EN 1279 Glass in Buildings - Insulated Glass Units

The European standard “EN 1279 Glass in buildings - Insulated glass units” consists of the following sub-sections published under the same title:

The EN 1279-1 Part 1: General information, system description, substitution rules, tolerances and visual quality standard describes the requirements for insulated glass units. The main applications of insulated glass units are installations in windows, doors, curtain walls, bonded glazing systems for doors, windows and curtain walls, roofs and partition walls.

Meeting the requirements of this standard demonstrates that the insulated glass units are fit for their intended use and, through assessment of compliance with this standard, guarantees that the visual, energy, acoustic, and safety parameters have not changed significantly over time.

In cases where there is no direct protection against ultraviolet radiation or continuous shear load at the edge seal, for example in bonded glazing systems for doors, windows and curtain walls, compliance with EN 15434, EN 13022 1 and EN 16759 standards is also required.

Insulated glass units designed for artistic purposes (e.g., leaded glass or fused glass) are outside the scope of this standard. Vacuum insulated glass is also not covered. Glass/plastic composites are included, provided the surface in contact with the sealing material is a glass component.

For glass products with electrical wiring or connections for purposes such as alarm or heating, other directives apply, such as the low voltage directive.

Insulated glass units consist of two or more glass panels separated by an airtight air gap filled with air or inert gases such as argon or krypton. The edges are sealed to prevent moisture ingress and gas leakage, thereby improving thermal insulation, sound insulation, and energy efficiency in buildings. These units are indispensable for modern construction and help reduce heating and cooling costs while increasing the comfort of building occupants.

This standard provides the general framework for insulated glass units, including:

Definitions and terminology for components such as glass panels, spacers, sealants, desiccants, and gap fillers.
System disclosure guidelines: Manufacturers must describe their insulated glass unit systems (specific combination of materials and designs) in detail to ensure consistency and traceability.
Replacement guidelines: Guidelines on when and how components (e.g., sealants or desiccants) can be replaced without retesting the entire system, provided performance remains equivalent.
Dimensional tolerances: Specifications for allowed variations in size, thickness, and shape (including curved units with bending radii).
Optical and visual quality requirements: Defects, clarity, and appearance criteria to ensure units meet aesthetic and functional standards.

This approach, prioritizing durability, ensures that insulated glass units maintain their performance over time without significant changes in heat transfer, solar factor, sound insulation, or mechanical strength.

The standard “EN 1279-2 Part 2: Long-term test method and requirements for moisture penetration” describes the test method for determining the moisture permeability index and the requirements for limit values for insulating glass units in the following cases:
Insulating glass units manufactured in accordance with EN 1279-1 standard and produced according to EN 1279-6 standard.
Insulating glass units manufactured to demonstrate that the components (e.g., edge seals or spacers) ensure compliance with the requirements of the EN 1279-1 standard for the insulating glass unit.

Insulated glass units rely on a hermetically sealed cavity to maintain low heat transfer. The desiccants inside the spacer absorb the initial and small amount of moisture, but if the edge seal fails, external moisture penetrates inward, saturating the desiccant and causing:

Condensation or fogging on the interior.
Loss of insulation properties.
Reduced sound insulation and visibility.
Potential safety issues arising from changes in mechanical strength.

The EN 1279-2 standard promotes energy efficiency and sustainability in buildings by ensuring long-term durability. This standard specifies limit values for the moisture permeability index. After testing, the units should demonstrate the following:

Low thermal conductivity or no significant change in solar factor (maintaining energy performance).
No deterioration affecting health (e.g., sound insulation, clear vision).
Maintaining mechanical resistance for safety.

This standard defines precise limits (e.g., maximum permissible index values), ensuring the suitability of the insulated glass unit throughout its expected service life.

The standard “EN 1279-3 Part 3: Long-term test method and requirements for gas leakage rate and gas concentration tolerances” describes the test method for determining the gas leakage rate and the requirements for limit values for gas leakage rate and gas concentration for gas-filled insulating glass units in the following cases:
Insulating glass units manufactured in accordance with EN 1279-1 standard and produced according to EN 1279-6 standard.
Insulating glass units manufactured to demonstrate that the components (e.g., edge seals or spacers) ensure compliance with the requirements given in the EN 1279-1 standard.

