Fiberglass R-38 value Insulation installed in new loft style home under construction Tucson Arizona. The R value is the density and thickness and insulation value given to different types of insulating products R-38 is one of the thickest in the southwest and take up at least 12 inches of space. This image shows the TJI roofing trusses with Velux Opening skylight opening before drywall has been installed.
