Detailing
To help customers better understand the
thermal performance of metal clad
buildings we have prepared
Construction Details, showing thermal
efficiencies of joint details and plane
elements using three-dimensional models.
These details help illustrate the overall
thermal performance of a roof or wall as
well as the specific heat loss through
details per linear metre.
Amendments to Building Regulations Approved
Documents L2 (ADL2) came into effect in April
2002 and impose significant new criteria on the
construction of metal buildings. The requirement
to reduce CO2 emissions and produce thermally
efficient buildings has a significant effect upon
the construction of the building envelope.
Essentially, U-values have been reduced for both
roof and walls, but more significantly, the method
of calculation is now much more rigorous.
Complete analysis of the plane elements is now
mandatory.
The software used to model the detrimental
affect of any thermal bridges is now quite
sophisticated and therefore gives a much more
realistic reflection of the actual thermal
performance of the total building envelope.
Several different programmes are available
(both BRE and Euroclad employ TRISCO) but to
be compliant, the model must satisfy BS ISO
EN 10211-2. This is the required standard for all
compliant three-dimensional thermal models.
Specification and Installation
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.
Shown below are examples of typical details for a Euroclad Standingseam roof system. They can be viewed as 3d PDF files or you can download them from the CAD Downloads section of the web site.
Euroseam Typical Eaves |
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Euroseam Typical Eaves - with bullnose |
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Euroseam Typical Ridge |
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Euroseam Typical Verge |
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Typical Details
Built-up roof constructions
Built-up wall constructions
Corner details
Ridge/Hip details
Gable/Verge details
Mono ridge details
Roof abutment to side details
Roof abutment to end and
apron details
Valley/Parapet gutters and
Internal hips
Eaves gutter details
Door and window head details
Door jamb details
Window jamb details
Cill and drip details