Construction layers
The more construction layers your door has and the thicker it is, the greater the R-value will be which can help maintain your garage’s temperature. This is important if the garage is attached to your home or used as a living space.
1-layer
Steel with no insulation. Since there is no insulation layer, there’s no R-value.
2-layer
For a more insulated, quieter garage, your base layer is steel, plus you have a layer of insulation. Good R-values.
3-layer
This is the toughest, most energy-efficient option with the best noise reduction. Steel exterior plus insulation and an interior layer of steel. Best R-value.