Estimating Energy Savings from Improvements Made to the 'Typical' Home
For the purpose of energy estimating savings, EPA assumed that a knowledgeable homeowner or contractor could cost-effectively:
- Seal air leaks throughout the house, focusing on leaks to the attic space, through the foundation, and around windows and doors. An average documented baseline value of 0.94 ACHNAT (natural air changes per hour) was used for Southern homes. Southern homes were estimated to be improved to a leakage level of 0.50 ACHNAT.
- Add insulation to improve R-values from the average documented attic insulation values of R-13 in the South to R-38; and improve floors over crawl spaces from R-0 to R-11.
Note: In estimating savings opportunities, EPA considered that the 197585 construction era coincided with the period after the 1973 oil-embargo when early residential energy conservation measures were first becoming widespread (e.g., storm windows over single-pane/clear glass windows, some caulking & sealing to reduce air leaks, increased attic insulation, etc.). EPA also assumed that original, as-built HVAC and water heating equipment was replaced in the 1990s by 19932000 MEC/NAECA-era equipment.
Based on these projected cost-effective improvements, EPA estimates the following potential energy and utility bill savings:
Site MMBTU¹ Savings: 13%
Utility Bill Savings (2007 data²): 11%
Heating and Cooling Only
Site MMBTU¹ Savings: 23%
Utility Bill Savings (2007 data²): 20%
¹ Million British Thermal Units of energy
² From US Dept. of Energy, Energy Information Administration 2007 Short Term Outlook projected US natural gas and electricity prices.
Conservatively rounding these projected energy and cost savings, and corroborating modeled results with the field experience of professional home energy contractors, EPA estimates that homeowners can typically save up to 20% of heating and cooling costs (or up to 10% of total energy costs) by air sealing their homes and adding insulation in attics, floors over crawl spaces, and accessible basement rim joists.