The last post talked about how heat flows or transfers from one object to another through the process of conduction, convection, or radiation. Insulation is installed in a pre-engineered steel building mainly for the purpose of maintaining a comfortable temperature inside the metal structure.

Whether you are buying insulation materials from a lumberyard or from a steel buildings manufacturer, you will notice that the materials are labeled with performance ratings called R-Values.

A material’s R-Value is the measure of its ability to resist heat flow. Therefore, the higher the R-Value, the higher the material’s insulating effectiveness or thermal resistance.

The mathematics of determining the R-Value of your steel building’s insulation depends on the type of insulation used – the materials, their thickness and their densities. For example, a 2-inch thick insulation board has twice the R-Value of a 1-inch thick board.

The R-Value of the insulation for a pre-engineered steel building that is installed in a multi-layered style is computed by adding the R-Values of the individual layers. Installing additional insulation in your steel building increases its resistance to heat flow or the R-Value.

The amount of insulation or the R-value that you need depends on your climate, type of heating and cooling system, and the size of the area you plan to insulate.

Insulation reduces unwanted heat loss or gain and can decrease the energy demands of heating and cooling equipments. The equation below calculates heat loss using R-Values.

(Steel Building’s Heat Loss) = [(Steel Building’s Total Surface Area) /   (Surface Area R-Value)] x (Temperature Difference)

Temperature difference means the difference in temperature expressed in degree Fahrenheit on the two sides of the steel building’s surface, typically interior and exterior.

The steel building’s total surface area is expressed in square feet. The surface area R-Value is the R-Value of the surface being evaluated such as an insulated wall. Heat loss is expressed in BTU’s (British Thermal Unit) per hour.

It is important to know the R-Value of the insulation material for your pre-engineered steel building because some states require a minimum amount of thermal resistance for roof systems of commercial, industrial, and institutional buildings.