Many homeowners are under the impression that their windows are energy-efficient, though so many are not.  A window's energy efficiency is measured by more than just noticeable drafts entering your home.  There are a wide range of characteristics that can help you determine just how environmentally sound they really are.  The following checklist can help in determining if your house is protected against excess heat, cold, solar UV damage and other fundamental concerns.

Clear Labels and/or Manufacturer Efficiency Specs

Energy efficient windows are labeled to clearly indicate which consumer agency has evaluated them for environmental and efficiency criteria.

Energy Star Seal® Certified Label

Energy Star is the most well-known and trusted sources for product performance and energy efficient windows.  We've all seen that familiar star on their logo, and if yours' have it, you're likely in good shape depending on their age and condition.

National Fenestration Rating Council Label

NFRC-certification measures a window's U-factor, or ability to prevent heat from escaping during winter, while keeping it out in the summer.  NFRC labels are also used in the process of issuing the Energy Star® seal for a particular brand or line of windows.

Electrical Panel Energy Codes

You've likely seen these and not known what to make of them.  Window electrical energy labels will tell you the windows' U-factor, solar heat gain, visible transmittance and air leakage information.

Window Design & Features

How a window is made (materials, process, inspection, etc.) will play a huge role in how efficiently it uses energy and lowers your home heat & cooling expenses.

Window Frame Construction Materials

The materials that were used to make your windows can give you an idea of how energy efficient it is.  For example, windows made from vinyl or wood sources aren't as efficient as those made from steel or aluminum.

Single, Double or Triple Panes

You already know that two or three layers are better than one, and this is especially true when it comes to window efficiency.  If this is a key concern, consider upgrading to double or triple-glazed windows.

Condition of Weather Striping

Even the most subtle cracks or splits in your windows' weather stripping can prevent proper insulation.  Evaluate it closely to make sure that no tiny gaps or aging corners are allowing warm/cold air in our out.