Is the REBAR vest warm enough on its own?

It is a mid-layer. The fleece lining and softshell shell cut wind and hold core warmth, but in cold weather most wearers pair it with a long-sleeve base or a jacket over it.

No. The nylon softshell and canvas face resist wind and light moisture, but the vest is not a rain shell and seams are not sealed.

Does it have EN certification?

No. The vest carries no EN standard, so it is general workwear and not certified protective clothing.

How does it compare with a softshell jacket?

It offers the same shell and fleece warmth without sleeves, so your arms stay free and it layers more easily. A jacket gives more coverage in cold or wet weather.

What should I wear under it?

A long-sleeve work shirt or light hoodie suits it. The fleece lining sits against a base layer, so a smooth fabric underneath is more comfortable than a rough one.