What a cool idea. New thinking. I like it. But in line of logic with what Frank Lee says above, have you thought about the possible down sides? I wonder if a removable, insulated cover for the valve cover would be better for the warm months. Secure it to the valve cover using "plumber's tape," perhaps?
Here in Cali, it would have to be removable. Insulation like that would probably be an instant fail on emissions testing. All such mods need a CARB sticker to pass.