The types of insulation for the prefabricated panel industry have changed considerably through the last 50 years. So says Paul J. Erickson, president of Erickson Industries Inc., River Falls, Wis.

In the 1950s, Erickson explained, the primary insulation used was fiberglass semi-rigid batte. It had an R-value of 3.1 per inch. Common usage for normal storage at 40oF (4oC) was 3.4" thick batte. At lower temperatures -- 0oF (-17oC) or -10oF (-23oC) -- 5" and 6" thick batte, respectively, were used. The disadvantage of this insulation was that it had to be cut to size to fit the given cavity. This could result in a path for vapor migration if the batte was cut incorrectly. In addition, insulation by itself -- without a properly applied vapor barrier -- resulted in moisture buildup and degradation of the insulation and its physical properties.

If water vapor passes the vapor barrier, Erickson explained, a whole series of events begin to take place, all of which are highly detrimental to the refrigerated enclosure and its operation. For example, during warm and humid weather with accompanying high dewpoint temperatures, water vapor migrating through the insulation will be chilled to its dewpoint somewhere in the insulation and will condense to water. In the case of a cooler, the insulation will remain wet; in a freezer, ice will form. In both cases, the value of the insulation will gradually decrease until it is finally destroyed.

Today, refrigerated enclosure manufacturers used foamed-in-place insulation, which has an R-value of 7.1, or a U-factor of 31 for a 4" panel. However, Erickson notes that in today's markets, environmental green factor concerns are changing and demanding more environmentally friendly blowing agents such as 134a, water, propane and soybeans.