Beginning with their existing small, energy-efficient duplex home, Mary Kraus and her family set out to achieve the goal of zero net energy. The process began with careful modeling and measuring to determine the best strategies for efficiency, which included:
• targeted air sealing
• reducing plug loads by updating appliances
• new air-source heat pumps replacing an existing propane boiler
• upgrading ventilation system from exhaust-only to heat recovery ventilator
• super-insulated electric hot water tank providing backup for the solar hot water system
• 5.9 kW PV array covering energy uses
The results reduced energy usage by 23%, turning the house into a net energy producer and improving the overall comfort, with a payback period of only 9 years.