What are SIP & Timber Splines?

Structural Insulated Panels (SIPs) are a cornerstone of modern, energy-efficient construction, providing both insulation and structural strength in one integrated system. Within Formance SIPs, one of the critical components that ensures the panels function effectively is the type of spline used to join them. The two main types are timber splines and thermal splines. Each serves a distinct purpose, and choosing the right one can significantly impact both the structural and thermal performance of your building.

Timber Splines: Prioritizing Structural Support

Timber splines are designed for applications that require extra structural support. Typically constructed from timber, these splines are inserted into the edges of SIPs to reinforce the connection between panels. Each timber spline consists of two 45mm wide pieces, with varying depths ranging from 90mm up to 290mm, allowing for flexibility in different structural applications.

Key Characteristics of Timber Splines:

• Structural Integrity: Timber splines excel in providing the necessary strength for load-bearing applications, making them ideal for use in walls and roofs that are subject to significant forces.
• Versatility: The range of sizes ensures that you can select a spline that meets the specific load-bearing needs of your project.
• Installation Process: These splines are secured by nailing them into the panel rebates, followed by gluing and foaming to ensure a tight, secure join. This method not only strengthens the connection but also helps maintain an airtight seal.

However, one trade-off with timber splines is the issue of thermal bridging. Since wood is a better conductor of heat compared to the insulating core of the SIPs, using timber splines can slightly reduce the overall thermal efficiency of the panels.

Thermal Splines: Enhancing Energy Efficiency

In contrast, thermal splines are specifically engineered to maintain the thermal integrity of Formance SIPs. Made from the same Expanded Polystyrene (EPS) material as the core of the panels, or a similar insulating material, thermal splines minimize thermal bridging, making them crucial for projects where energy efficiency is a top priority. Like timber splines, each thermal spline consists of two 45mm wide pieces, but they are optimized for minimizing heat loss without compromising the structural connection.

At Formance, we strive to specify thermal splines wherever possible due to their clear advantages in maintaining the panel’s R-value and overall energy performance. By reducing thermal bridging, these splines help ensure that the building envelope remains as insulated and efficient as possible.

Key Characteristics of Thermal Splines:

• Thermal Efficiency: The main advantage of thermal splines is their ability to prevent heat loss through panel joints, thereby preserving the high R-value of the SIPs. This makes them particularly valuable in cold climates or energy-efficient building designs.
• Application: These splines are typically used in full-height wall panels and, in some cases, roof panels, where maintaining a consistent thermal barrier is essential.
• Installation: Like timber splines, thermal splines are installed using glue, foam, and nails. However, their insulating properties ensure that the panel's thermal performance remains uncompromised.

Making the Right Choice with the Formance Design Guide

Selecting the appropriate spline type is crucial and should be guided by the specific needs of your project. For instance, if your design prioritizes structural strength, particularly in load-bearing walls or expansive roof spans, timber splines are the preferred choice. However, where possible, we always recommend thermal splines to maximize energy efficiency and maintain optimal thermal performance.

To make the best decision, it's important to consult the Formance Design Guide. This comprehensive resource will help you evaluate your project's requirements and determine the most suitable spline type, including the appropriate size, ensuring that your building achieves the desired balance of strength and energy efficiency.

Conclusion

Understanding the differences between timber and thermal splines allows for informed decisions that optimize the performance of Formance SIPs in your building project. While timber splines offer superior structural support, thermal splines are essential for maximizing energy efficiency. By using the Formance Design Guide to select the appropriate spline type and size, and prioritizing thermal splines where possible, you can ensure your building is both strong and energy-efficient.