Anytime the emmisivity is reduced the radiated heat is reduced. Make a surface bright and shiney - like chromed and it will reduce the emmisivity. Reducing conduction is what an insulating material can do.
This is where the science is. ^^^
When we have a new product development at work that is having thermal issues, i.e. not able to get the heat out of the box, we will paint the inside flat black. Typically we gain ~8% in reduced core temperature. Same thing works in reverse by using bright or polished finish there is less emissivity of radiated energy, the heat won't go in or out. Header wrap acts just like the insulation in your house. The material blocks thermal conduction.
An IR thermal temp gun makes it easy to prove to yourself. Shoot something polished on your engine that is bolted to something black or unpainted. The temp readings will be significantly different, event though the surfaces are the same temp and will burn you just as bad.
