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.

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.

Concealed Condensation

Concealed condensation is the most difficult to deal with and can be the most damaging to any kind of structure. This type of condensation may be controlled in metal buildings by the proper ventilation. Additional condensation control can be accomplished by venting the cold cavities of the walls and roof.

Secondary Framing

Secondary framing is created from rolled steel coated with a red-oxide primer finish in gages from 12 to 16 to provide an extremely rigid, and corrosion resistant structure. The following elements are formed as secondary framing:

Girts (walls) & Purlins (roof): These members run the length of the building providing rigidity, and a sturdy skeleton to attach the sheeting. They are rolled from steel coils 12,14 or 16-gauge steel, or thicker if needed. All girts and purlins are pre-punched for ease of assembly.

Eave Struts: This is a rolled member formed into a "C" to match the pitch of the roof. The eave strut is also made of 12, 14, or 16-gauge steel.

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.