If the coat is to keep you warm, make it a dark colour to absorb heat (radiation).
Ensure that it contains a lot of insulation (air in the fabric (as occurs naturally in wool) is good (conduction).
Convection is odd, it describes the motions in a medium (usually a gas or a fluid) of warmed particles. Not sure how that can relate to a coat.
I don't really know ... But I have a jacket for skiing that I bought at a Colombia brand outlet store that looks like it has tin foil on the inside and it cost me a small fortune and the sales guy sold me on it because it's for - some temperature and he he said it would keep me warm on the moon or something... So a coat that is shiny metal on the inside then ! I call it my astronaught jacket ! I have no idea what I'm on about now. My answer is tin foil and rooster you may delete this answer in the morning .. It's fine . 10 points.
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