Water is your enemy. It doesn’t matter whether you build with concrete, wood, or steel. Water can infiltrate concrete and freeze, creating cracks. It rots wood. It corrodes metal. No matter what you choose to build with, you’ve got to deal with this enemy.

Quality design and manufacture—the hallmark of Miracle Truss® steel buildings—seals out water and snow. Exterior protection, though, is only half the battle.

Water Vapor

It’s in the air, inside and outside. Water vapor is always present, and you’ll have problems if this water vapor condenses into liquid water inside your finished walls.

If you remember your high school science, water vapor condenses with it comes into contact with something colder than the surrounding air temperature. You usually see this with single-pane windows. Water droplets form on the interior surface of the window.

What you may not realize is that this isn’t just an occurrence you have to worry about during the winter months. Even in the dry winter months—when the relative interior humidity may be only about 30%, you’ll get condensation if the room’s temperature is 68 degrees and the outside temperature is 35 degrees or less.

However, if you live in an area with high humidity—say above 80%–the temperature outside only has to be as cool as 63 degrees for condensation to form. Wow. Science.


The purpose of your building may make condensation something you don’t have to worry about. This is especially true if you don’t plan to have any form of interior heating or cooling—and that’s usually also because you don’t have any reasons to add interior walls to your Miracle Truss® building.

If heating or cooling your building is necessary, and you plan to finish the interior, you’ll definitely want to put up a vapor barrier. This helps to minimize the infiltration of humid air into the interior wall assembly.

For this reason, it’s best to attach insulation to the exterior siding. This helps to isolate your interior wall from the exterior temperature, and helps to prevent condensation. It also helps you conserve on energy because you’ll prevent thermal leaks, cutting down on the cost of heating and cooling.

Quality metal siding properly installed and joined edge to edge creates an interlocking seal against moisture and air convection. It creates a thermal break between the interior and external metal faces of the metal. The addition of the vapor barrier, as well as insulation is highly effective at minimizing condensation on the insides of your walls.

Your inner wall stays close to the ambient interior temperature, while the exterior metal exposed to the outside temperature remains close to that temperature. Little or no humidity in between means there’s a very low chance of condensation.

Miracle Truss® building designs make it straightforward to create interior framing for walls with standard 24-inch on center studs. You’ll be able to roll standard batting insulation. You can read more about the benefits of building with Miracle Truss® here.

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