Most older garage doors don’t provide a good seal. They block rainwater but were not designed to block air leakage. With many people heating garages today, both insulation and blocking air leaks through and around the garage door are important.
Most attached garages have two walls common with the living area. A more efficient garage door will moderate the garage temperature swings and reduce heat loss during winter and heat gain during summer.
When you compare air tightness of garage door designs, pay attention to seals between the panels. The simplest types are compression seals that compress metal spring seals or polyurethane bulb weatherstripping in the gaps. The seal can take a permanent set over time and not seal as well as initially, but this design is less expensive than others.
The most effective seals use a tongue-and-groove or shiplap panel edge design, often with a smaller flexible compression seal. These designs create a longer, non-straight air leakage path, providing a long-term seal.
Deciding on insulation
Most insulated garage doors use polyurethane or polystyrene foam insulation. A 2-inch-thick door, filled with injected polyurethane foam, can have insulation greater than R-20. When choosing a steel door (not needed on a fiberglass door), select one with a polymer thermal break between outdoor and indoor metal skins to reduce heat loss. A thick 27- to 24-gauge (lower gauge number is thicker) galvanized steel skin will last decades.
A simulated wood-clad insulated steel garage door is much more efficient than a solid real wood door—and more maintenance-free. A half-inch-thick polymer coating is applied over the exterior steel skin, then authentic wood grain is molded into the surface to look identical to real stained wood.
JAMES DULLEY is a nationally syndicated columnist who writes on energy efficiency and do-it-yourself energy topics.