Hello Rowdy. The OAK and vent are not installed in a masonary flue. We have 4 inch pipe. I have been playing around with the thermostat, but typically run it in manual mode with +2 flame height. Depending on the outside temperature, I set the heat output on medium, medium high, or high. I have the thermostat programmed to 64 degrees when we are not home and 74 degrees when we are home. Heat output is on medium low overnight and when we are not home. When I want heat in a hurry a put the heat output on high and flame height at +3. Like I said, still playing around with things. 36 degrees and windy here today and the house is 73 degrees.