R value, or Thermal Resistance value, is a measure of an insulation’s ability to resist heat loss via conduction.
The higher the R value the better the resistance to conduction. R value provides one means of comparing different insulations. However, R value is measured in a laboratory under ideal conditions and does not necessarily reflect how an insulation system performs when installed in an actual building.
The is zero air movement in a laboratory R Value test whereas air movement is very common in actual buildings and has a dramatic effect on the performance of insulation.
Heat is lost via 3 mechanisms:
R Value measures resistance to loss via conduction only. However, the loss via convection (heat transfer by air moving from hot areas to cold areas) can be responsible for as much as 40% of heat loss in buildings. click to view report
NZ authorities recognize the importance of sealing the building envelope: “The effect of poor installation, e.g. folds, tucking in, and gaps as small as 2mm, can reduce the insulation value of the building element by as much as 50% because it allows air movement around the insulation. (NZ standard 4146:2006, page 15).
Sealection 500 eliminates loss due to air movement by expanding to fill all gaps and cracks providing an airtight seal. So before you talk about even 1 R of thermal resistance Sealection 500 has stopped up to 40% of heat loss.