About Energy Star

In Canada and the United States, ENERGY STAR is the certification system used to identify energy-efficient products such as windows and doors. The ENERGY STAR symbol indicates that a product has met or exceeded certain standards after being tested by an independent laboratory.

Having a single set of standards makes it easier for consumers to compare products. However, those standards occasionally change to keep up with evolving technology or environmental policies, so you should always ensure you’re referring to the latest figures.

It’s also important to note that not all ENERGY STAR products offer the same level of energy efficiency. To understand the differences, take a closer look at the individual performance markers.

U-Factor / U-Value

U-factor, often called U-value, is a measurement of a product’s resistance to heat loss. Windows with a lower U-factor provides better insulation, and as a result, they don’t let as much heat escape in comparison to windows with a higher U-factor. Choosing windows with a low U-factor is particularly beneficial during the colder months, as they don’t need to compensate for heat loss.

Solar Heat Gain Coefficient (SHGC)

Solar heat gain coefficient (SHGC) refers to the amount of solar radiation transmitted through a window and into a home or building. SHGC will appear as a number between 0 and 1, with a lower number indicating that the window transmits less solar heat.

The type of glass plays a significant role in determining SHGC. Low-E glass typically reduces solar heat gain with its protective coating, which can help control air conditioning use during the summer. However, windows with a higher SHGC may be desirable depending on the climate, the room’s orientation and the level of surrounding shade. Get in contact with your contractor or a window dealer about finding the perfect solution for your space.

Visible Transmittance (VT)

Visible transmittance refers to the amount of visible light allowed to pass through a window. A lower number is a result of a lower amount of light entering the home—typically seen homes with Low-E glass windows, as it is constructed with a special coating that reduces solar heat gain. The highest quality Low-E glass windows can achieve a comfortable balance—letting in sufficient amounts of natural light, while minimizing unwanted heat gain.

Air Leakage

Air leakage is a measurement of the amount of air that passes through cracks in a window. A higher rate of air leakage indicates the window is more susceptible to heat loss and gain, which reduces energy efficiency and interior comfort.

Air leakage can also result from improper installation, especially if it occurs around the frame.


R-value is often mentioned in relation to U-value, seeing as both are reflections of the same process. Whereas U-value refers to the rate of heat loss through a window, R-value refers to the window’s ability to retain heat. An energy-efficient window should have both a low U-value and high R-value.

Energy Rating (ER)

This figure captures the overall energy-efficiency score of a window. It encompasses U-factor, air leakage and SHGC, giving consumers a more convenient way to compare products. The standards for energy ratings vary according to climate zone. To earn the ENERGY STAR label in Canada, a window must have a minimum energy rating of 25 in zone 1, 29 in zone 2 and 34 in zone 3.

Clear Glass

Clear glass unit provides more efficiency on noise protection than a single pane glass. A clear glass unit allows heat and cold air from both the inside and outside to pass through without resistance.

Low-E Glass

In winter, Low-E Glass reduces hear loss to cold outdoors, by dramatically reducing radiant heat transfer and actually reflecting interior heat back into the room. It allows more of the sun's rays to enter a home as solar energy to be converted into usable heat inside, and in the summer it helps to reduce the flow of hot outside air into the cooler interior, therefore, it helps to lower your energy costs all year long. Low-E Glass also reduces transmission of the sun's UV ray which is the leading cause of premature fading and degradation of fabrics and flooring.


LoE-180 is the perfect cold remedy. Ideal for passive solar applications, it allows winter sun's heat to pass into the building while blocking heat loss outside. In a double-pane glass unit with argon fill, Cardinal LoE-180 glass delivers an ER of 45, U-factor of 0.26 and visible light transmission of 77%.


LoE(2)-272 is ideal for any climate, any weather. Just look at the numbers. In a double-pane glass unit with argon fill, Cardinal LoE(2)-272 glass delivers and SHGC of 0.40, U-factor of 0.25 and visible light transmission of 70%


Just look at the numbers. In a double-pane glass unit with argon fill, Cardinal LoE(3)-366 glass delivers a SHGC of 0.27, U-factor of 0.24 andvisble light of 63%.

Argon Gas

Argon gas is denser than air, adding it to the captive air in double-pane windows improves thermal insulation efficiency. Use with a special low-E glass coating, argon gas windows bring the temperature of the window closer to room temperature. This process ultimately eliminates air currents and drafts that occur when differing temperatures meet.

Triple Glass

Triple pane glass windows are the most energy efficient models in the market, due to the extra pane of glass, insulating glasses help keep cold air outside and warm air inside, or vice versa. Special coating are often applied to the glass windows to enhance their energy efficiency by eliminating solar gain.

Super Spacer

Warm edge technology is more than just a low-conductive product that helps make windows more thermally efficient. The warm edge spacer is the actual seal that keeps the glass package in windows from failing.

There are two type of insulating glass systems on the market today. Single seal and dual seal systems. Single seal units are constructed of only one type of sealant, which is called upon to perform double-duty. Not only must the sealant retard the infiltration of moisture vapor, but it must also hold the unit together under a wide variety of both high and low humidity and ultraviolet exposure.

A duel seal unit is constructed using a combination of a sealant that functions mainly as a high strength adhesive and a second sealant, which is used primary as a moisture seal.

Super Spacer is a dual insulating glass system. This NO-Metal, structural foam spacer clearly resists condensation, energy costs, provides long life durability and adds both comfort and value to your windows.

The all foam formula of Super Spacer is proven to be less conductive, which can block heat from escaping or entering through the glass edge. It provides optimal thermal performance and is the lowest U-value in the industry.