There is a thread that was started a while ago about this.
Hood blanket... literally?
I'm currently working on sealing up my engine compartment(slowed down by the 1/2in of ice we got recently). I already put in a gasket around the hood itself. Which I've seen a decent improvement from that alone. So if you've got a garage unlike me, I say go for it
I found this stuff at lowes that might be worth looking at
Reflectix 16" x 25' Foil Insulation they have it up to a 4' wide roll if you need it.