TPO (Thermoplastic Polyolefin) has become the dominant commercial roofing membrane, surpassing EPDM and PVC in market share. 60 mil membrane is standard for commercial applications (45 mil for re-roofing, 80 mil for premium). Installation: mechanically attached or fully adhered over polyiso insulation. Heat-welded seams provide superior waterproofing versus adhesive seams. White surface reflects solar radiation — Energy Star and Cool Roof Rating Council certified. Can reduce cooling costs 10-30%. Compatible with polyiso, EPS, XPS, and mineral wool insulation boards. Wind uplift resistance: FM 1-90 to 1-195 depending on attachment. Manufacturers: Carlisle, Firestone, GAF, Johns Manville, Sika. Warranty: 20-year standard, 30-year available. Average installed cost includes membrane, insulation, and labor. Minimum slope: 1/4 inch per foot.