Thermal bridging and condensation risk analysis, Southwest Land

Hill Partnership reached out to us to help them determine the best type of insulation to use at three plots of their proposed development in Southwest Land, London.

Key details

Project name

Thermal bridging and condensation risk analysis, Southwest Land



Hill Partnership




Services provided

- Thermal bridging and condensation risk analysis


Hill Partnership needed to meet building control requirements to enable them to successfully complete the detail design of the development at construction stage.   

Our assessment had to take into account the limited space for the additional insulation underneath the balconies, but also the increased thermal conductivity of Rockwool Hardrock compared to XPS insulation. We also carried out the new U-value calculation to ensure that the external wall complies with the design stage U-value.  

To meet building regulations, we used HEAT (2D) modelling software to calculate the Psi-value (heat flow) and the internal surfaces temperature factor (fRsi­­) in accordance with ‘BRE 497 – Conventions for Calculating Linear Thermal Transmittance and Temperature Factor’.

Affordable housing development


Our analysis showed that the Psi-values (ψ) and temperature factors (fRsi) perform better than the Standard Assessment Procedure (SAP) default value. It’s the only government approved method for calculating the energy performance of dwellings.

We proposed that an additional 30mm Rockwool insulation underneath the terrace parapet above the commercial units should be used to eliminate the risk of condensation. Our findings helped our client meet the building control requirements by offering a comfortable and healthy indoor environment in the proposed dwellings.


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