For those of you interested in upgrading a door, here's an article I wrote a few years ago. It's about adding 2cm vacuum insulation to an entrance door. The 2 cm vacuum insulation is identical to approx. 12 cm Rockwool.
The article is including infrared images (before and after upgrading).
It's in Dutch, but Google Translate can help...
Since I cannot post links yet, I try it this way:
http://www.olino.org/articles/2013/0...ok-voor-warmte