DASMA TDS 195 - Condensation on Garage Doors: Causes and Solutions

Water dripping off a garage door on a winter morning looks like a leak. It is almost always condensation. DASMA TDS 195 explains the physics and what actually helps reduce it.

What this data sheet says

DASMA TDS 195 identifies condensation on garage doors as a moisture and temperature phenomenon, not a door defect. Condensation forms when the door surface temperature drops below the dew point of the surrounding air. Cold steel and warm humid air are the two ingredients.

"Condensation on a garage door is caused by the surface temperature of the door falling below the dew point temperature of the surrounding air. This is not a manufacturing defect."

The TDS covers three common scenarios:

• Interior face condensation in winter: warm, humid air inside the garage hits the cold inner steel skin. Insulated doors can still develop condensation if the inner skin temperature falls below the interior dew point.
• Exterior face condensation in the morning: on clear nights, the outer skin radiates heat to the sky and cools below the outdoor dew point. This is the same process that frosts car windshields.
• Floor puddles near the bottom seal: cold air seeping under the seal meets warmer floor air. Moisture falls to the floor near the bottom of the door.

Higher R-value insulation raises the inner skin temperature. This reduces interior condensation. It does not eliminate it when humidity and temperature conditions are severe.

When it applies

Colorado is a dry climate overall. But garages can be surprisingly humid. Here is why this matters on the Front Range:

• Vehicles with snow melt onto the floor and raise interior humidity sharply on winter mornings. A two-car garage can briefly reach 60 to 70% relative humidity while outdoor temps hover at 20 degrees.
• Denver's clear nights accelerate skin cooling through radiative heat loss.
• Attached garages sometimes receive warm moist air from the house through gaps in the common wall.

What this means for you

Ventilation is the most effective long-term fix. A passive vent or small exhaust fan reduces moisture buildup. Ventilation also matters for carbon monoxide safety. TDS 173 covers garage ventilation in detail.

Insulation helps but does not fully solve the problem. An insulated bonded-core door raises the inner skin temperature. It reduces the frequency and severity of condensation. It does not prevent condensation in extreme cold with high humidity.

Do not mistake condensation for a seal failure. Water forming on the door face and dripping down looks like infiltration. If it only happens on cold mornings with no rain, it is condensation.

If you see persistent moisture and are not sure of the source, G Brothers can assess the door's insulation and seal condition across the Denver metro area and Front Range.

Full text and source

Download DASMA TDS 195 from the official TDS index at https://www.dasma.com/technical-data-sheets/.

This entry covers condensation on residential sectional garage doors. Water infiltration under the bottom seal from precipitation or ground water is a separate topic addressed in DASMA TDS 197.