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Myths and facts surrounding long term ageing of foam insulation
von John Murphy
Many factors influence the thermal efficiency (lambda value or k-factor) one obtains with foams blown with any of the commercial physical blowing agents. Factors affecting a product’s thermal efficiency depend on, but are not limited to, the blowing agent itself – such as the blowing agent’s molecular weight, its boiling point, and its solubility in the foam matrix. Other factors depend on formulation parameters such as catalyst levels which affect speed of reaction and fineness of cell structure. Yet others depend on the mixing efficiency of the equipment used to process the foams.
Finally, a great deal of the contribution depends on the amount of protection the foam receives from its immediate environment - ranging from exposed foam to foam enclosed within impermeable facers.
The long term ageing of foams has always been filled with myth and controversy. This has been true for every blowing agent that has been commercialised. We will try to dispel some of the myth with the results of several long term ageing studies, run on ecomate and other commercial BAs.
In one study, the 5 year drift of insulation values was monitored by long term thermal value changes in comparison to unit efficiency over that span of time. This comparison pits ecomate blown foams against those made with R-134a.