Energy Efficient Windows

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Energy Efficiency Ratings
Energy Efficiency Ratings
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What does energy-efficient windows really mean?

Saving energy is one of the most important concerns of homeowners. You want to save energy in everything you do to reduce the cost incurred. There are numerous ways of saving energy but most people are not yet well informed. Let’s have a look at energy efficiency from a different angle.

When buying windows, one of the most important consideration should be the energy efficiency ratings. However, energy efficiency information can be overwhelming. To help you make well-informed decisions, here is a compilation of the performance markers that play a key role in determining the energy efficiency rating of windows.

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    Energy Performance Rating

    ENERGY STAR in the United States and Canada

    What is ENERGY STAR? It is the certification system that is used in the identification of energy-efficient products. This certification system is suitable for doors and windows among other products. The ENERGY STAR symbol is placed on a product to confirm that it meets or exceeds certain standards. The symbol is placed after the product is tested by a credible independent laboratory.

    Comparing products without a single set of standards can be a daunting task. ENERGY STAR makes such comparison quite easy. However, these standards may change so as to keep up with the ever changing environmental policies and evolving technology. When comparing products, always ensure that you refer to the most recent figures. It’s worth noting that ENERGY STAR products offer different levels of energy efficiency. Take a look at these individual performance markers to understand the differences.

    2022 ENERGY STAR® Standards

    Windows are eligible for ENERGY STAR® based on their U-factor that measures their overall heat loss, or, their Energy Rating (ER) that combines their passive solar heat gain (SHGC) through the glass with their overall heat loss and air leakage. Models must have a U-factor of 1.22 W/m2 or lower, or, an ER of 34 or higher.

    Caution is advised when selecting windows and sliding glass doors with passive solar heat gain (SHGC) values above 0.45 that will face south or west, especially if there is more glass area than exterior wall area (high window to wall ratio), as this could cause uncomfortably warm room temperatures and higher cooling costs.

    Energy Performance Ratings

    U-Factor Solar Heat Gain Co-Efficient Visual Transmittance
    Energy Rating Air Leakage Energy Level


    Also referred to as U-VALUE.

    U-FACTOR is the measurement of the resistance of any given product to heat loss. Windows that provide better insulation have a lower U-FACTOR. Such windows do not let much heat to escape.

    A higher U-FACTOR means increased heat loss.

    When choosing windows during the colder season, it is advisable to go for those with a low U-FACTOR. With such windows, you will save on your heating bills.

    Solar Heat Gain Coefficient (SHGC)

    Solar heat gain coefficient is the amount of solar radiation that is transmitted into a building through the window. Solar heat gain coefficient is a figure between 0 and 1. A lower number indicates that the window transmits low amount of solar heat. Solar heat gain coefficient mainly determines the type of glass that was used to make a window.

    A low-E glass has a protective coating that significantly reduces solar heat gain. This protective coating gives the glass desirable properties that help to control air conditioning during the summer. This does not mean that glasses with a higher SHGC are not desirable. Depending on the climate, a window with a higher SHGC can be suitable for your home. Other important considerations are the surrounding shade and the room’s orientation.

    Solar Heat Gain Coefficient
    Visible Transmittance

    Visible Transmittance (VT)

    This is yet another important measurement that is expressed as a percentage.

    Visible Transmittance refers to the amount of visible light that is allowed to pass through a given window material. What does that mean? A lower number is an indication that less light will enter the building. Low-E glass windows allow less light to enter as earlier discussed. A special coating is used to minimize solar heat gain. A comfortable balance can as well be achieved by high quality low-E windows. Highest quality low-E can let in enough natural light thus minimizing unnecessary heat gain.

    Air Leakage

    Air leakage is an important windows energy efficiency factor that cannot be overlooked. It refers to the amount of air passing through cracks in windows.

    A window that has a high air leakage rate is more prone to heat gain and loss. Such windows reduce interior comfort. You can as well say that such windows are not energy efficient. Improper installation of windows is one of the main causes of air leakage.

    Air Leakage


    You can always look at R-value in relation to U-value because they are reflections of a single process. However, there is a distinguishing feature between the two.

    R-value is the ability of a window to retain heat while U-value is the rate at which heat is lost through a window.

    Energy Rating (ER)

    When buying windows, this figure will help you to determine whether the material used is suitable for your house or not. This measurement gives the energy-efficiency score of windows. This figure encompasses SHGC, air leakage, and U-factor.

    Now that you have read and understood all these measurements, it will be quite easy to determine whether a give ER of a window will meet your needs or not. The figure gives you a simple and more accurate way of comparing different products. Different climate zones have different energy ratings.

    In Canada, for a window to earn an ENERGY START label, its minimum energy rating in zone 1 should be 25, 29 in zone 2 and 34 in zone 3.

    Energy Rating

    Benefits of Window Mart Windows

    Vinyl Windows have dominated the window market for its unique blend of style, high-performance and convenience. High-quality and energy-efficient vinyl windows deliver great return of investment through energy saving and by being a low maintenance product.

    100% Lead-free uPVC
    Window Mart Windows are made from a 100% lead-free uPVC powder compound. Their unique construction gives them excellent resistance to impact, cracking, and discoloration.

    Sealed Glass Unit
    Window Mart windows feature a completely sealed glass unit with 13/16″ overall thickness. We offer multiple options for glazing and thickness depending on the model.

    Fusion Welded Corners
    Fusion welding creates a watertight and airtight window frame. Internal walls are also welded to improve overall strength and structural integrity.

    Multiple Air Chambers
    Our windows have the highest number of internal air chambers, giving them outstanding insulation and sound abatement properties, as well as maximizing thermal & energy efficiency.

    Energy Efficient Windows

    Energy Efficient

    The unique multi-chamber design gives Window Mart windows the leading edge when it comes to energy efficiency.

    Low Maintenance Windows


    Spend less time on up-keep and more time doing the things you love with Window Mart’s low maintenance vinyl windows.

    Attractive Windows


    Give your home an instant facelift with stylish new vinyl windows available in a wide variety of shapes, styles, and sizes.

    Durable Windows


    Vinyl windows are exceptionally durable, boasting enhanced resistance to weather, cracking, and impact damage.

    Affordable Windows


    With a wide selection of price points and financing options, you are sure to find something that fits your style and your budget.

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    About Window Mart

    Window Mart pays close attention to great thermal performance of vinyl windows. Warm-edge spacers and low-E glass are used to improve the energy efficiency of vinyl windows.

    Do not compromise on professional installation because it is one of the main factors determining the Return on Investment and performance of vinyl windows. Window Mart will offer you the best services when it comes to window energy efficiency.

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