Replies

1. 
   walta100 | Jun 03, 2017 10:27pm | #1

   The only reason to insulate any space is if you plan on heating or cooling that space.

   So from a return on investment point of view it is not worth the expense.

   The insulated doors do rattle less and if someone sleeps over this door when you need to come and go an insulated door may be worth a lot.

   Walta

2. GBA Editor
   Martin Holladay | Jun 04, 2017 06:02am | #2

   J.,
   Your question confused me at first -- I thought that a "R13 VS R8" was a seven-digit model number for some type of heating equipment. Then I decoded your message to mean, "an R-13 door versus an R-8 door."

   Walter figured out your meaning before I did. Walter's point is a good one. That said, it would have been helpful if you had shared your climate zone or geographical location.

   By the way, R-value claims made by garage door manufacturers are almost all fictitious. For more information on this issue, see Energy-Efficient Garage Doors.

3. 
   charlie_sullivan | Jun 04, 2017 09:03pm | #3

   Get the R8. The insulation does help for an attached garage, both to keep the garage warmer and, as a result, to reduce heat loss from the house. But:

   1) The actual performance won't be as good as those numbers indicate, as explained in Martin's link, and the difference will be smaller than the difference in ratings, and

   2) Assuming those are both 2" thick, but one has EPS (expanded polystyrene) foam and the other has polyurethane foam, the main difference in R value arises from the gas the fills the tiny cells of the foam. However, over time, that gas will diffuse out and be replaced by air, and both doors will settle at about the same R-value.

   3) The gas used in the polyurethane bubbles is a potent greenhouse gas, 1400X worse than CO2. In some cases, you might overcome the climate damage done by that gas through the energy savings, but not in this case.