Garage Door Insulation R-Value Explained

R-value is a number that shows how well a material resists heat flow. A higher number means better resistance. You will see it on insulated garage door labels.

What the number tells you

The number comes from the insulation inside the door panels. It does not cover the whole opening. Gaps at the sides and top and bottom let heat escape. Seals matter as much as the panels.

What insulation is made of

• Polystyrene. Rigid foam boards fitted into the panels. Often found on lower priced doors.
• Polyurethane. Foam injected between layers and bonded to them. It tends to make a stiffer door.

When insulation matters most

• The garage is attached to the house.
• There is living space above or beside it.
• You use the garage as a workshop or gym.
• You want the door to be quieter.

If the garage is detached and unheated the gain is smaller.

Other things to look at

1. The bottom seal.
2. The side and top seals.
3. The panel thickness and steel gauge.
4. The warranty.

Do not compare numbers alone

Different makers measure R-value in different ways. Ask how the number was found. Ask what the door is made of.

If you plan a new door read [when to replace a garage door](post:when-replace-garage-door). See our page on new garage door installation.