fRsi calculations
Surface temperature evidence for your construction details, with a clear report for building control and your design team.
Checking the coldest part of the detail
Insulation can perform well across a wall or roof while a junction has a much colder internal surface. That local temperature matters when assessing the risk of surface condensation and mould.
The fRsi temperature factor describes the internal surface temperature relative to the internal and external conditions. We calculate it using the junction model and assess it against the criterion appropriate to the project.
The assessment follows the relevant conventions in BS EN ISO 10211 and BRE guidance. The report states the conditions, assumptions and assessment criterion used.
Included with your junction calculation
Our standard service includes the Psi-value and fRsi assessment. If building control has specifically requested surface temperature evidence, send us the request with your detail.
£150 for the first standard 2D junction, then £100 per additional detail on the same project.
Send your detailA focused assessment
This assesses surface temperature and the risk of surface condensation and mould at the modelled junction. Moisture movement within the construction, on-site damp investigations and whole-building humidity problems need a different assessment.
If the detail needs improving
We'll explain the result and discuss where changes to insulation continuity, materials or geometry could help. Advice and reasonable minor revisions are included.