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What Is an Insulated Glass Unit?
An insulated glass unit, commonly called an IGU, is a sealed glass assembly made with two or more panes separated by a spacer. The space between the panes contains air or an insulating gas, creating a barrier that reduces heat transfer through the glass.
IGUs are widely used in commercial windows, storefronts, exterior doors and residential window systems. They provide better thermal performance than a single pane while allowing natural light into the building.
Daltex Glass manufactures insulated glass units in-house for commercial and residential applications across Dallas-Fort Worth. Each unit can be produced to suit the required dimensions, glass type and project specifications.
What Does an Insulated Glass Unit Contain?
An IGU may look like a single piece of glass after installation, but it contains several components that work together.
Two or More Glass Panes
Most insulated glass units use two panes, which is why they are often described as double-pane or double-glazed glass. Some applications use three panes to create two insulating cavities.
The glass can be clear, tinted, reflective, tempered or laminated, depending on the application. Glass type and thickness must be selected according to the size, location, safety requirements and intended performance of the opening.
A Spacer
The spacer separates the panes and maintains a consistent distance between them. It runs around the perimeter of the unit and helps create the sealed cavity.
Spacer systems may contain a desiccant that absorbs small amounts of moisture remaining inside the unit during production. This helps prevent condensation from forming inside the sealed cavity when the unit is manufactured correctly.
A Sealed Airspace
The space between the panes forms the insulating part of the unit. It may contain dry air or a gas such as argon.
According to the U.S. Department of Energy, argon is commonly used because it reduces heat transfer and performs effectively within the typical space between panes. The exact cavity width and gas option should be chosen as part of the complete glass specification.
Perimeter Seals
The edges of an insulated glass unit are sealed to restrict the movement of air, moisture and insulating gas through the perimeter. The seal must remain intact throughout fabrication, transport, installation and use.
If the perimeter seal fails, moisture can enter the cavity and cause fogging or a cloudy appearance between the panes.
Optional Low-E Coating
Low-emissivity glass, usually called Low-E glass, has a thin coating designed to control radiant heat transfer. The coating can improve thermal performance while still allowing visible light through the window.
Different Low-E coatings are designed for different levels of solar heat gain and visible light transmission. This means the correct coating depends on the building, window orientation and performance requirements. The Department of Energy explains that Low-E coatings can reduce energy loss through windows, but the performance of a specific project depends on the entire window system rather than the glass coating alone.
How Is an Insulated Glass Unit Manufactured?
Manufacturing begins with confirmed dimensions and a complete glass specification. The glass panes are cut to size, processed as required and cleaned before assembly.
The spacer is prepared and positioned between the panes. The glass and spacer are assembled to form a consistent cavity, and the perimeter is sealed. When the specification calls for an insulating gas, the cavity is filled during the production process.
The completed unit is inspected before it is prepared for collection, delivery or installation. Accurate measurements are essential because a completed IGU cannot be trimmed on the jobsite to fit an incorrect opening.
Daltex provides glass supply and fabrication for contractors, glazing companies, property managers and project teams. Units can be produced according to a confirmed cut list, drawing or measured opening.
What Are the Benefits of Insulated Glass?
The main purpose of an IGU is to improve the thermal performance of a glazed opening. The sealed space between the panes slows the movement of heat through the glass.
Improved Thermal Performance
A single pane provides little resistance to heat transfer. Adding a second pane and a sealed cavity creates an insulating layer between the indoor and outdoor environments.
The resulting performance depends on several factors, including the number of panes, cavity width, spacer, gas fill, glass thickness and Low-E coating.
Better Indoor Comfort
The interior surface of an appropriate insulated glass system can remain closer to the indoor temperature than single-pane glass. This may help reduce uncomfortable temperature differences near windows.
Comfort still depends on the complete window assembly. The glass unit, frame, seals and installation must work together.
Solar-Heat Control
In the Dallas-Fort Worth climate, controlling solar heat can be an important part of the window specification. Low-E coatings, tinted glass and reflective glass can be used to manage how much solar energy passes through an opening.
Solar Heat Gain Coefficient, or SHGC, measures the amount of solar heat transmitted through a window system. A lower SHGC indicates that less solar heat passes through it. The appropriate value depends on the building design, window orientation and applicable project requirements.
Reduced Exterior Noise
An insulated glass unit may reduce some outside noise compared with a basic single pane. However, thermal insulation and acoustic performance are different requirements.
