Energy Efficiency



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Solar PowerBuilding Envelope

Improvements to a building envelope (a building's shell) are one of the first places you should focus on when upgrading your existing facility. Start with the low cost/no cost opportunities. Like the lighting system, these factors are key to properly sizing the heating and cooling system during new construction or major upgrades.

These elements of the building are a major investment that should be purchased on a "life-cycle costing" or return-on-investment basis, rather than lowest initial cost. Over the life of the building, the operating savings in energy alone will far outweigh the initial cost of these items. Plus, in the case of new construction, it will be less costly to "do it right the first time," than to make even more costly upgrades to insulation, windows, walls or roofing material later.

The sections below will help you learn how to make your facility more energy efficient through improvements to your building shell. For additional information that may be applicable to your small commercial facility please visit ENERGY STAR Home Sealing.


Insulation is a critical component of every facility, helping to keep you cool in the summer and warm in the winter. Always insulate your new facility to model building codes, which are discussed in the New Building Design section of this ENERGY STAR Guide. For retrofits, use these codes as guidelines to ensure that you get the amount of insulation that will save you energy and be cost effective.


Energy-savings opportunities can be achieved by carefully choosing roofing materials and by purchasing ENERGY STAR qualified roof products when possible. Some areas that should be considered when upgrading your roof include:

  • Insulation: When specifying or replacing a roof, insulation can be placed under the roof.
  • Radiant Barriers: In addition to traditional insulation, radiant barriers save energy both in the summer and winter by re-directing radiant energy in the facility.
  • Cool Roofing: These systems lower heat gain for facilities by reflecting the sun's radiant energy, saving energy on air-conditioning. Consult your roofing and HVAC professionals to learn if cool roofing is an option for your facility.

To learn more about energy-efficiency opportunities for roofing visit:


Exterior walls (and those connected to unconditioned spaces) should be insulated. When exterior walls are being constructed or are bare during a renovation, consider a quality building wrap. These materials have a low cost per square foot of material and can help drastically reduce air and moisture infiltration into the conditioned space.

To learn more about building wraps visit DOE EERE's Consumer's Guide: Combination Air Barriers/Vapor Diffusion Retarders.


A single-paned window has an R-value (measure of the ability to prevent heat flow) of 1, making it little more than a hole in the wall. Fortunately, in recent years, double-paned windows, along with other energy-efficient features, have become more standard. Older facilities can likely benefit from improvements to windows. Improvements you should consider when upgrading your windows and frames include:

  • Purchase ENERGY STAR qualified windows, which feature a combination of new technologies that save you energy and money
  • Double or triple-paned glass
  • Inert gas (e.g., krypton, argon, or nitrogen) fill
  • Low-emissivity, advertised as Low-E, glass/film or other advanced coatings/films
  • Window tinting appropriate for your region and facility orientation
  • Insulated frames, low-conductivity materials

Many vendors are now promoting the advantages of window films - ranging from simple tints that block incoming light, to films that provide performance similar to Low-E glass, and advanced coatings that block specific wavelengths of light.

To learn more about windows visit:

Slabs and Foundations

Slabs and foundations are frequently overlooked areas where energy savings can be realized. Just like walls and roofs, there are insulation opportunities for these areas that will save you money. For new facilities, you should consider a vapor retarder between the foundation and the slab or earth. Vapor retarders reduce the amount of moisture, and other potentially harmful vapors, that can pass through slabs and foundations and add to discomfort and indoor air-quality issues in your facility.

Learn more about vapor barriers visit DOE EERE's Consumer's Guide: Combination Air Barriers/Vapor Diffusion Retarders.

Tightening An Existing Building

There are many low-cost/do-it-yourself actions you can take to help your facility reduce air leakage and costs. These actions include:

  • Filling gaps around doors and window frames with caulk, spray foam, and insulative batting.
  • Checking window and door weather stripping. If weather stripping is missing, hard, or cracked replace it.
  • For exterior doors with a gap underneath, (e.g., if you can see daylight) install door sweeps.

For more information on building envelopes, visit these links:


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