Question: Montgomery county , Maryland requires that the ventless gas logs be vented 1/2 inch? Given this fact would it be a waste of time to install a ventless log system in my below ground level masonry fireplace. Would this actually produce any heat with this much of a venting? I have a woodburning fireplace insert there now but my wife wants me to convert it to gas logs. We like the Temco. Answer: Larry You will still get a bunch of heat with the damper open 1/2 inch... If you really want a lot of heat- you can install a gas insert - and vent it up the chimney with a 4" liner--costs more but a more elegant long term solution.