Windows come in a variety of different sizes, functionality and building materials, coming from an amazingly wide array of manufacturers. Choosing the best window for your home can be a daunting task with the plethora of data available.

However, the most important – and overlooked – quality of a new window is how well it saves energy.

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While buying the cheapest window on the market may be good on your checkbook at first, it can eat away at those savings in a hurry if the window is not meant for your home’s climate. Windows are notorious for leaking air and heat, and as energy costs continue to rise, this can cost you thousands over the course of a couple of years. has analyzed thousands of data points to find the best windows for your area.

The Use of Climate Zones

The US Department of Energy (USDoE) has broken the United States up into eight major climate regions, with additional sub-regions based on average rainfall.

Every three years, the IECC map is adjusted to move certain counties into and out of different climate zones. The latest was released in 2021. These climate zones are used to determine recommended energy-saving qualities of windows. The minimum values of U-Factor (heat loss), SHGC (solar heat gain), Air Leakage and others for each climate zone are set by the USDoE.

This means that depending on your climate region, it may not make sense to simply buy the most efficient window on the market. The added cost of a more energy-efficient window may be wasted if your local climate is mild, such as many of our southern states.

Conversely, northern “colder” states may see their energy costs rise if their windows do not meet or exceed recommended values. It is very possible that the cost savings earned by buying cheaper windows will be eaten up by increased energy costs.

Understanding the NFRC Window Label

The National Fenestration Rating Council (NFRC) label helps you compare between energy-efficient windows, doors, and skylights by providing you with energy performance ratings in multiple categories.

While ENERGY STAR labels just tell you if a product is energy efficient or not, NFRC labels tell you how efficient they actually are. The different climate regions within the United States have specific ranges each of these values need to fall in between to be considered energy efficient.

The NFRC certifies that each window that carries its label has undergone independent verification by an accredited lab.

U-Factor measures how well a product can keep heat from escaping from the inside of a room. The lower the number, the better a product is at keeping heat in.
Range: 0.20–1.20
Look for: Low numbers

Solar Heat Gain Coefficient (SHGC) measures how well a product can resist unwanted heat gain, which is especially important during summer cooling season. The lower the number, the less you’ll spend on cooling.
Range: 0–1
Look for: Low numbers

Visible Transmittance (VT) measures how well a product is designed to effectively light your home with daylight, potentially saving you money on artificial lighting. The higher the number, the more natural light is let in.
Range: 0–1
Look for: High numbers

Air Leakage measures how much air will enter a room through a product. The lower the number, the fewer drafts you’ll experience.
Range: ≤ 0.3
Look for: Low numbers

Condensation Resistance is an optional value for manufacturers to include, and measures how well the window resists condensation.
Range: 0-100
Look for: High numbers

An example window NFRC sticker
Window Energy Loss (Courtesy US Dept. Energy)

Potential Energy Savings

One study in 2012 done by the National Center for Preservation Technology and Training found that replacing your old, leaky single pane windows with new high-performance ones resulted in home energy savings ranging anywhere between 18-29%. Lower quality windows provided fewer savings. Colder cities such as Chicago and Boston saw greater savings than warmer cities like Atlanta.

The study also found that if replacing your old windows is not an option, adding weatherstripping, insulated cellular shades or interior window film resulted in anywhere from 5-15% savings.

To put some of these percentages into actual money saved is difficult. Each part of the country has its own energy costs, climates and window availabilities. However, in the same study referenced above, replacing a whole house with new high-performance windows saved the average homeowner anywhere from $380 to $780 per year!

Types of Windows

We wouldn’t be honest with ourselves if we thought everyone bought their new windows based solely on its energy-saving properties. In this section, we explain the differences between the various materials the windows are made from as well as the different functionality you can expect to find across the different product lines.

The amount of options in windows can be overwhelming. We help break down the pros and cons of each building material and fea

Window Building Materials

Most windows are built with casings made from ether vinyl, fiberglass, wood or aluminum.

Vinyl Window Cross-section

Vinyl is a window with a plastic casing, and tends to be the cheapest of the bunch. The trade-off is that it is a poor insulator, which will cost you more in future energy bills. Vinyl windows almost always comes in white (inside and out), but sometimes you can find the outside casing painted a different color. Most replacement windows and the “buy one, get one” deals are for vinyl windows as they are the easiest and cheapest to build and/or customize.

Pro: Cheapest Option, Most Widely Available
Con: Poor Insulator, Not Durable

Fiberglass Window Cross-section

Fiberglass windows are commonly very durable, and are made of intertwined glass fibers glued together with a hard resin. Fiberglass window frames won’t damage easily, and are resistant to dents, scratches, warping and corroding. These windows are manufactured to withstand extreme heat and cold, so they don’t expand or contract as the weather changes. Also, fiberglass is an insulator. This means they absorb and hold heat, maintaining the comfort levels inside your home in the winter and keeping out the high temps in the summer.

Pro: Good Insulator, Durable
Con: Few Color Choices, More Expensive than Vinyl

Wood Window Cross-section

Wood windows are generally regarded as the most ascetically pleasing windows, but they also have great insulating properties. Wood windows insulate the best out of all building materials, however the main drawback is the fact that wood is destructible. Whether it is pets, kids or condensation, wood windows can show the wear pretty easily if not cared for.

Pro: Great Insulation, Looks Good, Can be Painted
Con: Not Durable

Aluminum Window Cross-section

Aluminum windows are most commonly used in commercial applications as they are by far the most durable of all the options. Aluminum is also commonly used as the outside flashing on many wood windows.

Pro: Extremely Durable, Available in Any Color
Con: Expensive

Window Operational Types

The two most common operational window types is Casement and Double-Hung. There is also the non-operational static or Picture window, which does not open. The other types that are less common include Awning, Bay, Sliding, and Single-Hung.

Casement window hinges can be situated either on the top or side, allowing the window to swing out left or right, or to the top. All casement windows open to a 90-degree angle and have a handle that rotates to swing the window outwards.

Double-Hung windows (or commonly called sashes) slide either up-and-down or left-and-right, and are commonly moved with tracks and springs that are embedded in the frame.