Getting to net zero energy and a zero carbon footprint started by examining the energy usage in the house prior to the renovation. Recurve (formerly Sustainable Spaces) inspected all of the energy systems and modeled the existing home with energy analysis software. The results of the inspection showed that the house was losing large amounts of energy due to leaks in the floors, windows, walls, attic and ducts. Recurve also found the fireplace damper did not close, the shower vented air into the attic, and the kitchen exhaust fan penetration was always open. In addition, older appliances and a lighting system that used incandescent bulbs were wasting energy and money in operating costs.

Energy Efficiency

Improving the building envelope significantly reduced the heating and cooling needs. Recurve insulated and sealed the attic and sub-floor with open-cell foam insulation. The foam insulation has a R-value of 25, but achieves the insulating properties of R-60 because of  a proper installation by Recurve.

The exterior walls were insulated with dense-pack cellulose insulation which prevents any air infiltration. The cellulose is made from shredded newspapers and coated with borate as a fire retardant.  Recurve installed the cellulose and ensured it was properly placed by using infrared cameras.  Densely packing the insulation eliminates any air pockets and prevents the cellulose from shifting during seismic activity.

Following Recurve recommendations, new well-sealed and properly-sized duct work, a balloon fireplace damper, and custom-designed storm windows from Serious Materials were installed.

The old appliances in the kitchen and laundry were outdated and used huge amounts of energy. The dryer, stove, and hot water heater were powered by natural gas.

Moving to Energy Star-rated electric appliances lowered the energy costs and eliminated the use of fossil fuels. The 36″ new refrigerator requires half as much energy as the previous refrigerator and costs only $46 a year to operate. The new dishwasher use 41% less energy and much less water than the previous dishwasher. The new washing machine will save over $145 a year in energy costs.

The new stovetop is an induction range that uses a high-powered magnet to heat food, not an electric heating element.  Cookware must be made of magnetic material such as stainless steel (aluminum, ceramic and cooper pots are not).  When turned on, a magnetic field transfers energy to the pot.  The cookware heats while the cook top stays cool.  84% of the energy required is converted to heat to cook the food versus 52% for a standard electric burner and 40% with gas according to the U.S. Department of Energy.  The induction range saves energy and keeps the kitchen cooler.  Because the cooking surface is not hot, it’s safe around children and easy to clean.

Project Manager Lynn Kingsbury did a “lighting retrofit” was done at the house and all of the incandescent bulbs in the house were replaced with compact fluorescent light bulbs (CFL), light-emitting diodes (LED), and halogen bulbs. These use 75% less energy than standard lighting, generate 75% less heat, and last 10 times longer. Motion detectors turn off the lights when a room is empty. French doors installed in the family room let more natural light into the room.

Recurve monitors the energy usage at the house remotely to help the homeowner make decisions that reduce energy consumption and save resources.  Since the renovation was completed in May 2009, the home’s energy usage has dropped 62% from the year before.  That reduction occurred even with the installation of the hydronic air conditioning system by Recurve.  Prior to the renovation, the home did not have air conditioning.  During fall and winter, a programmable Energy Star thermostat is set at 65 degrees at night, 70 degrees in the morning, 68 during the day (when the house is usually empty), and 70 degrees at night.

Renewable Energy

The energy to heat and cool the house is generated on-site from rooftop photovoltaic panels installed by Sun Light and Power, and purchased renewable energy from the PaloAltoGreen program.  The reduction in energy usage allowed for a smaller solar installation at the house than what would  have been needed prior to the Recurve retrofit.  Photovoltaic (PV) panels generates energy on-site.  Sun Light and Power installed a 4.3-kW photovoltaic solar 20-panel system on the roof to convert solar energy to electricity to power the home.

The purchased renewable energy is provided by PaloAltoGreen, the city’s Department of Utilities’ 100% renewable energy rate program.  The utility generates renewable energy from local and regional, wind and solar energy resources. 97.5% of PAG’s energy supply is generated from wind resources in the Pacific Northwest and  2.5% is generated from four solar projects within the Palo Alto city limits.

The re-insulated building envelope, new lighting and electric appliances, and a home energy monitoring system reduce the energy requirements for the house.   Energy is supplied on-site with photovoltaic and solar thermal rooftop panels and off-site with purchased renewable energy from PaloAltoGreen.  These improvements accomplished the goal of net zero energy and no carbon emissions.