Steel vs Carriage House Garage Doors

What Carriage House Means

Clopay builds its Coachman carriage house doors from insulated steel with woodgrain composite overlays, and C.H.I. Overhead Doors builds its Carriage Collection on a steel section with composite face boards laminated to it. Both open overhead like any sectional door.

The style and the construction are separate choices. Clopay sells carriage house doors with insulation as an option, and others with polyurethane insulation as standard.

Wood, Composite, Fiberglass and Aluminum

C.H.I. describes wood as strong and easy to repair, and also as a material that warps and splits with changes in temperature and moisture and needs sanding, staining and resealing about once a year.

Composite overlays put a molded wood-look face over a steel core and are made to resist the warping, cracking and rot that affect real wood. They can be painted or stained.

Fiberglass gives a wood-grain look without warping, and a damaged fiberglass section has to be replaced. Aluminum does not rust and holds its color in the sun, and it dents more easily than steel in hail.

Polyurethane and Polystyrene Insulation

Polyurethane foam is injected between the steel skins, fills the whole cavity and bonds to them, which makes the door stiffer and quieter. Polystyrene is a rigid foam board fitted between the layers. It is lighter and the lower-cost option.

Clopay publishes an R-value of 18.4 for one of its door lines with 2-inch polyurethane, and 6.5 for the polystyrene version of the same line.

R-Value and U-Factor

DASMA, the door makers association, says the two numbers are not comparable. The R-value printed on a garage door is calculated for one section through its center. The U-factor is measured in a lab on the whole door, including the joints, seals and hardware where heat escapes.

DASMA treats U-factor as the more accurate figure, and the International Energy Conservation Code sets garage door requirements by U-factor. When a manufacturer publishes a U-factor, compare doors on that.

Attached Garages in a Cold Climate

The Department of Energy's Building America program treats an attached garage as outside the home's insulated envelope. Walls and ceilings shared with the house need to be insulated and air-sealed together, to keep out both cold and car exhaust. This matters most with a bedroom or bonus room over the garage.

An insulated door with good weatherstripping keeps the garage itself warmer in winter. DASMA also publishes wind load guides, and the local building department decides what wind rating a house needs.