It is, therefore, possible to calculate the impact of convection on R-value using published technical information. A test method for measuring the effect of free convection on thermal resistance is set forth in a newly-adopted standard, ASTM C 1373. This test should be reasonably priced and will confirm the calculated ARI-value. The higher the ARI-value, the greater the resistance to air movement. The chart shows the R-value of this insulation.
R means resistance to heat flow.
The higher the R-value, the greater the insulating power. Compare insulation R-values before you buy. The higher the ARI-value the greater the resistance to air movement. ARI is an indicator of how well the insulation will maintain its stated R-value under cold conditions. The higher the ARI the more insulating power the material will have under cold conditions.