We've done it to a double wide panel door facing west, the garage was sweltering in summer and lost a lot of heat in winter. The laundry was in there, so it got used a fair bit.
The insulation was styrofoam panels that wedged into each of the panels of the door. Seemed to help a bit in summer, but I also should've added brushes to the sides to close the gap on either side.
We've done it to a double wide panel door facing west, the garage was sweltering in summer and lost a lot of heat in winter. The laundry was in there, so it got used a fair bit.
The insulation was styrofoam panels that wedged into each of the panels of the door. Seemed to help a bit in summer, but I also should've added brushes to the sides to close the gap on either side.