Have a large stone fireplace with custom glass doors that are very air tight. Have an ash dump that goes to the outside. Trying to decide if I can use gas logs, close and seal the glass doors so as not to loose inside air, get my air from the ash dump and vent up the chimney. This would be much less expensive than a self contained gas insert. What problems would I encounter?
Your ash dump probably won't provide enough oxygen for combustion. Have you given any thought to a set of vent-free gas logs for your fireplace? They will allow you to close your damper and open the doors so you can get all the heat into your house.