How Psi Values can affect the road to compliance

As a result of changes to the building regulations in June 2022, Psi Values now need to be properly calculated if your project is to successfully comply. We can no longer rely upon using Accredited Construction Details (ACDs) to achieve compliance on the fabric efficiency of the property.

Read more: SAP 10 – What you need to know about Psi Values

If the Psi Values are not calculated and the development is not going ahead with pre-calculated Psi Values then the details have to be manually calculated per development.

In the development below, the Fabric Efficiency of the dwelling is failing due to the default linear junction values being used.

When the thermal junctions were manually calculated by C80 Solutions, this product is down the fabric efficiency rating in line with compliance, as seen in the figures below.

The junctions calculated in this case were: Block and Beam Floor, Sloped Roof at Ridge, Flat Roof at Eaves, Ground Floor to Wall, Timber Reveal, Sloped Roof at Eaves.

This shows how much of an improvement calculating thermal bridging can have on an assessment, bringing a hard fail to a pass.

For reference, here are the default junctions with the calculated junctions:

Our expert, qualified team is ready to help you calculate Psi Values and help you with all aspects of SAP 10 compliance. Give us a call on 0113 258 8445 or email

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