Many modern insulated glass units are filled with inert gases such as argon, krypton, or xenon instead of air. These gases have lower thermal conductivity, significantly increasing the unit's heat transfer rating and overall energy efficiency. However, if a leak occurs at the edge seal, the gas will escape over time, reducing insulation performance, increasing energy costs, and potentially leading to premature failure. This standard ensures that gas-filled insulated glass units maintain their declared thermal properties throughout their service life.

Compliance with the EN 1279-3 standard is crucial for system certification and type testing. It verifies edge sealing quality and allows substitution under the EN 1279-1 standard. For specifiers and builders, it guarantees sustainable energy savings and a reduced carbon footprint in buildings.

While gas chromatography remains the reference method, non-invasive instruments (e.g., spark emission spectroscopy) are increasingly being used for manufacturing quality control and may be compliant with the standard's accuracy requirements. This standard is essential for maximizing the benefits of gas-filled glass in sustainable, high-performance architecture.

The standard “EN 1279-4 Part 4: Test methods for the physical properties of edge sealing components and fittings” describes the requirements and test methods for edge sealing components and fittings. This includes identification, determination of physical properties, and evaluation of properties for use in substitution rules in accordance with the EN 1279-1 standard. It also applies to EN 1279-2 and EN 1279-3 standards to demonstrate that the edge sealing components ensure compliance with the requirements given in EN 1279-1 for the insulating glass unit.

Edge sealing is the most critical component of insulated glass units, providing structural integrity, adhesion to the glass, and resistance to environmental stresses. Poor seals can lead to layer separation, loss of gas filling, moisture ingress, or complete failure. This standard allows manufacturers to qualify new materials (e.g., alternative sealing materials or hot edge spacers) without retesting entire units, by testing components individually, thus facilitating innovation while maintaining performance.

The EN 1279-4 standard supports efficient type testing and material innovation, ensuring that edge seals contribute to long-lasting and energy-efficient glass. It is particularly valuable for validating modern materials such as flexible spacers or advanced sealing materials that enhance thermal performance. This standard supports the reliability of edge seals, a cornerstone of high-performance insulating glass in sustainable building design.

The standard “EN 1279-5 Part 5: Product standard” covers the product standard for insulated glass units designed for use in buildings. Units designed solely for artistic purposes and therefore not requiring essential specifications are not subject to CE marking and are not covered by this standard. For example, for glass products with electrical wiring or connections for alarm or heating purposes, other directives may apply, such as the low-voltage directive.

Consistent compliance ensures that insulated glass units deliver the declared energy efficiency, safety, and longevity in real-world installations. It protects consumers, supports building regulations (e.g., energy performance directives), and enables fair market competition. Lack of compliance can lead to product recalls, fines, or liability due to failures such as seal failure.

Manufacturers must implement robust systems, typically verified by third-party organizations, to issue performance declarations and add markings. This standard facilitates innovation by allowing verified substitutions while maintaining traceability and reliability. This standard ensures that insulating glass units reliably contribute to sustainable, high-performance buildings across Europe.

The standard “EN 1279-6 Part 6: Factory production control and periodic testing” describes routine factory production control, periodic testing and inspection, and test methods for verifying the conformity of insulated glass units to the system definition.

Consistent production is vital because even small variations can jeopardize long-term durability by leading to condensation, gas loss, or reduced energy performance. This standard protects building owners from premature failures and supports Europe's energy efficiency targets by ensuring that high standards proven in laboratory-type tests are maintained in real-world production.

Implementing this standard typically involves third-party audits conducted by authorized bodies, which enhances confidence and ensures market access. It also fosters innovation by allowing controlled changes within the system while maintaining quality. This standard guarantees that insulated glass units provide reliable and consistent performance in sustainable architecture.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services to businesses in accordance with the "EN 1279 Glass in Buildings - Insulated Glass Units" standard.