NRCA: Roofing insulation performance, local climate keys to computing R-value

To minimize the loss of thermal resistance in design, the R-value of roof insulation should be computed based on the actual performance of the insulation material and the local climate, says the National Roofing Contractors Association. The long-term thermal resistance method of determination may generate an R-value required by the building code, but it does not take into account thermal resistance loss when metal fasteners are employed, according to a study. For the full report, click here.