Projects with specific sound-control targets may require laminated glass, panes of different thicknesses or a specially designed cavity. An acoustic requirement should therefore be included in the glass specification from the beginning.
Where Are IGUs Used?
Insulated glass units are suitable for many commercial and residential openings, including:
- Commercial windows.
- Aluminum storefront systems.
- Curtain walls and window walls.
- Exterior glass doors.
- Office buildings.
- Retail and restaurant façades.
- Multifamily properties.
- Residential windows.
- Replacement units for fogged double-pane glass.
Daltex supplies and installs commercial windows and exterior doors that may incorporate insulated glass according to the project requirements.
For retail entrances and ground-floor façades, IGUs may also be used within commercial storefront systems when thermal performance is part of the specification.
What Is the Difference Between an IGU and Double-Pane Glass?
The terms are often used interchangeably, but they do not always mean exactly the same thing.
Double-pane glass describes an assembly containing two panes. An insulated glass unit describes the completed sealed assembly, including the panes, spacer, cavity and perimeter seals.
Most double-pane windows contain an IGU. However, the number of panes alone does not explain the complete performance of the window. Two units can both contain two panes but have different coatings, spacers, cavity widths and gas fills.
What Causes an Insulated Glass Unit to Fog?
Fogging between the panes usually indicates that the perimeter seal has failed and moisture has entered the cavity. Because the moisture is trapped inside the sealed unit, it cannot be cleaned from the room or exterior side.
A failed IGU may appear cloudy, hazy or wet between the panes. The appearance may change with outdoor temperature and humidity.
The practical solution is normally to replace the sealed glass unit. If the existing frame remains suitable, the IGU can often be replaced without replacing the entire window. Daltex offers glass repair and replacement for fogged, damaged and failed glass units.
Can an IGU Be Made to a Custom Size?
Yes. Insulated glass units can be manufactured to custom dimensions when the required glass, spacer and production specifications are confirmed.
Custom production is useful for commercial buildings, older properties and replacement projects where standard sizes may not match the existing frame. The opening must be measured carefully, including the width, height and available glazing-pocket depth.
Additional details may include:
- Overall unit thickness.
- Individual pane thickness.
- Glass type.
- Low-E coating.
- Tint or reflective finish.
- Spacer type and colour.
- Gas fill.
- Safety-glazing requirements.
- Edge and corner specifications.
All information should be confirmed before fabrication begins.
How Do You Choose the Right Insulated Glass Unit?
Start with the application rather than choosing a unit based only on price or appearance.
A project team should consider whether the IGU will be installed in a storefront, exterior door, curtain wall, commercial window or residential frame. The opening size, building orientation, safety requirements, desired thermal performance and existing frame will affect the specification.
For commercial work, drawings and glass schedules provide the clearest basis for pricing and production. For a replacement unit, photographs and initial dimensions can help begin the conversation, but final fabrication should use confirmed measurements.
Frequently Asked Questions
Is an insulated glass unit the same as a window?
No. The IGU is the sealed glass component installed inside a window sash or frame. A complete window also includes the frame, seals, hardware and installation system.
Are all insulated glass units filled with argon?
No. Some units contain dry air, while others use argon or another specified gas. The selected option depends on the required performance and complete unit design.
Can insulated glass be tempered?
One or more panes within an IGU can be tempered when safety glazing or additional strength is required. All cutting, drilling and edge processing must be completed before tempering.
Does Low-E glass make an IGU energy efficient?
Low-E coatings can improve performance by controlling radiant heat transfer. However, the performance of the finished window also depends on the spacer, cavity, gas fill, frame and installation.
Can a fogged IGU be resealed?
Once moisture appears between the panes, the durable solution is usually to replace the sealed unit. Surface cleaning cannot remove condensation trapped inside the cavity.
Can the glass unit be replaced without changing the frame?
Often, yes. If the frame is in suitable condition and can accept the required unit thickness, the old IGU may be removed and replaced. The frame and glazing pocket should be inspected before the new unit is ordered.
Insulated Glass Manufacturing in Dallas-Fort Worth
An insulated glass unit is more than two panes placed together. Its performance depends on the glass, spacer, cavity, coating, perimeter seal and the quality of the final installation.
Daltex Glass manufactures insulated glass units in-house and supplies glass for commercial and residential projects across Dallas-Fort Worth. Contractors, developers, property managers and homeowners can provide drawings, glass schedules or opening information to begin the quotation process.
To discuss an insulated glass unit for a new construction or replacement project, call 214-865-9961, email Or****@*********ss.com, or request a glass quote.
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