Our garage door probably is the original one in our 30-year old house,
and I am wondering what the R-value is likely to be.
The exterior is wood, and the interior looks as though it could be
Masonite. The door is a couple of inches thick, but I have no idea
whether it is hollow or whether it has insulating material in between
What is likely to have been used in those days, and what kind of R-value
might it have?