Insulating a garage door some more?

[rtz]

It has 1" thick foam from the factory. It appears to have space for one more inch. Would it make any difference at all hot or cold if the foam was doubled up to be worth the money and effort?

 

[astroracer]

Does it get direct sun during the day? It may make a difference for cooling if it does.
For heating you probably will not notice it.
Mark

 

[rtz]

It faces the north and gets no direct sun on it.