Maybe if you could get a sheet of plexiglass to cover the open side and drill holes in it for the winter that might help with temp control but still ventilate because ventilation is important especially in the winter actually, but I'm just a newbie so don't take my word for it. I haven't kept exact records because it would shock me but I'm pretty sure I've spent about 500 dollars with using recycled materials but it's a startup cost I don't regret because I'll get that money back eventually through the eggs they'll produce for me..
