Building a 40% Energy Saving House in the Mixed-Humid Climate
- ORNL
This report describes a home that uses 40% less energy than the energy-efficient Building America standard - a giant step in the pursuit of affordable near-zero-energy housing through the evolution of five near-zero-energy research houses. This four-bedroom, two-bath, 1232-ft2 house has a Home Energy Rating System (HERS) index of 35 (a HERS rating of 0 is a zero-energy house, a conventional new house would have a HERS rating of 100), which qualifies it for federal energy efficiency and solar incentives. The house is leading to the planned construction of a similar home in Greensburg, Kansas, and 21 staff houses in the Walden Reserve, a 7000-unit "deep green" community in Cookville, Tennessee. Discussions are underway for construction of similar houses in Charleston, South Carolina, Seattle, Washington, Knoxville and Oak Ridge, Tennessee, and upstate New York. This house should lead to a 40% and 50% Gate-3, Mixed-Humid-Climate Joule for the DOE Building America Program. The house is constructed with structurally-insulated-panel walls and roof, raised metal-seam roof with infrared reflective coating, airtight envelope (1.65 air changes per hour at 50 Pascal), supply mechanical ventilation, ducts inside the conditioned space, extensive moisture control package, foundation geothermal space heating and cooling system, ZEHcor wall, solar water heater, and a 2.2 kWp grid-connected photovoltaic (PV) system. The detailed specifications for the envelope and the equipment used in ZEH5 compared to all the houses in this series are shown in Tables 1 and 2. Based on a validated computer simulation of ZEH5 with typical occupancy patterns and energy services for four occupants, energy for this all-electric house is predicted to cost only $0.66/day ($0.86/day counting the hookup charges). By contrast, the benchmark house would require $3.56/day, including hookup charges (these costs are based on a 2006 residential rates of $0.07/kWh and solar buyback at $0.15/kWh). The solar fraction for this home located in Lenoir City, Tennessee, is predicted to be as high as 41%(accounting for both solar PV and the solar water heater). This all-electric home is predicted to use 25 kWh/day based on the one year of measured data used to calibrate a whole-building simulation model. Based on two years of measured data, the roof-mounted 2.2 kWp PV system is predicted to generate 7.5 kWh/day. The 2005 cost to commercially construct ZEH5, including builder profit and overhead, is estimated at about $150,000. This cost - for ZEH5's panelized construction, premanufactured utility wall (ZEHcor), foundation geothermal system, and the addition of the walkout lower level, and considering the falling cost for PV - suggests that the construction cost per ft2 for a ZEH5 two-story will be even more cost-competitive. The 2005 construction cost estimate for a finished-out ZEH5 with 2632 ft2 is $222,000 or $85/ft2. The intention of this report is to help builders and homeowners make the decision to build zero-energy-ready homes. Detailed drawings, specifications, and lessons learned in the construction and analysis of data from about 100 sensors monitoring thermal performance for a one-year period are presented. This information should be specifically useful to those considering structural insulated panel walls and roof, foundation geothermal space heating and cooling, solar water heater and roof-mounted, photovoltaic, grid-tied systems.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Building Technologies Research and Integration Center (BTRIC)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE); Work for Others (WFO)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 1025816
- Report Number(s):
- ORNL/TM-2008/023; BT0101000; 400480000; CEBT114; TRN: US201122%%447
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
14 SOLAR ENERGY
BENCHMARKS
BUILDERS
CLIMATES
COMPUTERIZED SIMULATION
CONSTRUCTION
COOLING SYSTEMS
DUCTS
ENERGY EFFICIENCY
GEOTHERMAL SPACE HEATING
GEOTHERMAL SYSTEMS
MOISTURE
MONITORING
PROFITS
REFLECTIVE COATINGS
ROOFS
SELLBACK
SENSORS
SOLAR FRACTION
SOLAR WATER HEATERS
VENTILATION
HOUSES
Zero Energy Homes