What is the R Value in foam?
R value is a number that supposed to indicate a materials ability to resist heat loss. It is derived by taking the “k” value of a product and dividing into the #1. The k value is the actual measurement of heat transferred through a specific material. The test used to produce the”K” value is an ASTM test. The ASTM test was designed by a committee to give us a measurement value that they thought would be meaningful. This test was only designed for fibre insulations-fibreglass, rock wool and cellulose fibre. This test did not take into account air movement (which every building has) and moisture content. Water vapor is constantly moving back and forth through the walls and ceilings either from showers, cooking, atmosphere etc. Even small amounts of moisture will cause a dramatic drop in a fibres insulations R value by as much as 50%. Fibreglass is generally assigned an R value of approximately 3.5. It will only achieve this if there is zero air movement and zero moisture content. The aver
