This is a fog and condensation material created in Cycles. This .blend only contains the material NodeGroup and the Particle System of Droplets, but I have also created an add-on to control and customize the Material.
To download the add-on with the Material, go to: http://www.blenderskool.cf/fog-material-addon/
Textures used from http://www.textures.com
Some great thinking behind this node setup, thank you, but I am trying to use it acting on glass rather than on a mirror - in other words the reflections/image you see in the plane should be what's behind the plane rather than in front of it. It's the difference between condensation on glass and condensation on a mirror- not easily supported with the node setup as it stands. I've tried mixing transparency shaders and playing with the node setup but not realistically yet....any help appreciated.
Great work!! thanks