Energy Efficient Windows Buying Guide

How to Buy Energy Efficient Windows

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If you’re like many Americans, every month that your energy bills have climbed yet again, you stop to wonder how much of your money is literally going out the window. While many factors influence the overall energy efficiency of a home, windows are among the most common culprits for energy leaks. Whether they were improperly installed, have suffered damage or deterioration, or are simply outdated in their construction and technology, installing energy efficient windows can help you realize significant savings over time.

ENERGY STAR Window Ratings

Among the first things you might notice when shopping for replacement windows is differing Energy Star certification ratings, typically displayed on a sticker on the window glass. Energy Star is a program managed by the U.S. Environmental Protection Agency (EPA) and U.S. Department of Energy (DOE), whose goal is to provide important information about how much energy the usage of different devices and products commands. These ratings are found on many energy-efficient products in homes, industrial plants, and commercial buildings that have met a specific standard of efficiency.

What makes a window energy efficient infographic


The specifications that must be met to earn an Energy Star certification vary, with some items naturally demanding more or less energy than others. Even within windows themselves, the requirements differ by region, as our climates and the natural elements we’re up against are vastly different across the nation. To determine the numbers you’ll see on Energy Star windows, they are independently tested by the National Fenestration Rating Council, or NFRC.

NFRC Ratings – Performance Across 5 Categories

When looking at the Energy Star ratings on windows, you’ll notice 5 distinct scores. These represent the findings of the NFRC as they relate to 5 separate energy-efficiency category tests. Let’s explore each:

  1. U-Factor: While it might sound like a hip new singing competition, the U-Factor is a measure of your window’s insulation abilities. This is determined by measuring the rate of heat transfer. Measured in Btu/h·ft²·°F, the typical range for these values is 0.25 to 1.25, with lower numbers reflective of better insulating windows.
  2. Visible Transmittance (VT): This measures how well windows perform one of their most basic functions – effectively letting the sunshine in! While this is an important consideration for a variety of reasons, it is included in an energy-efficiency checklist because of its ability to reduce your reliance on energy-consuming artificial lighting during daylight hours. A higher number is more desirable for VT.
  3. Solar Heat Gain Coefficient (SHGC): This measure is reflective of how well a window resists unwanted heat gain – one of the most important factors in determining what you can expect from your cooling bills in the summer. Energy Star compliant windows in the Mid-Atlantic region require an SHGC score of .40 or less – the lower, the better. Thompson Creek’s double-hung replacement windows far exceed this requirement, with an impressive SHGC of just .21. This is accomplished in part through the inclusion of argon gas between the glass panes. Learn more about Solar Heat Gain!
  4. Air Leakage: This is the test those rattling, drafty old windows would be sure to fail – a measure of how much air windows will allow to pass through. With a range reported as ≤ 0.3, you’ll want to look for lower numbers for this category, as those reflect better protection against drafts and leaks.
  5. Condensation Rating: The only rating of the 5 that is optional for manufacturers to include on the window label, this is reflective of a window’s ability to resist condensation. A higher number is more desirable for this rating, as that indicates superior resistance to condensation build-up.

All of Thompson Creek’s energy efficient replacement windows exceed the current performance criteria requirements for Energy Star Certified windows within the Mid-Atlantic climate zone. We are committed to working with the best materials to design beautiful, strong, safe windows that will enhance your home for decades to come.

How Much Do Energy Efficient Windows Save?

Many factors influence how much you can save with replacement windows including the following: 

  • The age and condition of the windows you’re replacing
  • Whether you’re replacing single-pane or double-pane windows
  • How many windows you’re replacing, and their sizes
  • How well your walls and/or attic are insulated

Return on Investment (ROI)

It is important to consider cost benefits beyond those recognized through reduced energy consumption alone. In example, you may find you have to replace furniture and carpeting less often as it is better protected against fading from incoming sunlight. Additionally, you will be increasing the value of your home, helping you recoup some of the cost if you decide to sell.

