What is TPO roofing?

How it differs from EPDM

EPDM is black synthetic rubber with bonded seams; TPO is a white thermoplastic with welded seams. The welding is the real distinction. A correctly welded seam fuses the two sheets into one, which is stronger than an adhesive joint and is the reason TPO can perform very well.

The reflectivity is the other. On a large unshaded roof over conditioned space, a white surface makes a measurable difference to cooling load in a Maryland summer. On a small shaded rear addition it is close to irrelevant, and EPDM is often the more sensible choice there.

Where it is the right call

Commercial and multi-family buildings with large exposed decks, where cooling load is a real operating cost. Row-home and low-slope residential roofs that get full sun. Anywhere the building owner values the reflectivity enough to pay for it.

Where it is less obviously right: heavily shaded roofs, very small areas where the reflectivity gains nothing, and roofs so cut up with penetrations that the seam count climbs and the installer's skill becomes the dominant variable.

The thing to actually ask about

Not the brand. Quality does vary between manufacturers more than it does with EPDM, but the bigger variable by far is whether the welds were done properly — correct temperature, correct speed, and checked rather than assumed.

So the useful questions are about the installer: how the seams are welded, whether they are probed or tested afterwards, and how the terminations and penetrations are detailed. A cheap TPO roof is almost always cheap because of what happened at the seams.