Addressing Condensation in Self-Storage Buildings

“Your roof is leaking! My stuff is soaked!” Unfortunately, this is not an uncommon complaint in self-storage facilities. Many times, the roof is not leaking, but condensation is dripping down on the contents below. Metal has become the industry standard in self-storage due to its durability, attractiveness, low maintenance and ease of use. However, without taking the proper precautions, metal roofs can have problems with condensation.

What Is Condensation?

Condensation is a natural phenomenon in which water vapor in the air is returned to its liquid state. All air contains water vapor in differing amounts. When air is cooled, the amount of water vapor it can hold is reduced. The point when it becomes too cold for the air to hold its moisture level is called the dew point. If the air is saturated, it will release this moisture in the form of droplets until such point as it is back below the dew point or the temperature goes back up. (See “Condensing the Facts.”)

For our purposes, condensation depends on three factors:

• Temperature inside the building
• Temperature outside the building
• Relative humidity (amount of moisture in the air)

Metal-roofing panels are not good thermal insulators, so as the cold outside air hits the roof panel, it cools. When the relatively warm moist air inside the building meets the cold metal-roof panel, the dew point is reached and water condenses on the underside of the roof panel, causing water to drip on the contents below.

Why Worry?

You have a well-written rental agreement that excludes water damage, so why worry about condensation at all? Maintenance issues cost time and money. They also can lead to unhappy customers, which ends up costing more money. Worse, rumors of dissatisfaction can spread fast.

In a perfect world, there would be no complaints and no maintenance worries. All we would have to do is worry about getting to the bank in time to cash all the checks from our full facility. But it only takes once for conditions to be just right for condensation to wreak havoc.

The good news? If you take this into consideration in your building plans, you can minimize headaches with a little preventive medicine.

Combating Condensation

The traditional way to deal with condensation is to keep the temperature on the underside of the roof panel from reaching the dew point. This is accomplished through the use of insulation. A vapor barrier is added to keep the moisture in the air from reaching the roof panel. In the building process, a vapor barrier is spread over the purlins, and insulation is rolled on top of that. Then, the roofing is attached on top.