Do ground blinds hold in heat? from breath and body heat and stuff? If it does, i won't even need a heater. Plus, the black interior will absorb the suns heat too and heat the inside.

Opinions?

Ground blinds are nice in winter primarily to protect from wind and rain. Depending on how cold it is outside you may not need a heater. Remember you have sight openings that allow heat to escape. Actually, all it is is a tent with more holes. If you can sleep in a tent with the clothes you hunt in you should not need a heater. If not you can use something like a buddy heater which is very light and portable.