Cavity Wall Changes Part L 2021

by | May 2, 2024 | Last Articles | 0 comments

Navigating Traditional Cavity Construction Changes: Understanding the Viability of 100mm Cavities

In anticipation of the forthcoming Part L Regulations update in June 2022, the question arises: Are 100mm cavities still permissible? The answer is affirmative, but the path forward may pose increasing challenges.

As the regulatory landscape evolves, meeting the standards set by SAP Calculations with a 100mm cavity is currently feasible, albeit with difficulty. However, the impending adjustment to Part L introduces a stricter benchmark—a notional U-Value of 0.18 W/m²K. Presently, an average U-Value achieved with a 100mm cavity and materials like Dritherm 32 hovers around 0.25 W/m²K.

While the maximum allowable U-Value for walls remains at 0.25 W/m²K, surpassing the notional value necessitates compensatory measures elsewhere. With standards tightening, achieving this will prove increasingly arduous, likely prompting a shift towards 125/150mm cavities as the new norm.

Alternatively, opting for high-performance PIR insulation, such as Celotex or Kingspan, presents a viable solution – with partial filling cavity walls. These materials offer superior U-Values, enabling compliance with narrower cavities compared to traditional roll or batt insulations.

To clarify, the utilization of 100mm cavities isn’t outright prohibited. However, meeting the requisite U-Values for external walls mandates either wider cavities or adoption of more efficient insulation options. This underscores the imperative for adaptation and innovation in construction practices.

For more information or to discuss your specific project requirements, please Contact Us.