Why insulated glass units (IGUs) are key to a building’s performance

Applications and benefits of IGUs

IGUs are commonplace in both residential and commercial building envelopes. Residential applications tend to involve less window coverage, although this is starting to shift with larger IGUs becoming increasingly fashionable. Meanwhile, many commercial buildings use windows for structural purposes, thus occupying a greater proportion of the envelope and carrying more responsibility for the insulation performance of the building.

It should be noted that IGUs are also utilized in vehicles and transport applications, especially in public transport such as buses and trains which have large window coverage.  In a building and construction setting, however, there are numerous advantages to installing IGUs as part of the building envelope. These include:

• Fulfilling increasing insulation requirements
• Energy efficiency and financial gains through reductions in heat loss (i.e. a reduced need to use heating systems)
• Improved thermal comfort for building occupants
• Sound insulation that leads to increased comfort for building occupants, especially if the building is in a busy traffic district or industrial site

What components make up an IGU?

In order to deliver these multidimensional benefits, insulated glass units are far more engineered than simply placing two or three panes of glass a certain distance apart from each other.

There are many components that each have a key role to play:

Glass: The most obvious component, there are many specifications that can be used.

Spacer: Separates the glass and acts as a crucial barrier which retains the gas mixture within the IGU and keeps the moisture out. The spacer also houses desiccant, with warm edge spacers using a barrier film – these are critical components supplied by Avery Dennison Performance Tapes.

Desiccant: Small granules which act as a drying agent by absorbing moisture from the hermetically sealed space.

Gas: The gas mixture contained within the IGU is usually dry air or inert gas such as argon, krypton or xenon. This helps reduce the overall heat transfer coefficient, known as the U-value.

Primary sealant: Typically made from PolyIsoButylene (PIB) or acrylate PSA, the role of the primary sealant is to hold the spacer in place during the assembly process (i.e. until the secondary sealant takes hold)

Secondary sealant: The secondary sealant is commonly made out of silicone, PU, polysulfide or butyl, and takes over from the primary sealant once in place. It structurally holds the unit together and is designed to be long-term weather resistant.

There are, of course, many different types of the above components that perform the same functions, albeit to varying degrees of effectiveness. For example, warm edge spacers have emerged as superior alternatives to traditional metal (or cold edge) spacers for a number of reasons – this is the subject of another case study which you can read here