Salem's 2025 Guide to Insulated Glass Units
What is an Insulated Glass Unit (IGU) in Windows?
An Insulated Glass Unit (IGU), also known as a double-glazed window or triple-glazed window, is a multi-layered glass panel designed to improve energy efficiency by reducing heat transfer between the inside and outside of a building. Typically used in residential and commercial windows, IGUs are composed of two or more lites/panes of glass separated by an air or gas-filled spacer. The layers work together to insulate against heat, cold, and noise, making them an essential component in energy-efficient window systems.
How are Insulated Glass Units Made?
Creating an Insulated Glass Unit involves assembling two or more glass lites with a spacer in between, which is sealed to form a single unit. This process includes:
- Lite Selection: Choosing the right type of glass (clear, tinted, low-E, or reflective) based on performance needs.
- Spacer Placement: A spacer, often filled with a desiccant to prevent moisture, is inserted between the glass layers. This spacer creates an insulating gap.
- Sealing the Unit: The unit is then sealed along the edges with high-quality sealants, ensuring air or gas (like argon or krypton) remains trapped between the lites.
- Gas Filling: For added insulation, an inert gas such as argon is often injected into the space between the lites to further reduce heat transfer.
How Do They Make Insulated Glass Units?
Manufacturers use precision machinery to assemble insulated glass units (IGUs), ensuring a consistent gap between the lites and achieving an airtight seal.. The sealed edges prevent condensation and keep the unit energy efficient. IGUs are tested for durability and thermal performance to meet high industry standards. This complex production process ensures that each unit provides optimal insulation and contributes to overall energy efficiency.
Is Thicker Glass a Better Insulator?
While thicker glass can slightly improve insulation, it is not necessarily the main factor in a window's insulating performance. The air or gas-filled space between the lites in an IGU is far more important for thermal efficiency. Adding low-emissivity (low-E) coatings or using gas fills like argon improves the insulation even further. In general, an IGU with multiple layers, gas fills, and low-E coatings provides significantly better insulation than a single thick lite of glass.
What is the Difference Between IGU and DGU?
An IGU (insulated glass unit) and DGU (double glazed unit) refer to similar products, with DGU being a type of IGU. A DGU has two lites of glass with an insulating gap in between, making it a common type of IGU. However, IGU is a broader term that can refer to any multi-lite insulated glass unit, whether it’s double-glazed (two lites) or triple-glazed (three lites). Both IGUs and DGUs enhance thermal insulation, but triple-glazed IGUs offer even greater energy efficiency and sound insulation than DGUs.
How Much Does an Insulated Glass Unit Cost?
The cost of an insulated glass unit (IGU) can vary widely depending on factors like the number of lites, type of glass, coatings, and gas fills. On average, a basic double-glazed IGU may cost between $10 to $20 per square foot and cost an additional $150 to $600 in labor to replace. Advanced selections like Low-E glass, triple-glazed and insulated-laminated units will also affect pricing. Costs may also vary based on shape and additional customization options, but the investment in IGUs typically pays off in long-term energy savings and comfort.