INSIGHT
Thermal Bridging: Bridging The Performance Gap
In this article, we examine the impact of updated UK Building Regulations on thermal bridging calculations and the necessity of bespoke Psi values for more accurate results.
Understanding Thermal Bridging
Thermal bridging occurs when heat flows through a building's materials more easily at certain points, like the joints between walls and floors, leading to energy loss and reduced insulation effectiveness.
Performance Insight:
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Up to 30% of heat loss can be attributed to poor thermal bridging
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Enhanced thermal bridging detail can improve EPC rating by an entire band (from B to A)
Overview
Up to 30% of a dwelling's heat loss can be attributed to poor thermal bridging, also called a cold bridge, thermal bypass, or heat bridge. This is where weak points (or areas) in the envelope of a building allow heat to pass through, such as a gap in the insulation or an object which has higher thermal conductivity versus other surrounding materials. Updated UK Building Regulations (Part L, 2021) require SAP assessors to use more advanced Psi methods to calculate thermal bridging. In this article, we discuss how these values affect SAP and EPC performance and the key requirements to meet energy efficiency targets.
New Building Regulations
The recent update to Building Regulations (Part L, 2021) has removed the previously accepted Accredited Construction Details (ACDs) for thermal bridge junctions. As a result, SAP assessors must now rely on either default Psi values or project-specific bespoke calculations. This change is crucial for non-standard construction methods, such as timber or steel frames, where enhanced details are limited.
The Importance of Bespoke Thermal Bridging Calculations
With ACDs no longer permitted, Psi values for junction details must come from other reference libraries or be calculated specifically for each project. While default values can still be used, achieving the required compliance metrics is significantly more difficult without bespoke Psi values. At Viro, we can calculate bespoke Psi values, which is crucial in forming a better and more accurate view of energy performance.
Impact on SAP and EPC Performance
Enhanced details can substantially improve the Dwelling Emissions Rate (DER) and Dwelling Primary Energy Use (DPER), often pushing a dwelling over the compliance threshold. This improvement can reduce the need for additional measures, such as solar PV systems or wastewater heat recovery (WWHR) systems.
Specific Challenges and Opportunities in England
New builds in England must meet the Dwelling Fabric Energy Efficiency (DFEE) targets. These targets can only be achieved through fabric improvements, making them nearly impossible to meet without calculated Psi values. If default Psi values were used in an English new build assessment, achieving DFEE targets would be extremely challenging, necessitating near Passivhaus standards for the rest of the building. This demonstrates the benefit of using specific calculations for more accurate Psi values, versus relying on default values and potentially misleading calculations.
Viro's Role in Navigating New Regulations and Achieving Compliance
Bespoke calculated Psi values from Viro ensure that projects in England meet these stricter targets without excessive measures in other areas. Viro's expertise helps optimise energy performance and achieve compliance in line with updated regulations.
Further Thermal Bridging Considerations
By understanding and utilising bespoke Psi values, construction projects can better manage thermal bridging, resulting in more energy-efficient and environmentally friendly buildings. This proactive approach not only meets regulatory requirements but also aligns with broader sustainability goals, contributing to a greener future. Viro's commitment to providing precise, project-specific thermal bridging calculations ensures that clients can confidently meet the updated building standards, ultimately enhancing the value and performance of their developments.
