Not much at all. I have used this technique in a few things like RC cars and airsoft many many times in the past and never seen any overheating issues. You only want to add two layers of it, and when it dries, it is very thin. I know it will hold a little more heat, but it is a very slight difference, and you wouldn't even be able to tell a difference without equipment to measure it.I wonder what Thermal Insulating effect nail polish May or May Not have on a mod's Board?