EN 678 Determination of Dry Density of Autoclaved Aerated Concrete

The European standard “EN 678 Determination of dry density of autoclaved aerated concrete” describes a procedure for determining the dry density of prismatic samples of autoclaved aerated concrete.

In principle, test samples are taken from pre-produced components. Dry density is determined as the ratio of the mass to the volume of the test samples after they have been dried to a constant mass at 105 degrees plus/minus 5 degrees.

The EN 678 standard defines a method for determining the linear heat transfer of window and door frame profiles. It is primarily used in the building and construction industry to assess heat loss through frame components, particularly at junctions between different materials (e.g., glass, frame, and spacers).

This standard is closely related to thermal performance calculations for window systems and supports compliance with energy efficiency regulations across Europe.

The EN 678 standard provides a calculation-based approach (rather than purely experimental testing) for determining heat flow through window frame sections. It focuses on:

• Thermal bridging effects in frame and edge regions
• Linear heat transfer at the glass/frame interface.
• Supporting the accurate calculation of the overall U-value of windows and doors (the U-value of windows and doors, i.e., heat transmittance, is a measure of how much heat passes through them, indicating how well a window or door insulates).

This standard is often used in conjunction with the following standards:

• EN ISO 10077 (thermal performance of windows and doors)
• EN 673 (thermal transmittance of glass)

The linear heat transfer value represents the additional heat loss that occurs at junctions, such as where the glass meets the frame. Even if the materials perform well individually, these junctions can significantly affect the overall heat efficiency.

The EN 678 standard uses numerical simulation methods (e.g., finite element or finite difference methods) to model heat transfer through cross-sections of window frames (two-dimensional heat flow modeling). This allows for:

• Detailed thermal mapping
• Identifying weak points (thermal bridges)
• Optimization of frame design

This standard specifies internal and external temperature conditions, surface resistances, and material properties to ensure consistent and comparable results.

The general process under the EN 678 standard includes the following:

• Geometric definition: A cross-section of the window or door frame is created, including the glass and spacer components.
• Material properties input: Thermal conductivity values ​​are assigned to each material (e.g., aluminum, PVC, wood, glass).
• Numerical simulation: Heat transfer is calculated using validated software tools.
• Conclusion: The linear heat transfer value is obtained from the simulation results and is then used in subsequent thermal calculations.

The EN 678 standard is widely used in the following areas:

• Window and door manufacturing
• Facade engineering
• Building energy performance assessments
• Passive house and low-energy building design.

This standard also helps designers and engineers improve the following:

• Insulation performance
• Energy efficiency ratings
• Compliance with building regulations

Although the EN 678 standard is widely used, it has some limitations:

• It relies on accurate input data; incorrect material properties can lead to misleading results.
• It requires specialized simulation software and expertise.
• It focuses on two-dimensional heat flow, which may not capture all the real-world three-dimensional effects in complex systems.

The necessity of the EN 678 standard rests on one thing: correctly understanding and controlling heat loss through windows and doors, especially at the weakest points that are often overlooked. The main reasons why this standard is considered necessary are as follows:

• It captures latent heat loss (thermal bridges): Most heat loss in windows doesn't just pass through the glass; it also occurs at the junction between the glass and the frame. Without this standard,
  • These edge losses are often ignored or underestimated.
  • The total window performance (U-value, i.e., heat transfer) would be incorrect.

This standard specifically calculates linear thermal transmittance taking these edge effects into account.

• It enables accurate U-value (heat transfer) calculations: The overall thermal performance of a window depends on multiple components such as glass, frame, and edge losses. This standard ensures the accurate inclusion of edge contribution, making the final U-value realistic and reliable.
• It supports energy-efficient building design: Modern buildings must meet stringent energy targets. Small heat losses can significantly impact:
  • Heating and cooling demand
  • Energy certificates
  • Compliance with regulations

By using this standard, designers can:

• It can identify weak points.
• It can optimize frame and spacer design.
• It can reduce unnecessary energy loss.

• Fair product comparison
• Consistent engineering practices
• Reliable performance data

• It enables product innovation: Manufacturers use this standard for the following purposes:
  • Developing better spacers (e.g., thermally insulated spacers)
  • Improving the frame geometry
  • To improve insulation performance.

Without this standard, improvements would rely on trial and error rather than rigorous analysis.

In short, the EN 678 standard is essential because it fills a critical gap in thermal analysis by measuring heat loss at the glass-frame interface. This leads to more accurate energy calculations, better performing windows, and more efficient, durable buildings.

In conclusion, the EN 678 standard is crucial for evaluating the thermal performance of window and door frames, particularly at junctions where heat loss is often underestimated. By providing a structured and reliable calculation method, it supports energy-efficient building design, product innovation, and regulatory compliance across Europe.

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 in accordance with the EN 678 standard.