Condensation. Sweating. Raining inside... All of these terms are used to describe a common concern with metal buildings. What do you do to get rid of the moisture build up inside a metal building?
First let's clear up a common misconception. Moisture is not a bad thing, it's a natural part of our environment - lots of things get wet and dry out every single day, including metal buildings. The issues arise when things get wet and stay wet for extended periods of time.
If you have a metal building that is continuously accumulating moisture inside faster than it can dry out, or it is producing so much condensation that it appears to be raining inside and damaging your property, then it's time to decide what to do.
At a simplistic level, there's really only two options for dealing with moisture in metal buildings:
1) Dry the building out quickly with ventilation whenever condensation occurs.
2) Seal the building up air tight and and create conditions that impede/prevent condensation from happening in the first place.
We discuss the basic metal building insulation guide on our site and we also have an in-depth page about Moisture in Metal Buildings, but this page is meant to be a quick summary of how to address this problem.
Dry the Building Out
Using either active or passive ventilation, move air from outside through your building to keep things dry. You can use fans or just open windows and doors, but you should have enough outside air moving into the interior of the building, which pushes relatively warm-moist air inside the building to the outside. When the interior air temp of the building is equalized (or close to) ambient temp, it will be almost impossible for condensation to occur with less than 100% relative humidity.
Pros of this approach: it's simple to do (opening doors/windows) and is low (zero) cost.
Cons of this approach: the building could be hot inside (ambient during summer) or super cold inside (during winter) with this approach, so it may not be usable on some days.
Add a Vapor Barrier and Seal The Building Up
As we discuss on our Moisture in Metal Buildings Guide, if you can seal up the metal building and create a new, interior layer that can stay warmer than the dew point, you can stop condensation from forming inside your building. In this method you use BlueTex™ insulation as your new interior (instead of the inside surface of the exterior sheet metal) and you install it according to our instructions, sealing up the seams air tight. This new layer is a different temp than the exterior metal so it reduces the chance of moisture forming in the first place when you are are occasionally heating/cooling the space in semi-conditioned buildings.
Pros of this approach: You can use heating/cooling in your building on those days when you need it, no matter what the temp is outside. This means your building can be used year round.
Cons of this approach: It's more labor intensive and requires an investment, but both pay off almost immediately when you consider the comfort and usability of the space.
No matter which way you go (option 1 or option 2), you can reduce or stop moisture in a metal building with a few simple steps and a little building science knowledge. If you still have more questions, check out our Ultimate Guide to Moisture in Metal Buildings.