While many home upgrades don’t have a significant impact on the resale value of a home, replacement windows are among the most important considerations homebuyer’s make. In fact, studies have shown that you can expect greater than a 70% return on investment for vinyl replacement windows in the Mid-Atlantic. To put that into perspective, an upscale master suite addition will only net you a ~46% ROI, on average.

Can You Get a Tax Credit for Energy Efficient Windows?

To support citizens in making energy-efficient choices in upgrading their homes, the IRS has historically offered certain incentives – also commonly known as tax credits, or tax rebates. Because the specifics and requirements of these energy incentives are updated regularly, we recommend visiting for the most up-to-date information and program expiration dates.

As of the time of this writing, the currently available Nonbusiness Energy Property Tax Credit entitled homeowners to up-to a $200 rebate for installing energy-efficient windows, with a $500 lifetime credit cap for window and door purchases.

Energy star certified replacement window savings infographic

Window Glossary Terms You Should Know

For energy-efficiency research in particular, two terms you’ll likely see referenced often are “window glazing” and “low-e glass.” Below we explore the ins and outs of each of these window terms:

Window Glazing

  • Glazing is a term that applies to the invisible coating on energy-efficient windows. Thompson Creek replacement windows are manufactured with a high-quality, low-e glaze, explored in more detail below.
  • When you’re buying new energy-efficient windows, the glazing is done in the manufacturing process; this isn’t something applied after installation. However, many people opt to have old, existing windows in their home re-glazed, or in some cases, glazed for the first time.
  • Opting for re-glazing instead of replacing old windows is typically a choice of homeowners who are looking to preserve as much of the original home as possible in their upgrades.
  • While new vinyl windows would offer better insulation than re-glazing existing windows, the latter is often chosen to maintain the original design, or because the homeowner has placed a higher importance on retaining original materials.
  • Oftentimes, it is also a situation where the existing window is a unique, customized shape, or would be very difficult or impossible to replicate, such as a stained glass window.

Low-E Glass

  • Commonly abbreviated as “Low-E,” which stands for low-emissivity,  low-e glass has received an invisible coating designed to increase the energy-efficiency of your windows.
  • Think of low-e glass as a heat mirror that functions as though it were facing your home in the winter, and facing away from your home in the summer.
  • To keep you cozy and warm in the colder months, low-e glass reflects heat back into your home.
  • When the August sun is blazing down, it helps to keep your cooling bills in check by reflecting heat away from your home.

Professional Replacement Window Installation

Thompson Creek worker installing window on brick house

New windows are a major home investment that requires expertise from start to finish. Professional window manufacturers and installers like Thompson Creek have years of experience to inform our perfected process. We have encountered every “unexpected problem” you can think of, and refined the solutions to solve for them before they even happen.

We understand the importance of saving wherever and however possible when renovating your home, and appreciate that there are plenty of opportunities where putting in some extra time, sweat, and elbow grease of your own is essential. However, there are some projects better left to professionals, and window installation is one of those projects. You don’t want to risk jeopardizing the money you’ve invested on quality window replacements by inadvertently making costly installation mistakes, some of which you might not realize until the next major rain or snowstorm. Have it done right the first time, and you’ll reap the rewards for decades to come.  Proper window installation is critical for you to realize the true benefits of new windows.

Window Frame Material Options

What is the best window frame material for your home? At Thompson Creek, we offer vinyl replacement windows, the style we believe to be the best choice for durability, insulation, ease of maintenance, and more. Within our Window Frame Types blog post, we explore some  of the top considerations to make for each of the most common window frame materials to help in making an informed choice.

