What Is a Double Glazed Window?

What Is a Double Glazed Window?

Updated: 07.28.2023

By Nina Tsoy

Windows are an integral part of every building and vital for comfortable living. Good-looking windows are an essential design element and add to the pleasant general appearance of the house. Each window unit typically consists of glazed parts, frames, sealants, and fittings.

A window’s noise reduction and insulation abilities depend on the quality of every component. Compared to single-glazed windows, a double-paned window glass replacement is more popular due to its energy efficiency.

Let’s look deeper at what double-paned windows are made from and their benefits.

What Is Double Glazing?

what is double glazed windows

Double-glazed windows have two panes of glass with a gap between them. The gap is typically filled with a gas such as argon, krypton, or a combination of both, improving the window’s insulation and soundproofing.

It also creates a vacuum, further enhancing the insulation and eliminating thermal bridges. Double-glazing can also be combined with other treatments, such as low-emissivity and UV-resistant coatings, to improve energy efficiency.

We should mention here that the re-glazing services offered by Apex Window Werks only include changing glass pieces rather than replacing the entire unit. We provide only the necessary work needed, so you don’t incur extra costs unless necessary.

How Double Glazed Glass Windows Work

double glazed windows

Dual-glazed windows consist of the following:

  • Double-glazed unit or insulated glass unit (IGU)
  • Air space
  • Spacer
  • Wood, aluminum, or uPVC frame
  • Desiccant
  • Seal

As we mentioned above, double-glazed windows use a gas insulation layer, such as air, xenon, argon, or krypton, between two panes of glass to reduce the heat changes between the inside and outside of the house.

It is more difficult for heat to be conducted through two panes of glass and a gap of air. Therefore, double-glazed windows have a much higher insulation rate, resulting in improved thermal insulation for your home or building.

The glass in the window usually ranges from 4mm to 6mm thick, and the gas layer from 6mm to 20mm. The average double-pane window thickness is 24mm.

Installing thicker double-glazed or even triple-glazed windows can reduce noise and minimize heat loss; however, this comes at an increased price.

What Are the Benefits of Double Glazed Windows?

double glazed glass

Many homeowners choose cost-effective standard single-paned windows and doors.

However, dual-glazed glass has many more benefits:

  • Increased insulation: Double glazing’s insulation properties prevent airflow between the two panes, keeping the home cool in summer and warm in winter. This helps maintain a comfortable temperature without relying on artificial heating or cooling;
  • Lower energy bills: The insulation abilities of window double glazing keep the warm air in during the winter and the cool air in during the summer, meaning that air conditioning and central heating systems don’t have to work as hard to maintain a comfortable temperature in the building;
  • Improved security: These windows can withstand greater force than single panes. And they can be further fortified by laminating or reinforcing the glass;
  • Noise reduction: The World Health Organization has discovered that prolonged exposure to noise can lead to stress, sleep disturbances, cognitive issues, and even health problems like cardiovascular disease. Double-glazed products are significantly more soundproof than single-glazed products due to the gap between the glass panes. Installing acoustic glass on top of double glazing will further improve its sound insulation efficacy;
  • Less condensation: Condensation forms when moist air inside a home encounters a colder surface, like a single-glazed window. This eventually becomes a problem, but double-glazing products help avoid it. Keeping the interior pane of the window close to room temperature minimizes the risk of condensation.

Common Issues with Double Glazed Windows

When installing double-glazed windows, one must consider the whole unit, including the framing material, and how it affects energy efficiency.

For instance, aluminum window frames by themselves conduct heat and cold, although if they are constructively enhanced, they can help counteract the cost of installing double glazing.

Additionally, the dimension of airflow through the gap and the type of spacer used are essential variables to consider. If the double-glazed unit seals are incorrectly installed or the spacer lacks the proper amount of desiccant, it can reduce the performance.

Double Glazed Windows Pros and Cons
Double-Glazed Window BenefitsDouble-Glazed Window Disadvantages
Increased energy efficiency Higher installation costs
Noise reduction Limited ventilation
Improved security Heat gain
Lower condensation

Factors to Consider When Buying Double Glazed Windows

Like many building considerations, double-glazed windows aren’t a one-size fits all solution. You must also consider the types of double-pane window frames, gas, and glass.

And, if you need expert advice and expertise, Apex Window Werks is here to help with fitting double-glazed windows.

#1. Types of Frames

what are double pane windows

  • Aluminum Frames – durable, lightweight, low-maintenance, and cost-effective;
  • Vinyl Frames – energy-efficient, low-maintenance, and inexpensive to install;
  • Wood Frames – traditional look, easy to ornament, strong insulation;
  • Fiberglass Frames – durable, energy-efficient, long-lasting, low maintenance;
  • Steel Frames – strong, durable, low maintenance, inexpensive, and energy efficient.

