The building envelope includes the components of the building such as the foundation, roof, walls, doors, and windows that separate the interior and exterior environments of a home. An inadequately sealed building envelope has a significant and direct effect on the efficiency of any installed heating and cooling components.
Heat loss is responsible for the most significant energy drain on a home. Direct heat loss, or air leakage, accounts for between 25% and 40% of the total energy used for heating and/or cooling in a typical residence[i]. Air gaps around window and door frames, gaps or cracks in bricks, siding, stucco and foundations, as well as electrical and gas service entrances are the most common sources of air leakage.
Heat loss through temperature differential is also a major source of energy drain on a home[ii]. Temperature differential occurs when different components of the building envelope conduct heat out, such as attics, walls, basements, crawl spaces, pipes, and roofs.
There are a few of do-it-yourself projects such as using weather-stripping, caulking, or a non-expanding spray foam to seal around window frames and exterior doors. Sealing attic hatches and insulating recessed light fixtures are additional methods of decreasing air leakage.
In many cases, a home energy audit, performed by a qualified technician, is the most beneficial means of obtaining a thorough and accurate measurement of air leakage in the home. An energy assessment will also determine if further insulation is necessary to prevent temperature differentials in the home. It is important to remember that proper air sealing should be addressed first and it could possibly negate the need for further insulation.
When considering insulation, the term R-Value is frequently used, it indicates the material’s resistance to heat flow. Factors affecting the R-Value include material, thickness, and density. The higher the R-Value, the greater the insulating effectiveness of the material.
Because 50% to 70% of the total energy consumption of a home is used for heating and cooling, preventing heat loss will decrease utility bills and increase personal comfort in the home.
It’s the Little Things Too!
ENERGY STAR® qualified Compact Fluorescent Light bulbs, or CFLs, use 66% to 75% less energy than incandescent bulbs. Despite the slightly higher cost of these bulbs, they last 6 to 10 times longer than traditional light bulbs, which can equate to around $42 in energy cost savings over the lifetime of just one CFL[iii].
Turning off lights when leaving a room and unplugging small appliances when not in use, will help to reduce your energy costs.
Plug small electronics, such as cell phone chargers, iPod chargers, and computer chargers into a power strip or surge protector. When not in use, turn off the surge protector, as these charging devices continue to consume electricity even when they are not in use.
Lowering the thermostat to 65° if no one is at home during the workday or at night before going to bed, could save you up to 10% on annual heating costs[iv].
Taking advantage of ENERGY STAR® qualified appliances and electronics may further decrease your energy consumption and lower your utility expenses.
[i] U.S. Environmental Protection Agency. (2000).
Air sealing: Building envelope improvement (EPA 430-F-97-028).
[ii] Logan, K. (2010, November & December). The rise to retrofit.
Green source: The magazine of sustainable design, 107-113.
