Windows and Storm Windows


Improving the performance of your windows is an important part of an ENERGY STAR Home Upgrade because it reduces the energy waste associated with a leaky home and improves comfort. Windows and storm windows that earn the ENERGY STAR label meet performance criteria that are better than basic building code requirements and vary by climate.

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Windows have many uses in your home from adding light to making your home more visually appealing. However, old, poorly made, drafty, or degraded windows can waste lots of energy and leave you very uncomfortable when weather is the most extreme.  Here are a few big indicators that it may be time to replace your windows.

Understanding Window Replacement Basics

Reasons to replace

Any of these major problems could be a good reason to replace your windows.

  • Single-pane windows (windows with only one layer of glass) – These windows are poor performers at insulating against cold weather and typically do not have coatings to block solar heat in the summer, increasing air conditioning costs. Single-pane windows are big energy wasters.
  • Windows with air leaks or drafts and degraded sills and sashes – These windows also waste energy and are very uncomfortable to sit next to when it is cold and windy out.  Degraded windows can also leak water into your walls causing more problems and allow insects and other pests to enter your home.
  • Windows that do not open or are painted shut – Windows that do not open prevent you from enjoying fresh air on a nice day or a cool evening after a hot day which can reduce energy costs.  Windows that do not open are also hard to clean and maintain.

Other Considerations

  • How many windows do you plan to buy? - To get the best price per window, it helps to plan to buy at least 10 windows to reduce installation costs.  Window installation costs are lower for the contractor if they come to your home for a larger project because of the time it takes to haul the windows to your home, set up the site, and clean up the site.
  • Was your home built before 1978? – If so, the installer will likely have to take precautions due to possible lead paint.  Following lead paint clean-up protocols is good for your home because they require the installer to catch any lead paint chips that fall during removal of the old windows, to clean up the site with extra care when the job is completed, and to dispose of the old windows correctly. The US EPA has excellent guidance on lead paint issues here.
  • Talk to neighbors or friends who have had their windows replaced recently.  Ask around to find leads on good contractors who sell a good windows product, provide product performance details, do not use pressure sales tactics, communicate well, have a good warrantee, and are clean and respectful during the installation.
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ENERGY STAR windows come with a label indicating where the product is certified for. ENERGY STAR ratings vary depending on the climate where you live so you get the right balance of comfort and savings.  Here are some key window performance parameters to consider before you shop.

Window Performance

Key Window Performance Parameters

If you are considering buying new windows, it is important to choose ones that make sense for your climate. While some windows are better at keeping you warm in the winter, others help reduce air conditioning costs in the summer. Some windows balance heat and cold for climates in the middle of the country. Here are some parameters to consider:

U-factor – A measure of the insulating power of a window.  The lower the number the more the window will insulate.  Therefore, a window with a low U-factor is better for cold climates to keep the heat inside.  The U-factor range for windows is typically between 0.15 and 0.50.

SHGC (Solar Heat Gain Coefficient) – A measure of how much solar heat from sunlight is blocked by the window.  The lower the number the more heat is blocked. Therefore, a window with a low SHGC is better for hot, sunny climates, where blocking the heat entering the home will reduce air conditioning costs. The SHGC range for windows is typically between 0.15 to 0.60.

Every ENERGY STAR window is independently certified and verified to perform at levels that meet or exceed energy efficiency guidelines set by the U.S. Environmental Protection Agency.

You can see the current guidelines by climate zone for ENERGY STAR certified windows here.

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There are a variety of window types available for homes.  Here are some things you should consider to help you decide which windows you’ll choose for your home.

Decide Which Type Of Window You Want

Before you call any contractors or installers, it is good to have an idea of what you want.  Here are few things to consider before talking to any sales folks:

  • Energy Performance - If you live in the Northern part of the U.S., ENERGY STAR recommends lower U-factor windows (0.27 and less) which saves energy in cold weather because they insulate better.  If you live in the South, look for lower SHGC levels (0.25 and less) which block more solar heat to keep your house cool in the summer.
  • Frame Material:   Do you want traditional wood or a lower maintenance material like vinyl or fiberglass?  Do you want to paint the window after it is installed, or do you want it pre-finished?
  • Color: What color do you want inside and out?  You can even have one color outside and a different color inside.
  • Grids or Grilles:  Grids today often come between-the-glass, making the windows much easier to clean.  Some companies offer grids that clip on the interior of the window to give a more traditional look to the window from the inside.  Some companies also offer the traditional multi-pane window with each lite being a separate unit of 2 layers of glass.
  • Window Opening Style:  The most common type in the Eastern U.S. is a double-hung window, also called a vertical slider.  On the West coast, horizontal sliders are common.  There are also window types that project out, often opening with a crank, known as casements, awnings, and hoppers. They open from the side, bottom, or top respectively. Fixed or picture windows do not open at all.

There are 6 common window operator types:

window types

Source: U.S. Dept of Energy

For more information on window types and how they work, check out the U.S. Department of Energy’s Window Types and Technologies website and the Efficient Window Collaborative website.

It is a good idea to look at a few company’s websites to see some styles and colors before talking to a salesperson.  When setting up an in-person sales visit, ask what product lines the company sells so you can research them ahead of time.

Talk To A Salesperson

Replacement windows are sold either through a window installation company salesperson who comes to your house, or through a dealer/retailer where you choose the contractor/installer and the windows independently.

Here are some things to discuss with a salesperson when purchasing ENERGY STAR certified windows:

  • Ask for ENERGY STAR! Tell the salesperson you are interested in product models that meet the ENERGY STAR criteria in your location.
  • Ask the salesperson to bring a sample of the product you are interested in and a color palette of sash and frame options.
  • Ask the salesperson for the exact U-factor and SHGC of each window you are considering buying. Reputable companies should be able to provide this information easily. Remember, if you live in the North you are generally looking for windows with a U-factor that is 0.27 or lower and if you live in the South you are generally looking for windows with an SHGC that is 0.25 or lower. For more details, check out the ENERGY STAR windows website at and click on the bar for “Buying Guidance”. NOTE: ENERGY STAR does have equivalent energy performance options for Northern Zone products. See the ENERGY STAR criteria for details.
  • Ask about the window product warranty and the installation warranty. The warrantees can have different time periods for different parts of the window. A decent residential window product warranty should be at least 10 years and preferably 20 years or ‘lifetime’, however that is defined. The glass seal warranties should be at least 10 years and preferably 20 years. Typically, wood finishes and installation warranties are less than 5 years.

Signing a Contract

Here are some things to remember BEFORE signing a contract:

  • Do not sign any document unless you are ready to buy the windows. It is not wise to sign a contract if the salesperson says to "just sign the document and you can always cancel in a day or so."
  • Be sure that any contract you sign for windows clearly states that: “The windows to be installed in the home are ENERGY STAR certified for the installation location.” We see many companies tricking consumers by installing windows that are ENERGY STAR certified – but for the wrong climate zone. Check your climate zone here.
  • Ask that the exact U-factor and SHGC of each window you plan to buy be included in the contract.
  • Try to avoid same-day signing specials. Reputable companies will give you a cost estimate that is good for at least 30 days to allow you time to review and consider their offer.
  • Make sure you are clear that that each window to be installed must have an ENERGY STAR label and an NFRC label with the performance attached.

On the day of installation

Here are some actions to take on the day of the installation:

  • When the installer arrives, the first thing you should do (before any of your current windows are removed) is to check if the windows to be installed are the ones you ordered and that they include both ENERGY STAR and NFRC labels. This may mean cutting or unwrapping each window to see the labels attached to the glass surface.
  • The installer should be told explicitly to keep each window’s NFRC label for you (basically a big sticker) so you have an exact record of what was installed. You may need that record to qualify for utility incentives or for Federal Tax credits.
  • Remember, if your home was built before 1978 and the original windows are replaced, the installer should follow lead paint protocols during the removal of the old windows to ensure lead paint chips and dust are not spread around your house or outside on the ground.
  • Before the installer leaves, open and close each window to ensure they are not twisted or installed unevenly. Casements should crank open easily and vertical and horizontal sliding windows should slide easily. Inspect the caulking on each window to be sure there are no gaps, and all the work is neatly done.

Tip! It is typical for high-performance windows to take 6-8 or even 12 weeks to be delivered after ordering. Windows are made-to-order and require custom built products.

