Marmox - Helping an Architect Improve SBEM Performance

From CPD to Project Support – Helping an Architect Improve SBEM Performance

Overview

A Thermal Bridging Continuing Professional Development (CPD) seminar delivered by Marmox led to an ongoing technical support for architectural practice Chaplin Farrant. Following the presentation, the practice sought Marmox's assistance in calculating project-specific Ψ-values for a live commercial project, enabling the design team to move away from conservative default values used within the SBEM assessment.

The Challenge

During the design of a commercial building, the project team identified that their SBEM assessment relied on default Ψ-values for several junctions.

While default values can be used where no evidence is available, they are intentionally conservative and can have a significant impact on the overall energy performance of a building. Higher Ψ-values increase heat loss through junctions, often forcing designers to compensate with lower U-values elsewhere in the building fabric or through additional energy-saving measures.

Following Marmox's CPD on thermal bridging, the architects recognised the importance of accurately assessing these junctions and contacted Marmox Technical Support for assistance.

Technical Support

Having completed specialist training in thermal bridge modelling, Marmox Technical Support Manager Martin Bass was able to calculate project-specific Ψ-values using recognised two-dimensional thermal modelling software.

Working from the architect's construction details and U-value calculations, Marmox produced bespoke Ψ-value calculations for the wall-to-floor and roof-to-wall junctions relevant to the project's SBEM assessment.

The Results

One of the wall-to-floor junctions demonstrated the value of undertaking project-specific calculations.

The calculations showed that replacing the default value with an accurately modelled junction substantially reduced the thermal bridge heat loss. Incorporating Marmox Thermoblock further improved the junction performance, reducing the Ψ-value by over 98% compared with the default SBEM figure.

For buildings with significant lengths of wall-to-floor junctions, improvements of this scale can make a meaningful contribution towards achieving compliance while reducing the need to compensate elsewhere within the building envelope.

Actual construction detail

Wall to floor example: SBEM default Ψ-value: 0.360 W/mK, this is where no evidence of a calculated Ψ-value has been done.

Calculated Ψ-value: 0.150 W/mK

Wall-to-floor junction with Marmox Thermoblock (100 × 65mm)

Calculated Ψ-value: 0.055 W/mK

Thermal model shown below, with the Marmox Thermoblock highlighted in red.

Wall-to-floor junction with Marmox Thermoblock (100 × 140mm)

Calculated Ψ-value: 0.006 W/mK

Thermal model shown below, with the Marmox Thermoblock highlighted in red.

Client Feedback

The CPD itself received excellent feedback from attendees.

"Lots of positive comments after – particularly noting how good it was to have an expert in who clearly knows what they're talking about and explained everything in detail."

Following the presentation, the practice commented:

"The CPD was really interesting and I never realised the impact that Ψ-values could have. At this point we are looking for every opportunity to improve our model... We discussed the default values used by assessors, and our assessor has used default values."

After reviewing the initial calculations, the client added:

"This is really interesting to see and very positive!"

The Outcome

The project demonstrates the value of combining technical education with practical engineering support.

Rather than relying on generic default values, the design team was able to obtain project-specific thermal bridge calculations based on the actual construction details. This provided greater confidence in the building's thermal performance and highlighted how incorporating Marmox Thermoblock could significantly reduce heat loss at critical structural junctions.

For architects and specifiers, Marmox offers more than high-performance construction products. Through accredited CPDs and specialist thermal bridge modelling, we help design teams understand, quantify and reduce thermal bridging, supporting more energy-efficient, compliant buildings.

Need Help With Thermal Bridging?

Whether you're looking to arrange a Thermal Bridging CPD or require project-specific Ψ-value calculations, the Marmox Technical Team is here to help.

As part of our technical support service, we provide project-specific Ψ-value calculations free of charge, helping architects, specifiers and contractors accurately assess thermal bridging and optimise junction performance. Our team can provide practical guidance to support your next project, from the design stage through to specification.