Your shop looks great, well ventilated. We have been a little colder than you lately but my shop is not that open. It looks like you are useing a coal forge, I use gas and that heats my shop, even with ventilation. I am not sure how coal would do but if you just put canvas around the open areas above the pannels I would think that it would heat up enough to be pretty nice in there. I do use a fan to blow the air down from the cieling during the winter. I have it wired in with my lights for the winter. Then unplug it when it warms up. If you do not have lights use white canvas it lets lots of light in.

Great shop!

I wear lots of layers when working in the cold (we had -18c in the UK last winter!) My factory gets cold, then stays cold due ot the large lumps of metal in there.

I usually wear a sking 'base layer' , jeans , heavy cotton boiler suit, Tshirt, thick jumper and hat ! good quality thick socks make all the difference.

Ive just got a 'heated' bodywarmer for Christmas, that runs off re-chargable AA batteries. Ive not tried it out in anger yet as we are having a mild winter (so far!) it looks promising though.

You have it better than I do. All my stuff is tightlypacked in the garage, and I have to handtruck it all out into the drive way to do any work.
Ahhh- The fresh open air of the NY hillsides!
(Brrrr....)