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Upgrading to ENERGY STAR certified windows lowers household energy bills by an average of 12%, but window replacements can be expensive. There are several ways to help reduce these costs. Learn more about financial incentives that may be available to you.

How Cost Effective Is Window Replacement?

Windows are one of the more expensive things to replace in your home. Replacements start at about $400 per window for a simple, yet energy-efficient 3 ft. by 5 ft. double-hung window including a good installation. The upper end of the cost range for the same product is about $1600 per window or more for premium options like specialty wood finishes, historically accurate designs, laminated glass for impact resistance, or extra-strength frames. With that wide of a price range, here are few things to consider:

  • Not only does upgrading your windows save energy, it improves home comfort and increases the value of your home. So while new windows may not pay for themselves in energy savings alone, you can recoup much of the cost from a higher value home sale. It is typically cost effective to upgrade windows to ENERGY STAR certified models which save more on energy bills. 
  • It is important to understand that just because a window is expensive does not mean that the window is energy efficient.  Again, the salesperson should supply you with the U-factor and SHGC performance parameters of each window brand you are considering to better help you compare products. Reputable sales staff should answer all your performance questions and document them in your sales agreement.
Financial Incentives

Rebate Incentives

Rebates for air sealing and insulation may be available through your local utility company. Check the web site of your local utility and visit the ENERGY STAR Rebate Finder and enter your zip code to see what incentives are available in your area.  You can also check with your contractor to see if they know of incentives or rebates in your area.

Federal Tax Credits

There are currently federal tax credits for the cost of purchasing ENERGY STAR windows, and skylights for 30% of the cost up to $600. Exterior windows or skylights must meet the ENERGY STAR Most Efficient criteria. This tax credit is available through December 31, 2032. Learn more about this tax credit

Assistance for Low-to-Moderate Income Families

The Department of Energy (DOE) offers a Weatherization Assistance Program (WAP) available for households with lower incomes that qualify for Supplemental Security Income, Aid to Families with Dependent Children, and other income eligibility criteria. This program includes a home energy assessment and common home improvements such as repairing windows or replacing a few damaged windows – but generally do not replace a whole house full of windows.  Some programs also offer storm windows.  You can also contact your local electric utility to see if they offer energy efficiency home upgrades for low-income customers.

A More Affordable Option - Storm Windows

ENERGY STAR certified storm windows are an affordable option for homes where full window replacement may be difficult, such as lower-income households, low-rise multi-family households, households working with HUD or weatherization programs, or households in historic preservation districts.

ENERGY STAR certified storm windows use “low emissivity” or low-e glass to improve the energy performance of your home compared to clear glass storm windows. ENERGY STAR certified storm windows are designed to allow the right amount of solar heat through your windows to keep your home cool in the summer and warm in the winter, and help you save on energy bills. 

How much can I save with ENERGY STAR Storm Windows?

EPA estimates that on a national average, ENERGY STAR certified (low-e) storm windows can save homeowners about 20% on their annual heating and cooling bills when installed over single-pane clear glass windows (without existing storm windows). You can expect to pay back the incremental cost of the ENERGY STAR certified storm windows in about three (3) years. 

Consumers who already have clear glass storm windows over their single pane windows and replace the storms with ENERGY STAR certified (low-e) storm windows can save an additional $50 per year on heating and cooling (about 2%) on a national average.

Additional Benefits of Modern Storm Windows:

  • Can be installed on the interior or exterior of an existing window.
  • Cost ½ to ¼ the amount of common replacement windows with much lower cost installation.  They can also be Do-It-Yourself installed without training in a few minutes to save even more money.
  • Come in both fixed and operable (open and close) options and with insect screens.
  • Come in a variety of colors to match your home.
  • Can be purchased conveniently at many home improvement stores and can be specialty manufactured to perfectly fit to your current windows. 
  • External storm windows are designed with weep holes to manage moisture while also controlling air leakage.
  • ENERGY STAR certified storm windows have high-gain low-e coatings for Northern climates to optimize solar gain when it is cold.  ENERGY STAR storm windows for Southern climates are designed to block solar gain because they are low-gain, low-e, which helps to lower air conditioning costs.