This works well on keeping out heat, cold and also keeping out bright RV parks lights. We did this about 6 years ago, it has worked well for us. The only problem that we might have had with it is that our vent cover has become brittle and started crumbling. We have a Maxair over it, I have seen something in the past somewhere that heat might build up between the inside vent covering and outside vent lid and cause damage or breakage. Regardless we are still using the inside cover.
You can find the shiney covered bubble insulation at Lowes.
2006 Silverado 2500HD Duramax
2010 Prime Time Lacrosse 303RKS
2007 Hensley Arrow Hitch
PT Crew Member 125
Good Sam Club, Cedar Creek Sams Chapter
Passport America Member