There are many factors to energy efficient windows.

Benefits of Natural Light

And let’s face it, windows are not a small purchase. We want you to be prepared when you buy new windows, so we’ve done some work for you. This way you’ll be better educated on your window purchase and know what to look for when you shop for energy efficient windows.

Here are a few key things to look for when shopping for energy efficient windows.

1. Glass

Glass packages have the greatest effect on your window energy efficiency. You may pay a little more for a great glass package up front, but you’ll save more in the long run. Here are some glass package options to keep in mind.

Low E – Reflects infrared light keeping heat inside in the winter and outside in the summer. It can also help keep your carpets and furniture from fading.

Gas Fill – Either Argon or Krypton can be placed in between glass panes to provide greater insulation than regular air.

2. Material

Not all window materials are created equal. Windows come in a number of different materials, including vinyl, wood, aluminum, fiberglass and composite.

Energy Efficient Windows

Here is a breakdown of the different materials.

Vinyl windows are the most affordable. They’re also long lasting, energy efficient and can be customized to fit any size opening. And unlike wood, they will never need repainting.

Wood windows are slowly being replaced by vinyl windows. And for good reason. Although they are energy efficient, wood windows are high maintenance. They have to be painted or stained regularly to remain protected from the elements.

Aluminum windows are low-cost and low-maintenance, but offer the least energy efficiency of any window material.

Fiberglass windows offer the strongest window frame, but they’re certainly going to cost you. You may pay a healthy 15-30% more for fiberglass windows than you would for vinyl.

Composite windows combine multiple window materials to take advantage of the benefits of each. Although these windows typically perform well, they are the most expensive window in the market.

In summary, out of all these window material choices, most homeowners choose vinyl because they’re durable, affordable and energy efficient.


ENERGY STAR is a government supported program that uses a specific criteria to define an energy efficient window.


How does ENERGY STAR determine what makes energy efficient windows? By measuring four different parts of the window: the glass, the gas, the spacer and the reinforcement. The combination of these factors influences the unit’s U-value and solar heat gain, both of which are drivers for meeting ENERGY STAR performance level.


To be labeled as an ENERGY STAR product, the U-factor and SHGC (Solar Heat Gain Coefficient) ratings must be less than or equal to those established by ENERGY STAR.

  • U-value The U-value or U-factor is commonly described as the amount of heat transferred through a material. The lower the U-factor, the slower the rate of heat flow and the better the insulating value.
  • Solar Heat Gain Coefficient (SHGC)  The SHGC refers to the amount of heat from the sun that windows and doors allow into the home. The lower the number, the greater the ability to reduce the amount of heat absorbed into the home.

Want to learn more about energy efficient windows? Read 4 Benefits to Buying ENERGY STAR Windows.