How Does Condensation Form?
Condensation forms when warm, moist air collides with cold surfaces. The cold surface cannot hold the excess water and so condensation forms on the surface such as the underside of your metal roof or decking.
Most often, you will see this happening on the interior of your windows, your windows act as a barrier between the interior and the exterior of your building.
Think of this, it is a cold winter morning and you’re starting your car. The outside of your windshield is cold, so when you turn on the heat to warm it up your car you’re also warming up the inside of your windshield.
The warm air from inside your car heats the windshield until the outside of the windshield starts to warm up. The cold air outside the car meets the warming windshield and condensation forms. To get rid of the condensation or “fog” you need to turn on colder air to lower the windshield’s temperature and offset the difference between the outside ad inside windshield temperatures.
Here is a different example of condensation that is a little more serious!
Turning on the shower creates hot moist air to come into contact with the colder bathroom walls.
That contact causes condensation on your walls and may drip from the ceiling also.
What is really happening is that warm, moisture-laden air is trying to drive its way out of the bathroom toward drier areas and when it hits a cold surface the moisture condenses.
Metal roof and panel excessive condensation can cause damage to your building and can become costly, damage such as:
- Wet ceiling and wall insulation
- Stained ceiling tiles
- Overhead electrical fixture damage
- Roof joist damage
- Structural damage
There are three primary things that work together to avoid condensation in buildings with metal roofs or exposed metal decking.
Insulation and Air Sealing. Install the correct amount of insulation on top of the acoustical ceiling tiles (ACT) system, also make sure that there are no air leaks from the work space into the attic area.
You need to keep the warm air from getting into the attic area.
A Vapor Barrier. This will stop the transmission of water vapor from the work space into the attic. This vapor barrier is usually best directly on top of the ceilings and beneath the insulation. By placing a vapor barrier beneath the roof deck or roof panels all that will do is transfer the problem from the underside of the roof to the underside of the vapor barrier.
Ventilation. Good attic ventilation brings in fresh air at the bottom of the attic and above the ceiling and uses convective airflow to exhaust it out at the ridge of the roof or at both ends of the building through exhaust vents. As the air travels through the attic, it picks up moisture and carries it out.