Navi forum exterior cladding, how'd you make it "speed-fit" for the masses?

[wookey]

Baz - yes it can be that bad. Steel conducts 1000 times better than EPS/glassfibre. So a 1mm thick (full length) bracket conducts as much heat as 1m height of EPS/glassfibre. That's why thermal bridges really matter.  A bracket that only goes part-way through the insulation could be fine though. It's the full depth with no insulation that's the real issue.

( http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html )

[Robl]

Yes the steel is a really bad metal thermal bridge - but once you take into account that the outside is air and not a perfect thermal conductor I think it is less critical.  You can't get a wall/window with a U value greater than 6W/m^2/C, as that's all you get through the two air interfaces.  So a bit of metal, even copper, can only conduct so much heat to the air that it's nearby, and practically that will limit the U value rather than the metal itself.

I'd say the (1mm thick by) 100mm deep steel has a U of about 400, but in situ due to the outside air interface this is limited to U=23.  100mm of platinum EPS is about U=0.3, So in practice, the 1mm steel rail is equivalent to 1mm*23/0.3 = 77mm of EPS.  Not great, but not as bad as feared.