We have had our insert for 2 or 3 years now and it never fails, when the temp drops below 30F or 40F outside we can't maintain an internal temp of 70F inside. We have a rather open floor plan and the actual thermostat to the main living area is no more that 15' away from the stove. We have even started cleaning our stove on a weekly basis hoping that would help and a deep cleaning at that, and that doesn't seem to help. Right now we are running the pellet stove and the heat pump just to maintain the home at 70F. Any suggestions?