TPO
TPO is a single-ply white membrane rolled out in wide sheets. Seams are welded with hot air, which fuses the sheets into one piece. It's reflective, clean-looking and common on both homes and commercial buildings.
- Seams are welded, not glued
- Bright white surface reflects heat
- Usually installed over insulation board, which can include tapered slope
Modified bitumen
Modified bitumen is a heavy asphalt-based sheet, often in two layers, either torched, self-adhered or set in adhesive. It's tough, handles foot traffic and works well around parapets and penetrations. A reflective cap sheet or coating helps with the sun.
Which one?
| TPO | Modified bitumen | Foam | |
|---|---|---|---|
| Seams | Welded | Lapped | None |
| Insulation | From board underneath | From board underneath | Built in |
| Upkeep | Inspect seams | Inspect laps, recoat if coated | Recoat periodically |
See foam vs TPO.
Roofing questions
Is TPO good in New Mexico sun?
Its white surface reflects sunlight well. Quality of installation, especially the welds, matters most.
Can TPO go over foam?
Usually the old system is evaluated and removed or covered with a suitable board first.
Is torch-down safe?
It's done with care around parapets and wood; self-adhered versions avoid open flame.