In the late fall, winter, and early spring the home uses more energy to run the heating system and works off of the credit that was built up in the warmer months. Monthly base charges are still incurred. The energy usage of individual home owners will vary with different consumption patterns.

These homes incorporate solar electric panels (PV) on the roof. The system is usually 5.7 kW in size (or larger for the bigger homes), producing an order of magnitude of 6,800 kilowatt hours per year, depending on shading, solar orientations, and angle of the panels. We are currently using the Evergreen Spruce line of panels. A solar hot water heating system is installed on the roof. A SunDrum solar hot water system has been used that fits under the existing PV panels. It does not take up any roof space and increased the efficiency of the PV panels it is installed on. A test of the system showed a 7% bump in the electrical energy generated by the PV panels. A more conventional flat plate solar hot water collector is available as well if the roof space permits.

The homes are super insulated with 12 inch thick walls, in addition to triple pane glass, and 18 inches of insulation in the attic. Careful attention to air sealing is accomplished. The local Energy Star inspector was not able to measure the tightness with his “blower door” equipment on our first Zero-Energy home. He had to leave the job site, order another “ring” to install in the blower door testing apparatus, and return the next week to test again. We achieved a 175 cubic feet per minute rating at 50 Pascals pressure on that home.

Mitsubishi air source heat pumps are used to both heat and cool the homes. The peak heating load on our first Zero-Energy home was so low (10,500 BTUs), that you could heat the home with two 1500 watt hair dryers and an 80 watt light bulb! Each heating and cooling head has its own zone controls. To date, we have installed two, three and four zone systems.

The home comes with a heat recovery ventilation system. These units are designed to remove heat in the winter time and transfer it to incoming cool fresh air. About 64 percent of the sensible heat is transferred in the process. We are now exhausting the bathroom and select bedroom air through this heat recovery ventilation system and supplying fresh air to various locations in the house.

Please see the Solar Today and other articles in the News section at the right hand portion of the home page for more details.