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Ultimate Guide to Energy Efficiency Ratings for Windows (2024)

Planning to replace your house windows? Gone are the days when it was all about aesthetics; energy efficiency is equally important. Nowadays, homeowners are looking for ways to reduce their heating and cooling bills while maximizing the return on investment. 

Not only do the energy-efficient windows keep your home pleasant in the hotter and colder months throughout the year, but they will also save you money by lowering your home’s energy consumption!

But with many factors influencing how comfortable and energy-efficient your home is, it’s easy to feel overwhelmed by things like window performance, standards, and features.

Don’t worry! This post will provide detailed insights into the factors that must be considered when choosing energy-efficient eco windows

What Makes a Window Energy-Efficient?

The easiest way to understand whether your windows bear the modern standard of energy efficiency you may refer to the number of panes the units have. Simply put, a window pane, also known as glazing, is the sheet of glass that separates the inside of your house from the outside.

The two most common types of energy-efficient windows are:

  • Double pane windows
  • Triple pane windows

As the name suggests, double pane windows come with two panes, while triple-pane windows contain three panes.

These windows come with different ratings, and much technical information is involved. Therefore, it’s better to do your homework and find the ideal window specifically for your requirements.

Keep reading to learn more!

Benefits of Energy-Efficient Windows 

The most obvious and direct benefit of energy-efficient windows is the money you save on heating or cooling your house. HVAC systems work to cool the air by removing moisture from the air and circulating it, letting it accumulate inside your house.

Heating works the same way, the less air that escapes, the less heat is needed to maintain a comfortable living space. Energy-efficient windows stop air from escaping, so your system has to work less, saving you money on electricity.

By using less energy, you reduce greenhouse gas emissions at power plants and reduce your own carbon footprint.

Being energy efficient doesn’t just mean saving on heating or cooling costs; there are other impacts on your home that save you money in other, less obvious ways.

One aspect that often gets overlooked when it comes to saving money is retaining or increasing the value of a house. From being more resistant to window breakage, to letting in fewer UV rays, which can fade the color out of your floors, furniture, and carpets, and even cause permanent damage to wood, like drying, fading, and cracking.

This kind of damage lowers the value of your interiors and your furniture and can be very costly to restore. Energy-efficient windows stop more UV rays than normal windows, keeping the value of your house up.

Another benefit of energy-efficient windows is the prevention of condensation, which can stain windows and walls, and eventually cause mildew, bringing down the value of your home.

The pockets of air between double and triple-glazed windows also reduce outside noise by up to 70%, which is great if you live in a city center or busy neighborhood.

Everything You Should Know About Energy-Efficient Window Ratings

If you want to install an energy-efficient window to boost your house value and comfort, it is essential to know which standards and ratings your replacement windows should have.


The R-value is a measurement of your window’s thermal resistance. It is a rating system for determining a window’s total insulating value.

The higher the R-value, the better insulator your windows will be! The R-value of double pane windows ranges from 3 to 3.8. On the other hand, triple-paned windows provide an R-value of 5, making them more efficient in blocking heat flow.

U- Value

The U-value provides a measurement of heat gained or lost through the glass. You don’t want a large amount of heat to escape through your windows. Therefore, the lower the U-value, the more energy-efficient your windows will be!

For modern energy-efficient windows, the U-value generally ranges from 0.20 to 1.20.

Solar Heat Gain Coefficient

The SHGC is a number that indicates how much solar energy is transferred through a window. It shows how well the window blocks heat from the sun.

The higher the number is, the more solar heat can come through the windows. Or, the lower the number, the less heat the window allows. The SHGC is measured on a scale of 0 to 1. You can choose the number depending upon your need. The standard SHCG numbers range between 0.25 and 0.80. 

Energy-efficient windows - image of plants inside a window with sunlight streaming in over them

Air Leakage

As the name suggests, air leakage describes how much air escapes from a window. You obviously do not want your windows to leak a lot of air because that means letting heat (or air conditioning) escape. This will put an extra load on your HVAC system resulting in inflated energy costs. 

The more the air leakage, the less energy-efficient your windows will be. Below 0.3 is considered a good air leakage rating. 

Visual Transmittance

Also known as Visible light transmission (expressed in percentage), Visual transmittance (defined as a number from 0 to 1) is a measurement of the amount of light that passes through the window. For example, 0.5 VT would mean that 50% (VLT) of the light gets through the window. 

The VT value of most double- and triple-glazed windows ranges between 0.30 and 0.70. A higher VT means that your windows transmit more visible light. However, there is often an unwanted solar heat gain along with visible light.

To tackle this, look for high-performance windows with low-E coatings. The E-coating prevents the solar heat gain and allows a high amount of visible light to transmit.

Once you’ve evaluated all of the aspects that make windows energy-efficient, it’s time to order your new windows! But how do you ensure that the product you’re dealing with is of the finest quality and will provide you with the energy efficiency you require?

The quickest and easiest way to tell if a window is energy efficient is to look for the ENERGY STAR logo:

Energy-efficient windows - ENERGY STAR logo
Image Source


Energy Star is a government-backed program that ensures that the windows have undergone extensive testing and have been verified by the National Fenestration Rating Council (NFRC).  

In Northern areas like Canada, ENERGY STAR-certified windows let infrared light into your home and prevent warm air from leaving. These windows are about 20% more efficient than standard windows and can save you around 45% on your energy bill. 

