Buildings that utilize steel in the frame and stud construction are very strong, durable and long-lasting. In the event of a fire, the steel framework may remain when a fire has taken the rest of the walls and surrounding fibers. When the steel frame remains relatively undamaged, it allows the property owner to rebuild quickly over the original steel structure. The downside is that steel tends to sap the heat value from insulation, so building codes have been developed by region to increase heat efficiency through the use of continuous insulation. Here are the zones and the minimal insulation values expected for continuous insulation products and steel structures.
The Eight Zones
The U.S. is divided into eight climate zones that, in some areas, overlap a little. The higher the number (e.g., 6, 7, or 8) the greater the R-value and thickness required for the continuous insulation needed. Typically this means that the hotter, more tropical regions (like the Southernmost tip of Florida) require the very least R-value for this type of insulation, and the frigid temperatures of Alaska require the greatest R-value of insulation to keep steel buildings warm. Pockets of the country, such as the mountain region of Northeastern California, will require thicker insulation than most of the rest of the state.
The Suggested R-Values by Region Number
One website allows you to select the state in which you are working and find the minimum R-value requirements for the insulation you will need. For example, Wisconsin is composed mostly of Zone 6, which requires a 20 R-value, although it is highly recommended that a much higher R-value is used. The Northern part of Wisconsin falls into Zones 7 and 8, which needs a 21 R-value because this part of the state tends to be several degrees colder in winter than the rest of the state. Conversely (and for comparison value), Zone 1 in the Southernmost part of Florida only needs a 3 or 4 R-value insulation to maintain the correct amount of heat in Florida's cooler months. States in between these two extremes will need R-value insulation between 5 and 19.
If you want to make sure that your steel home or commercial building passes inspection and passes the minimal requirements for continuous insulation, be sure to utilize a continuous insulation product that bypasses the minimum requirements. An example of this would be to use insulation with an R-value of 39, keeping in mind that the steel will sap the insulation's efficiency by half. Hence, almost double the R-value of insulation in a steel structure building would make the insulation almost exactly what the state and zone codes require.