#2 What’s in Between

  • Argon Gas – a great insulator with low thermal conductivity. Non-toxic, odorless, and relatively inexpensive, making it the most popular gas for double glazing;
  • Krypton Gas – slightly more expensive than Argon gas, but with better insulation properties;
  • Xenon Gas – has the highest thermal insulation capacity of all three gasses but is the most expensive;
  • Vacuum Pane – uses a vacuum between two panes to reduce heat transfer. It’s the most effective and the most expensive.

#3. Type of Glass

  • ​​Annealed or float glass – made by floating molten glass on top of molten tin. It is typically cooled slowly to relieve internal stresses, making it strong but impact-resistant;
  • Tempered or toughened glass – formed by heating the annealed glass to a high temperature before rapidly plunging it into the cool water, which makes the glass stronger than annealed glass and impact-resistant;
  • Laminated glass – Created by bonding two pieces of annealed glass with one or more layers of plastic. It is strong and protects against ultraviolet (UV) radiation and noise;
  • Low-emissivity (Low E) glass – Designed with a special coating that helps reduce heat transfer. It is often used to help conserve energy;
  • Self-cleaning glass – Coated with a unique material that reacts with the sun’s ultraviolet (UV) radiation to break down dirt and grime;
  • Noise reduction glass – Designed to reduce noise, often by having special layers to absorb sound waves;
  • Frosted glass – A special etching creates a cloudy or translucent effect that provides privacy while still allowing light to shine through.

Double Glazing Window Ratings

double paned window

The National Fenestration Rating Council (NFRC), a non-profit organization established in 1978, sets the standards for window energy ratings in the United States.

See the criteria below:

Energy Rating

The rating of a window is calculated using a formula that takes into consideration the total solar heat transmittance (generally known as g-value), the U-value (i.e., how well the window holds heat inside your home), and the amount of air infiltration (i.e., degree of the seal of the window).
A standard window size and setup are applied when evaluating to maintain standardization across all products. The rating value is then placed into a rating band – ranging from E to A++, with A++-rated windows being the most energy-efficient – consistent with other products with energy rating labels, like washing machines, light bulbs, and refrigerators.

The U Value

The U-value measures how well a material or construction structure conducts heat (in units of W/m2K). It measures heat loss in a window and indicates how well the window is insulated.
(Remember that the U-value measures heat transmission, while the energy rating is an overall assessment of the window’s energy efficiency.)
For instance, a single-glazed window typically has a U value of 5.88. In contrast, double glazing offers a much lower U value of 2.81, resulting in around a 50% reduction in thermal loss. Even better results can be achieved with specialist glazing options.

Solar Heat Gain Coefficient

Solar Heat Gain Coefficient (SHGC) measures a window’s ability to transmit solar radiation. It is the ratio of solar heat gain entering the window compared to the solar radiation hitting it. The lower the SHGC, the less solar heat is transmitted through the window.

Visible Transmittance

Visible transmittance measures the amount of visible light that passes through a material, usually a transparent or translucent material such as glass. It is calculated as a percentage of the total visible light incident on the transmitted material surface.

Window RatingU-FactorSolar Heat Gain Coefficient (SHGC)Visible Transmittance (VT)
Very High Efficiency0.25 or less0.30 or less0.70 or more
High Efficiency0.30 to 0.350.35 to 0.400.60 to 0.70
Moderate Efficiency0.35 to 0.400.40 to 0.450.50 to 0.60
Low Efficiency0.40 or more0.45 or more0.45 or less

The Cost of Double Pane Windows

The cost for two-pane glass can range from $385 to $900. Frame material is the main factor that affects the price; aluminum is the most cost-effective option, while wood is much pricier at almost $900 per window. It’s essential to do some comparison shopping and get multiple quotes to make the right decision. Check for deals based on the number of windows you are installing.

Tips for Improving Window Efficiency

what is double pane windows

No matter how great double pane windows’ benefits are, there are measures you can take to maximize their insulation and minimize energy loss.

Here are some tips to help optimize the efficiency of your windows:

  • Use thermal curtains – hang thick curtains across the windows at night to increase R-value;
  • Add insulation film – apply to windows to keep out cold air and reduce heat loss;
  • Weatherproofing – use exterior-grade silicone caulk to fill and seal the gaps;
  • Replace foggy windowsreplacing foggy windows improves insulation;
  • Install window awnings – window awnings reduce heat gain and glare.

One may think that it is convenient to call the nearest company. Still, considering our experience in this field, it is always better to address all glazing service requests to an experienced company.

Apex Window Werks technicians in IL, WI, MN, and OH states have deep knowledge in installing glazing constructions and, with the help of special equipment, easily cope with requests of different complexity.

Trust Experts with Your Double Glazed Window Installation Project!

The correct function of the double-glazed window depends on the quality of installation works. Call us today to discuss your double-glazing window options.

Contact Us

or call us (847)-443-5145

Nina Tsoy

Nina Tsoy

With over 15 years of experience in the window repair, replacement, and manufacturing business, Nina is in charge for strategic solutions and exceptional operational performance at Apex Window Werks. This allows her to offer innovative techniques and solutions to address any window-related problem, all while adhering to industry standards and best practices.

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