Detailing - Specification

Euroclad

Introduction

In a more revolutionary step, the new regulations also require the calculation of the heat loss through all the details of the building envelope. The thermal efficiency of the ridge, eave, gable, window, door junction, cills etc must all be calculated. Their propensity to create condensation is also evaluated as a result. Two new criteria have been recognised.

PSI ( ψ ) values

The new three-dimensional thermal models not only calculate the U-value on the plane elements, they are also able to produce psi and ‘f’ factors for all junctions and details. The psi value reflects the additional heat loss through the detail per linear metre, when compared to the plane elements. The Building Regulations require the heat loss through the details to be included in the evaluation of the building’s total thermal performance. There is no need to achieve the lowest possible psi values, it suffices that the efficiency of the details are calculated and can demonstrate compliance with IP17/01 (5.1).

Calculation of ‘f’ factors

With the introduction of reduced air leakage requirement there was concern surrounding the possibility of condensation forming on the internal surface surrounding a thermal bridge. The propensity to create condensation is a function of the detail’s thermal inefficiency and the temperature/humidity of the environment within the building. Software pre building’s use and its internal humidity can lead to easy identification of any detail’s acceptability. The ‘f’ factor is simply compared to the minimum allowable for that classification of building. Dramatic changes in ‘f’ factors can be achieved by small alterations in the design. The ‘f’ value has only to exceed the minimum requirement.

Also available is our Design and Installation Recommendations - for Built Up Metal Twinskin Roof and wall systems.

Design and Installation Recommendations