Residential Energy Efficient Windows

Add value, beauty, and comfort to your home and money to your wallet!

No matter how old your home, it is important to have high quality windows to protect your family and your belongings from the elements of Mother Nature. While many start their window-shopping journey in search of something to add beauty and class to their home, many forget one of the most important reasons to replace your old windows with newer ones: energy efficiency! By stepping up to high efficiency windows, not only are you reducing the strain on the environment by cooling and heating your home more efficiently, you are saving money! On average, these new, energy efficient windows installed in your home will pay for themselves within three years through savings on your electric and gas bills. Your beautiful new windows are great for the environment and your pocketbook! In addition to what you save on your utility bills each month, your new windows could qualify you for energy tax credits and rewards from your electric company, making new windows more affordable than ever.

There are many window options available to the consumer, each offering energy saving properties as well as some other positive characteristics:

  • Double Pane – Double pane windows utilize two separate pieces of glass in a single frame with a layer of air between the panes. The still air between the two panes of glass is a good insulator. Double-pane windows insulate about twice as well as single-pane windows, so only half as much heat passes through the window. This idea can be taken a step further with triple pane windows.
  • Gas Filled – Gas filled windows use the premise of double pane windows, but the air between the panes is replaced with gases (either argon or krypton) that insulate better than air. Krypton is somewhat more effective in windows with less space between the panes, so it is often used in windows with multiple air spaces (such as triple-pane windows) to keep the thickness minimal, whereas windows with air or argon work best when the space is about ½”. Windows with krypton are usually more expensive, both because krypton itself is expensive and because the designs tend to be upper scale. Argon is nearly as effective and does not add much to the cost of a double-pane window if the application can support a wider gas gap.
  • Low Emittance (Low e) – Low e glass is fancy, scientific term for glass with a special coating on or in it, applied during the glass manufacturing process. This clear, microscopic metal oxide layer coating acts as an extra barrier to keep bad aspects of the sun out while allowing the good stuff to still shine in. More specifically, low e coatings allow short-wavelength sunlight (visible light) to pass through it but reflects long-wavelength infrared radiation and UV rays. UV light damages your skin, wood, fabrics, and causes colors to fade. The infrared light in sunlight is powerful. When it strikes an object it heats it up. These objects can be your tile floors, furniture, sidewalks, patio furniture, etc. As these objects cool off, they emit a low powered form of IR light. Low e glass reflects this form of energy. In the summer this helps to keep your house cooler, as the heat from objects outside is kept outside. In the winter, all objects in your home are heated (by either the sun or your furnace). This heat is also bounced back into your house by the low e glass.
  • Window Frames Materials– Window frames can be made from a variety of materials, including aluminum, vinyl, wood, fiberglass, composites (mix of multiple materials), and combinations (i.e. aluminum or vinyl clad with a thin layer of wood to look like a wood framed window). The frame can account for approximately 15% of the energy loss through a window, so it is an important consideration when deciding on what windows should go in your home. In general, wood, vinyl, and fiberglass frames are much better insulators than standard aluminum frames with no thermal break (a layer of urethane that interrupts the transfer of heat though the metal). Of these, fiberglass frames offer slightly better performance and durability. Keep in mind that various window manufacturers can add elements that minimize the frame’s thermal conductivity; for example, some vinyl frames are filled with foam insulation, making it more energy efficient than a vinyl frame with no insulation.
  • Spacers – In double- and triple-pane windows, the panes of glass are separated by spacers. The spacers are traditionally made of aluminum, even in wood, vinyl, or fiberglass frames, creating greater conductivity around the window edges. This makes the windows colder at the edges in winter, and water vapor may condense there as it hits the cold surface. New warm-edge spacers are made from better-insulating materials, and are recommended for cold climates. The biggest advantage to warm edge spacers is that they reduce condensation around the edge of the window.

The degree to which a window’s thermal conductivity is measured is called a U-factor. The higher the U-factor, the less energy efficient the window is. To give you a general idea of each window’s degree of efficiency, we have included a list of average U-factors for various window types as provided by ASHRAE (American Society of Heating, Refrigeration, and Air-Conditioning Engineers).

Whole Window U-factors of Sample Windows
  Aluminum frame w/o thermal break Aluminum frame with thermal break Wood or Vinyl Frame
Single Glass 1.30 1.07 n/a
Double Glass, 1/2″ air space 0.81 0.62 0.48
Double glass, low-e, 1/2″ air space 0.70 0.52 0.39
Double glass, low-e, 1/2″ air space 0.67 0.49 0.37
Double glass, low-e, 1/2″ space with argon 0.64 0.46 0.34
Triple glass, low-e, on two panes, 1/2″ paces with argon 0.53 0.36 0.23
Quadruple glass, low-e on two panes, 1/4″ spaces with krypton n/a n/a 0.22
Source: 1993 ASHRAE Handbook: Fundamentals, (Atlanta, GA:American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Incorporated, 1993).

Note: These are example of whole window U-factors of 3 ft x 5 ft windows. U-factors vary somewhat with window size. Ask the dealer for the specific values for the window you are looking at.


Many people think that their windows do not need to be replaced. However, significantly more homes need replacement than do not. The easiest way to tell if your home would benefit from new windows is to do some field studies. If you feel cold air coming in or your windows are cold to the touch (during winter of course), your windows are defeating your battle for energy efficiency. Just as they are letting heat out during the winter, they are letting heat in during the summer months, causing your home to be uncomfortable from temperature shifts and your air conditioning and heating units to work overtime.

If you home was built prior to 1980, chances are that it has wood framed windows. While wood is a good insulator, wood wears out fairly quickly, creating gaps perfect letting the outside in. Now, over 30 years later, if you have wooden window frames in your older home, they likely need to be replaced.

Since most homes lose about 25% of its heated/cooled air through its windows, it is advisable to highly consider replacing your windows if they are out-dated or inadequate. Take your time in deciding what types of windows you want, and which company you want to use. You will be repaid from your diligence with high quality, professionally installed windows that will add beauty, comfort and value to your home. Remember, there are a lot of window replacement companies out there, but only the best will have excellent references, insurance, warranties on their work as well as the windows themselves and a solid rating with the Better Business Bureau. Take your time and you will make the right decision, and you can soon enjoy lower energy costs and enhanced beauty in your home.

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