Controlling Condensation

Two things must be present for condensation to occur: warm moist air and cool surface temperatures below the dew point. The proper control of these two factors can minimize condensation.

In metal buildings, we are concerned with two different areas or locations: visible condensation which occurs on exposed surfaces below dew point temperatures, and concealed condensation which occurs when moisture has passed through the vapor retarder and into interior roof and/or wall cavities and then condenses on a surface below dew point temperature.

Heat Transfer

Effectively controlling temperature in a steel building requires insulation to be present along exterior walls and roof. When a temperature differential is present in an enclosed steel building, heat will work from warmer areas to colder areas until the temperature in the building has stabilized. At the point of thermal stabilization, the cooler (and heavier) air will be present at lower elevations and warmer air will be present at the roofline. The function of insulation is to help stabilize air temperature at more desirable levels. When it is hot outside, preventing heat from transferring into the building is the goal, and of course in the winter we want heat to remain inside.

Heat transfer occurs in three ways:

Conduction : Occurs in a solid or liquid when heat from one object is transferred by touch to another object. An example of this occurs when a pot on a stove will heat up by conductive heat transfer from an electric coil.

Convection : Occurs with the physical movement of air. There are two types of convectional heat movement. The first is natural, where hot air rises displacing the cold air and moving it down. The second type is forced or mechanical convection. This occurs when an object, like a fan, physically moves or "forces" the air to move.

Radiation : Occurs when an object is warmer or hotter than the air around it. For example, the sun, which is hotter than everything around it, radiates heat waves that travel through the air and is either absorbed by or reflected by the surface it comes in contact with.

Surface Air Film Coefficient (F)

The amount of heat flow in BTU's per square foot per hour between an exposed surface of a material and the adjacent air. It is the measure of the conductance of heat through the air film that clings to all surfaces.

Overall Heat Transmission Coefficient (U-Value)

A unit used to express heat passage through a complete building section, including air films. U-Values serve as a basis for determining transmitted heat loss. The lower the U-Value, the higher the insulation value.

Walk Doors

Walk doors can be provided as pre-assembled or knock down (field assembled). Metal Building Depot provides solid doors for both options in the following sizes: 3070, 4070, and 6070. The walk doors are typically keyed alike per project. Because of unknown variables, Metal Building Depot does not offer fire rated doors or doors to fit in masonry.

Features of the pre-assembled doors are as follows:

Foam insulated specifically designed for metal building use. Pre-assembled and self-framing for ease of installation. No framed opening required if Metal Building Depot standard girt spacing is utilized. Doors are finished in a two-coat primer; color selection is white or bronze. Doors are shipped in wood crates for protection. All doors have Grade 2 lever locks as standard. Hinges are ball bearing and powder coated. Insulated jambs. 3070 and 6070 doors are made of 20-gage material, 18 gage is available.

Features of the knock down doors are as follows:

Foam insulated specifically designed for metal building use. The walk door is shipped knocked down for field assembly. Doors are textured 20 gage galvanized prime painted and pre-finished in either white or bronze. Weather stripping and standard entrance lock is included. The walk door package is shipped with polybag and full cardboard carton. All doors have Grade 2 lever locks as standard. Hinges are ball bearing and powder coated.