Cold Bridging (external insulation base profile)

External insulation ticks many boxes but cold bridging still takes place at the base profile.

A 1.5mm Aluminium base rail has the same conductivity as the 8 m of polystyrene or rockwool insulation above it.

Since heat takes the path of least resistance. The area of wall affected by the cold bridge extends beyond the L shaped mounting surface.

This obviously applies to stop-tracks and over-sills. Average U-value calculations should consider the mounting area of these items.

Consider using Stainless Steel that has almost 1/13 the thermal conductivity of Aluminium.