Heat Loss By Convection, Conduction, and Radiation
Posted Under: Ask The Expert,Energy Savings,insulation
R-value is measured under laboratory conditions, but in the real world there are other factors that determine how effective a particular type of insulation may or may not be. Conduction, convection, and radiation all affect heat loss, but R-value only measures the first one, conduction, which is when heat is lost through solid materials.
Radiation is when energy emits from a source and “radiates” elsewhere. Radiative heat transfer is minimized by spray foam insulation. Radiation is also minimized by highly reflective surfaces such as spray foam, but because most insulation occurs internally to walls, this is less a factor than conduction and convection.
R-value does not take into account air movement, or convection. In a landmark study performed by Richard S Duncan and Roger Morrison with the Spray Polyurethane Foam Alliance and the American Chemistry Council determined that SPF walls exhibit nearly 10 times less air leakage than walls insulated with fiberglass insulation under a simulated 15 MPH wind load.
In summary, spray foam is one of the best performing insulators available today using any and all of the above measurements.