Windows become eligible for Energy Star depending on their U-factor or Energy rating. ER is a combination of U-Value, SHGC, and Air Leakage. The ER rating makes it easier for you to compare the thermal efficiency of windows from various manufacturers.

According to the 2022 ENERGY STAR® Standards, energy-efficient windows should have a U-factor of 1.22 W/m2 or lower or an ER of 34 or higher.

Take a look at this useful video by Ecoline Windows Calgary to understand ER Ratings better:


Popular Window Styles – Which Units are the Most Energy-Efficient?

Today’s window market can offer homeowners many window styles to perfectly complement the exterior, add value, ventilation and overall comfort. But when it comes to energy-efficient properties, now all windows are alike.

Of course, if you strive to get custom windows that are perfect for your house needs, you can go with almost any window style, making it decent in terms of energy conservation by adding extra layers of glass, different coatings and add-ons to boost energy rating.

If we break things down to basic models, the 2 most energy-efficient window styles are:

Picture Window

This one is non-operable, meaning you can’t open or close it. A huge glass area makes picture windows perfect for unobstructed views outside. Homeowners usually install these units for living rooms to significantly boost the thermal performance of their houses without compromising on aesthetics.

Energy-efficient windows - Example of a picture window

Casement Window

As the most energy-efficient window style among operable units, a casement window is a best-seller. These units operate similar to doors, allowing for maximum ventilation. Still, with state-of-the-art sealing technology and high insulating properties, casement windows are perfect for boosting the energy efficiency of your house.

Energy-efficient windows - Example of an open casement window

If you are interested in prices for the two window styles described above, we have prepared a brief breakdown below. Keep in mind, though, that the price range given is not a precise one since window replacement involves far more details than just choosing the style and glazing, however, the following will give you a rough idea of the costs involved:

Window Type Double-Pane, per unit Triple-Pane, per unit
Picture Window $315 – $1890 $375 – $2130
Casement Window $565 – $1134 $620 – $1340

Source: Ecoline Windows

Cost of Energy-Efficient Windows

Windows are generally priced by size and efficiency rating. In simple terms, generally speaking, higher quality windows mean a higher price, but more savings on your energy bill, and the longer the windows will last. 

Installing windows can cost anywhere between $375 to $800 per window, depending on several factors, such as:

  • Brand of windows
  • Contractor costs
  • Type of window
  • Size of the window

Energy efficient upgrades incur additional costs and can increase the cost per window anywhere from 15% – 30%, excluding the cost of labor. Energy efficiency upgrades are not one-size-fits-all either and depend on a few different factors:

  • Type of glass and number of panes (single, double, or triple)
  • Low Emissivity coating type, which helps reflect heat
  • Gas fills, which go between the panes of glass to improve insulation and slow heat transfer
  • Spacers, which go between glass layers to improve insulation
  • Frame Material

There are several government incentives for homeowners who make energy-efficient home improvements, from personal tax credits and grant programs, to rebate programs and loan programs. These programs are widespread and vary from state to state.

A list of incentives can be found on the DSIRE (Database of State Incentives for Renewables and Efficiency) website, which lists energy-efficient incentives by state, category, and incentive type. 

Material Used for Energy-Efficient Windows

The type of material window frames are made of can impact their insulative properties, longevity, and effectiveness in different climates. The 5 materials generally used in energy-efficient windows are:

  • Vinyl
  • Composite
  • Aluminum
  • Fiberglass
  • Wood

Each material offers different benefits and costs. 


Vinyl frames offer low maintenance and provide good thermal insulation and range in price from $250 – $600 per window.


Composite frames are made of various blended materials and offer durability, low maintenance, and good insulation, and range in price from $300 0 $1,100 per window.


Aluminum frames offer durability, and low maintenance, and are a more eco-friendly option as they include recycled material and are recyclable. They range in price from $400 – $1,200 per window.


Fiberglass frames are very strong, durable, low maintenance, and provide good insulation. They range in price from $600 – $900 per window.


Wood frames provide strength, and good insulation, and are more eco-friendly than some other materials. They range in price from $600 – $2000 per window, depending on the type of wood used.

Final Thoughts

Windows replacement is a big decision; therefore, you should purchase new windows with aesthetics, energy efficiency, convenience, ventilation, and other crucial aspects in mind! With window replacement being one of the most payable home renovations based on ROI, getting ENERGY STAR windows will ensure that you are spending your money on high-performance, comfort and energy cost reduction by 45%. 

Frequently Asked Questions

What are energy-efficient windows?

Energy-efficient windows are modern windows with double or triple glazing and LoE coating that aim to drastically reduce the energy bills by providing better insulation and reducing the need for heating and cooling, adding comfort throughout the year. Read the full guide to learn more about energy-efficient windows and how they work.

Which windows are better – double or triple-paned?

Double-pane windows are now a standard among window companies; they are sufficient for regions with adequate weather conditions. Such windows are advised for areas with extreme weather changes or if the overall thermal performance of your house needs a significant improvement. Triple-pane windows may be up to 55% more energy-efficient, but they will also require 15-20% more investment. Read the full guide for more info on energy-efficient windows.

Which window styles are best in terms of energy efficiency?

Picture and casement windows are best when it comes to energy-efficient properties. Read the full guide to learn why these two types of windows are the best styles for energy-efficiency in windows.

References Update or Replace Windows – Energy Saver

ENERGY STAR: ENERGY STAR Most Efficient 2022 — Casement Style  Windows

Government of Canada: ENERGY STAR Windows, Doors and Skylights

The Spruce: What Is a Double-Paned (or Double-Glazed) Window?

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