3 Other Benefits of ENERGY STAR Windows

Multiple windows surrounding seating area in house

  1. Protection Against Damaging UV Rays – Whether you’re washing dishes at the kitchen window, playing with the dog on the sun porch, or catching up on some work at your desk with the blinds open, something you might not be thinking about is the harmful UV rays hitting your windows. With Thompson Creek’s Low-e glass replacement windows, you can carry on with your day without worry. The same coating that helps make your home more efficient is also designed to block UV rays, protecting you and your family.
  2. Furniture & Flooring is Protected Against Fading – That same UV light that can be harmful to you and your family also leaves its mark on carpeting, furniture, and other flooring materials. While a sun-faded doormat might have a certain charm, the same cannot be said for sun-damaged couches, chairs, or expensive rugs. To add insult to injury, the fading is often uneven, as the sun hits different areas with varying intensity. This can leave homeowners frustrated with having to make costly replacements to items that are still in otherwise good condition. The invisible coating on energy-efficient windows helps to greatly minimize fading so you can place your furniture, area rugs, and even artwork exactly where you wish, without having to account for its window proximity.
  3. Ease of Cleaning – Thompson Creek’s best selling double-hung windows make cleaning a breeze. Gone are the days of trying to slide your arm up to reach the outside from the inside, fearing the window would break or come crashing down on your hand with each hasty swipe of the cloth! With a top window sash that can be lowered, and a bottom window sash that can be raised, you can simply adjust each to a comfortable height for cleaning, and tilt them in toward you. Each sash can also be locked in place to increase safety, or removed completely in the event of an emergency, or to aid in bringing oversized items into or out of a room.

Enhanced Style, Safety & Comfort

Because all of Thompson Creek’s replacement windows are Energy Star Certified, you can choose whichever best matches your personal style without any compromise on efficiency. In addition to the more practical benefits of energy efficient replacement windows, like cost savings and environmental responsibility, having new windows in your home also comes with plenty of equally important benefits to your everyday comfort and enjoyment of your home.  

Rearrange Your Furniture: Did an old, drafty window prevent you from putting the couch where you ideally wanted to? With Energy Star replacement windows, you no longer have to consider the “chill factor” in your interior design. You also don’t have to worry about your favorite painting suffering damage from the sun, so go ahead and hang it above the mantel where it can truly shine.

Open the Blinds: Many homeowners who have been frustrated with drafty windows for years might not even realize that they’ve allowed it to stop them from fully opening the blinds or curtains. With your beautiful new windows in place, it’s time to let the sun shine in! Bathe your home in rejuvenating light, and watch your spirits lift right along with it.

Enjoy Greater Peace of Mind: Even if we’ve taken all other reasonable security measures, it can be difficult to feel completely safe in a home with damaged or outdated windows that can be easily broken or otherwise bypassed. Thompson Creek’s modern, secure windows can help you rest more easily, a comfort you can’t put a price on.

Energy Efficient Curtains & Blinds

Once your replacement windows are installed, you can boost their efficiency even further with energy saving curtains and blinds. To maximize their effectiveness, these window coverings are installed as closely to the window frame as possible. This helps to create a seal, effectively reducing heat loss in the winter, and reducing heat gain in the summer. Think of these as a two-sided shield that acts as an extra level of protection in harmony with your energy-efficient windows.

While installation provisions can be made to most curtains and blinds to increase their energy efficiency, there are designs manufactured with this consideration in mind:

  • Energy saving curtains, commonly referred to as thermal curtains, feature two to four layers of fabric with an overlapping center for a tighter seal.
  • While their often-heavy construction may make them seem like a winter-only fix, they can help keep your home cooler in the summer as well by reflecting light away from your home, much like low-e glass.
  • Among the most energy-efficient styles of blinds available are cellular blinds, also known as honeycomb blinds.
  • For optimal insulation, look for larger pleat sizes, and double or triple cell designs.

We hope we’ve helped better inform your decision by exploring the myriad ways energy efficient windows make a bright choice for your home, and which considerations to make. Not only can they help you realize long-term energy savings with a reduced environmental impact, but they also increase your home’s beauty and values. Contact us today for a free estimate on your replacement windows!

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