A trench raincoat is a long, water resistant coat with a belted waist, a storm flap across the chest and a collar that turns up against the wind. Duck Apparel sells trench raincoats in South Africa for the wet months, when the job is staying dry on the walk between a car, a station and an office rather than surviving deep cold. The collection covers The Regent Trench and The Landmark Trench, two coats built on the same idea in different proportions. A trench is the coat to reach for when rain is the problem and heavy insulation would leave you too warm.
A trench raincoat is a shell garment, so it works by keeping water and wind out rather than by trapping body heat. The insulated side of the Duck Apparel range uses duck down to hold warmth, while a trench relies on a tightly woven outer fabric and a construction that sheds water off the shoulders and down the back. The two serve different purposes rather than competing with each other. A trench is the shell layer for wet weather, which is what a Cape Town winter delivers between June and August as rain driven by wind, while a puffer is the insulating layer, which is what a Highveld winter asks for when the cold arrives dry. Many people combine the two depending on conditions. The other rain focused pieces sit in the wet weather collection, which is worth comparing if you want a shorter or more technical rain layer instead of a full length coat.
The second difference is how the two behave over time. A trench is designed to be worn open, belted or buttoned, so it doubles as a smart coat over office clothes. A puffer has one job and looks like it. If you commute in a city in South Africa and want one coat that works over a suit and over jeans, the trench is the more flexible of the two.
A trench raincoat earns its keep in two separate rainy seasons in South Africa. The Western Cape gets its rain in winter, from roughly May to August, so a trench is a winter coat in Cape Town. Gauteng and KwaZulu Natal get theirs in summer, from about November to February, when heavy afternoon thunderstorms arrive without much warning and an insulated coat would be unbearable in the humidity. A trench covers both because it is a shell. In the shoulder months of March, April and September a trench also works as a windbreak on days when it never actually rains.