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Engineering a small house that uses as much source energy as it produces on site during a year is intriguing to homeowners across the globe. The project objective is to create an affordable solar powered home that produces, on site, as much energy as it uses in a year. During the course of this project, five homes have been built and monitored to maximize affordable energy efficiency. These houses are located near Oak Ridge, Tennessee with 3500 HDD. This paper focuses on the fourth occupied house. It was built with well integrated envelope and equipment energy saving features. The envelope consist of eight inch thick insulated precast concrete foundation basement walls, 4.5 inch thick polyisocyanurate foam Structural Insulated Panel (SIP) walls upstairs; 8 inch polyisocyanurate SIP cathedral ceiling; and low U-factor and solar heat gain coefficient windows. The equipment consists of a heat pump water heater and a 17 SEER variable speed air-to air heat pump. The onsite renewable energy is generated by a 2.2 kWp roof mounted photovoltaic system. The precast insulated foundation panels were installed in 6 hours, the wall panels in 5 hours, roof panels set in 3 hours and the PV panels mounted on the roof in 2 hours. Thermal performance has been monitored with fifty sensors continuously for three years, gathering data every 15 minutes. Thermal couples monitor ambient, interior, air distribution, and hot water temperatures. Meters measure the flow of electricity to the air handler unit, water heater, compressor, inverter, refrigerator and incoming and outgoing electricity to the whole house. Water flow is also measured to collect hot water usage. Data provides detailed energy efficiency of various components of the house; the building envelope, water heater, space heat pump and whole house performance. The house performance is modeled and calibrated using the measured data. This model is used to extrapolate the performance in a Hot Humid Climate. The report concludes with some cost information. The house is served by an electric utility that offers solar credits which enable the average daily cost of all energy needs from off site for the first year of75 cents per day, and 41 cents per day for the second year. The benchmark house in this area is four dollars per day. The report concludes with how to get to zero energy cost a key steppingstone toward the ultimate goal of creating affordable zero energy.

Presented at Thermal Performance of Exterior Envelopes of Whole Buildings X – December 2007

Units: I-P