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Insulation products with identical R-values can vary in performance

The different materials that are used in insulation products can have a profound impact upon their efficiency under different climate conditions. Experts say that two materials of the same R-value might result in varying performances. A recent article that appeared in Australia’s building news magazines explains why this is the case.

According to the article, the R-value for insulation products is based on the standard benchmark for a material's capacity to block heat transfer and maintain comfortable indoor temperatures efficiently. The higher the R-value of a given building product, the lower its thermal conductivity (k-value), and the better its insulation performance.

The use of a single value to determine the performance an insulating product can be misleading, simply because heat transfer occurs via a variety of mechanisms. This is why materials with similar R-values have variable performance depending upon the nature of the insulation.

Marc Howe, a writer for the Australian technology publication Sourceable, explains there are three mechanisms involved in heat transfer: conduction, convection and radiation. Conduction involves the transfer of internal energy by means of the collision of microscopic particles, convection is restricted to the collective movement of groups of molecules within liquids or gases and in radiation energy is transmitted or radiated in the form of waves or sub-atomic particles.

Due to the three-pronged nature of heat transfer, some parties split the R-value into two categories for building insulation - an "up" R-value that addresses upwards heat flow (referred to as "winter" R-values) and a "down" R-value, which addresses downwards heat flow (the "summer" R-values).

But even this further categorisation can not be relied on to adequately explain all the ins and outs of insulation, because it does not take into account the responses to ambient factors, and the impact that this can have on the efficiency of insulation materials.

Wall insulation products are, for instance, susceptible to phase changes, condensation or moisture buildup, which means they can all undergo significant variations in their R-value performance depending upon external temperatures. Another example is foam plastic insulation which contains blowing agents.

These foams can suffer sharp declines in their R-values as a result of shifts in ambient temperatures. The blowing agents can undergo phase changes because of their condensation and boiling points, affecting their resistance to heat transmission by means of conduction.

Ahead of buying insulation materials, it is imperative that you carry out extensive research that takes the various factors into account, as well as looking into the materials that have already been used.