Still on the subject of spray-applied polyurethane foam insulation for steel buildings, the following steps have already been undertaken including determination of insulation thickness, selection primer, selection of a vapor retarder, and selection of the spray polyurethane system. The last step is to select either a protective coating system and a thermal barrier, the choice of which depends on the place of application of the insulation material.
When the SPF system is applied to the exterior surfaces of steel buildings, it is essential that the foam be covered with a protective elastomeric coating system. This enhances the durability of the foam system by protecting it from the sun’s UV rays and other meteorological phenomena. It is of utmost importance that the elastomeric coating must bond to the polyurethane foam, making the coating a basic part of the insulation system for steel buildings.
Elastomeric coating systems that are designed for use over foam insulation of steel buildings form a protective membrane that provides long lasting water-resistance.
In choosing the appropriate protective coating system, consider the physical and performance characteristics of the material such as:
· Resistance to inorganic bases, acids, alkaline materials, and hydrocarbon solvents
· Permeance to water vapor
· High elongation values
· Preservation of physical properties through the years
· Resistance to UV rays
· Resistance to hail impact
· Life expectancy
· Ease of maintenance
· Resistance to dirt pick-up
· Adhesion to the SPF
· Combustibility
· Attractiveness
On the other hand, if the SPF system is applied to the interior surfaces of steel buildings, it must be protected by a 15-minute thermal or fire barrier. This thermal barrier is designed to slow the temperature increase of the foam in the event of a fire and to delay the foam’s involvement in a fire.
In the choice of a thermal or fire barrier, consider the following:
· Building code requirements
· Adhesion to the SPF
· Existing environment where it is to be used
· Ease of maintenance
· Attractiveness
(to be continued)