Storm Windows

What should you consider when purchasing storm windows?

Before purchasing storm windows, consider these questions:

• What is a “low-e” storm window? A storm window with low-e glass has a microscopically thin, almost invisible, durable coating that reduces heat loss through the window glass when it is cold outside, saving on heating bills. Some low-e glass also has a low solar transmittance (Tsol) rating that blocks heat coming in from the outside and can help to keep your house cooler in the summer, saving on air conditioning bills. Some types of durable plastic storm windows may also have low-e characteristics.
   
• Why are ENERGY STAR certified storm windows better than other storm windows? The ENERGY STAR label makes it easy to select low-e storm windows that are designed to deliver cost-effective energy savings in your area. ENERGY STAR certified storm windows are tested and certified to meet the program requirements and are subject to additional routine performance verification testing.
   

• Which ENERGY STAR certified storm windows are best for my location? The climate where you live affects which low-e storm window product is best in your location. Therefore, every ENERGY STAR certified storm window has a label with a map to indicate which part of the country that product is designed for. Look for the label to determine whether the storm windows you are considering are ENERGY STAR certified in your location.
  
   

  
  North/North-Central Zone Label
  
  North-Central/South-Central/Southern Zone Label
  
   
• How much energy can I save with ENERGY STAR certified storm windows? Your energy savings can vary greatly, depending on where you live, the size and efficiency of your home, and the performance of your existing window system. You can find energy savings estimates for typical homes on the ENERGY STAR storm windows overview web page.
• How do ENERGY STAR certified storm windows differ from ENERGY STAR certified windows? Storm windows are installed as attachments to existing primary windows. Exterior storm windows are installed on the outside of your primary windows, and interior storm windows are installed on the inside of your primary windows. On the other hand, ENERGY STAR certified primary windows have a full frame and at least two layers of glass, which may also have low-e coatings. Consumers completely replace their existing primary windows when installing ENERGY STAR certified primary windows. See the web page for ENERGY STAR certified windows, doors and skylights for more information about the benefits of full window replacement.

What else should I consider in my purchasing decision?

• Are your current windows still in good condition? Storm windows work best when installed over working primary windows that are in good condition. If your current windows are rotted, not operating properly, or damaged beyond reasonable repair, adding low-e storm windows may not be appropriate. Instead, consider replacing them with new ENERGY STAR certified windows.
   
• Are your current windows single-pane or double-pane with clear (not low-e) glass? Low-e storm windows offer the most savings potential when installed over single-pane windows that do not have low-e glass. You will also save energy with low-e storm windows installed over double-pane windows that have clear glass, but you should expect a longer payback period.
   
• Do your current windows have metal frames? It is very important to use thermal breaks (small non-metal separators) when installing ENERGY STAR certified storm windows over metal-framed primary windows. Storm windows typically have aluminum frames, and this can conduct outside heat or cold through the metal frame of the storm window, diminishing the expected comfort and energy savings.
   
• Is your home historic? Low-e storm windows can be a good option if you live in a neighborhood with historic preservation requirements or you like the historic look of your original windows. Check to make sure that the historic preservation requirements in your neighborhood (if any) allow the use of storm windows.
   
• Are your current windows tinted? If your current windows already have tinted glass, adding a low-e storm window may reduce the visible light transmitted through the window, making them even darker. Some people prefer tinted glass to reduce glare, while others prefers more daylight.
   
• Do your current windows open and close? Interior and exterior storm windows are available in both operable and fixed models. Choose a storm window that matches the operability of your current windows. This is especially important when installing storm windows in bedrooms and other places where emergency escape and rescue windows may be needed or are required by building codes.
   
• Are your current windows difficult to clean? Adding storm windows to older, difficult-to-open windows may make cleaning windows more difficult.  Consider storm windows with features designed to make cleaning easy.
   
• Is your neighborhood or street noisy? Adding storm windows can be an inexpensive way to reduce noise from outside, making your home somewhat quieter.
   
• Do I need my storm windows to have safety glass? Safety glass is stronger than regular glass and is designed to shatter into little pieces (instead of larger, more dangerous shards) when broken. There may be state or local residential building codes that require safety glass in storm-prone regions or more accident-prone locations in the home (near stairs, for example). Check your local building code requirements for more information.
   
• Do you live in a place where the temperature gets extremely hot (above 115 degrees Fahrenheit)? In very hot climates and under certain conditions, low-e storm windows can trap heat between the original window and the storm window. If you already have double-pane or low-e coated windows and you live in a hot, sunny climate where the temperature frequently goes above 115 degrees Fahrenheit, you should consider awnings, solar screens or full replacement with ENERGY STAR certified low-SHGC windows as an alternative to storm windows.
   
• Should you have a professional install your ENERGY STAR certified storm windows? If your ENERGY STAR storm windows are not installed correctly, you may not realize all of the possible energy savings benefits. Professional installers can correctly install storm windows and inform you of local building code requirements and other considerations. All ENERGY STAR storm windows are required to include (or have a web link to) detailed installation instructions

Be sure to look for the ENERGY STAR when shopping for storm windows

Current Specification Effective Date:  September 5, 2018

ENERGY STAR certified storm windows must meet the emissivity, solar transmittance (Tsol), and air leakage requirements based on climate zone.

Scope:

1. Included Products: Products that meet the definition of exterior and interior storm windows that are intended for use in residential buildings as specified herein and are eligible for ENERGY STAR certification, with the exception of products listed under excluded products.
    
2. Excluded Products: Products described below are ineligible for ENERGY STAR certification.
   • Exterior storm windows without weep holes or other features that allow moisture to drain from between the storm window and primary window.
   • Storm windows that are intended for non-residential buildings.
   • Storm doors.
   • Partial components of an exterior or interior storm window.

Learn How a Product Earns the Label

Storm Windows Key Product Criteria: ENERGY STAR

ENERGY STAR Storm Windows Final Version 1.0 Specification (PDF, 398 KB)