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. This estimate is based on energy modeling (using REM/Rate version 11.0) of cost-effective improvements made to 'typical' existing U.S. homes with a weighted composite of characteristics. The modeled results are corroborated by the field experience of professional building science contractors who have done air sealing and insulation work for more than 20 years.
The Residential Energy Consumption Survey (RECS) indicates that a large block of existing U.S. housing stock was constructed between 1975 and 1985, just after the 1973 oil embargo, when there was a new increased awareness of energy use in homes. As a result, EPA based its modeling around the common construction characteristics of homes built in this era as a proxy for a 'typical' existing U.S. home.
Construction characteristics for the 1975–85 era were determined based on a review of RECS data from the U.S. Department of Energy, 1997 EDS (Energy Data Sourcebook for the U.S. Residential Sector and earlier versions) data from Lawrence Berkeley National Laboratory, and other supporting data, including anecdotal experience of ENERGY STAR staff and stakeholders. Based on these sources, EPA assumed the following characteristics for a house from the 1975–85 era:
Geographic climate factors, regional construction styles (e.g., basement, crawl space or slab-on-grade), and fuel type characteristics (e.g., natural gas or electricity) were then proportionally weighted; and estimated energy use calculated for "typical" composite houses in two climates that represented a weighted average for a Northern and a Southern home.
For the purpose of energy estimating savings, EPA assumed that a knowledgeable homeowner or contractor could cost-effectively:
Note: In estimating savings opportunities, EPA considered that the 1975–85 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 1993–2000 MEC/NAECA-era equipment.
Based on these projected cost-effective improvements, EPA estimates the following potential energy and utility bill savings:
|Location||Site MMBTU¹ Savings||Utility Bill Savings (2007 data²)|
|Heating and cooling only||20%||19%|
|Heating and cooling only||23%||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.