Energy efficiency is gaining favor all over the country so many homeowners are turning to home improvement projects to take advantage of the many energy efficient options available today. There are different ways to achieve energy efficiency but one of the easiest is to replace old, faulty windows with newer, more energy-efficient models available today.

What makes a window energy-efficient in the first place?

To understand what makes energy-efficient windows tick, you have to be aware of the factors that determine how well they perform. These include:

U-VALUE/U-FACTOR

The U-value or U-factor determines how much heat can flow through a window, including those passing through the glass pane, frame, seal and spacers. Measurements range from from 0 to 1, with the most energy-efficient windows having the lowest ratings. The lower a window’s U-value, the easier it will be for it to help a a home to stay cool during summer and warm during winter because outdoor heat is kept out and indoor heat stays in.

SOLAR HEAT GAIN COEFFICIENT

The Solar Heat Gain Coefficient or SHGC specifically measures how capable a window is in reducing the amount of heat it lets through from the sun, making it a crucial factor when choosing windows for areas with hotter climates. Like the U-value/U-factor, the SHGC scales from 0 to 1. The lower the score, the less heat a window lets through, making it the more energy-efficient option.

PART 1: HOW ENERGY-EFFICIENT IS ENERGY-EFFICIENT?

VISIBLE TRANSMITTANCE

Visible Transmittance or VT indicates the amount of light that passes through a window. A high VT rating is great for daylighting but keep in mind that sunlight brings both natural light and heat. Like the two other factors, VT scales from 0 to 1, with a higher score offering more natural light. The typical double-glazed window though can have VT scores ranging from 0.7 to 0.8. Adding tinted or reflective coatings can reduce values to as low as 0.1.

AIR LEAKAGE

A huge part of a window’s energy efficiency comes from its ability to stay airtight. This is where the Air Leakage rating comes in. Also scaled from 0 to 1, a rating must be as low as possible to be considered energy-efficient, with scores 0.3 and below being most ideal.

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To get good ratings, energy-efficient windows rely on certain features. In Part 2, we’ll be talking about glazing, one of these features. Read on for more!

PART 1: HOW ENERGY-EFFICIENT IS ENERGY-EFFICIENT?

The glazing or glass is a window’s biggest component, making up most of its sash. Given the area that it covers, glazing plays a major role in how energy-efficient a window can be. Thanks to technological innovations, new glazing options are now available, expanding choices to help homeowners find the best one for them.

SINGLE GLAZING

Single glazing is the simplest glazing option available to homeowners. Made up of just one layer of glass, it is available as either clear or tinted, both of which offer benefits depending on what you’re looking for. Most older windows use single glazing.

DOUBLE GLAZING

Double glazing or double-paned glass is now the standard in window replacements, and for good reason. With two layers of glass, double glazing can better prevent heat from passing through a window compared to single glazing, complemented by a layer of air or inert glass in between panes that further stunts heat transfer. Double glazing can also be coated, further improving function to lessen solar heat entering a home and preventing fading due to UV exposure. Tinted options can also provide better heat reflection, making them ideal in areas of your home that receive direct sunlight.

PART 2: WINDOW GLAZING AND ENERGY EFFICIENCY

TRIPLE GLAZING

Triple glazing is usually found in higher-end window replacements, featuring three individual panes of glass, as its name says. The addition of an extra glass pane adds another layer of protection against heat transfer, ensuring that outdoor heat stays out and indoor heat stays in, but this also means higher cost. Long-term savings from improved energy efficiency may make triple glazing a worthy investment but many find that, after comparing initial cost and benefits down the line, double-glazed windows may offer better overall value compared to their triple-glazed counterparts. Unlike single and double glazing though, triple glazing rarely has a tinted variant but can still feature low-emissivity coating.

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Now that you know about glazing, we’ll be moving on to other features windows have that can promote energy efficiency. Read on to learn more!

PART 2: WINDOW GLAZING AND ENERGY EFFICIENCY

While the glazing is largely responsible for how energy efficient a window could be, it is not the only component in a window that can help you improve energy efficiency in your home. Other window parts that can contribute include:

FRAMES

Windows today can use different kinds of frame materials, each one offering varying abilities to impart energy efficiency. Your best bet is to look for a material with the highest level of insulative properties. Wood is a great option but it requires a lot of maintenance, so it is not a practical choice for many homeowners. Vinyl offers respectable insulation and is easy to maintain. Composite, on the other hand, is more durable and performs better than vinyl but is just as easy to maintain and can be made to look like wood.

FOAM INSULATION

Foam insulation is found inside frames, tasked with further inhibiting the transfer of heat from one side of the frame to the other. A frame’s material on its own can keep heat from going through a window and foam insulation complements this function to offer better thermal performance. Foam is lightweight though so it will not hamper window installation or operation.

PART 3: OTHER ENERGY-EFFICIENT FEATURES FOR WINDOWS

SPECIAL COATINGS AND FILMS

These two are similar in that they improve window function when added to glazing. Depending on the coating or film used, it’s possible to boost thermal performance for a window, reduce the amount of heat being let in by a window or maximize visible transmittance. Low-emissivity coating, for instance, can drastically reduce heat that comes in through a window alongside sunlight without affecting the level of natural light being let in. Tinted films, on the other hand, can also significantly cut back on heat that enters a home but can block up to 90% of natural light as well, depending on the tinted film used, which may affect daylighting efforts.

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Interested in what these window features can do for you and your home? Don’t hesitate to get in touch with your local contractor to get you started. The sooner you find the right window for you, the sooner you can take advantage of improved energy efficiency in your home.

PART 3: OTHER ENERGY-EFFICIENT FEATURES FOR WINDOWS

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