I live in northern NJ and my house was built in 1998 and I'm the second owner. My heating system is gas fired hot water baseboard with a Utica boiler which I am guessing a builder's unit.
My wife and I are comfortable at 70 degrees and the house/heating system has no trouble except when the polar vortex shows up. During the overnight hours (no sun to help things out) my house struggles to maintain 70....we wake up to 65 degrees and a heating system that is running 24/7. I do not believe there is air in the lines since we installed a Spirovent air separator on the system....though I admit, the baseboard doesn't feel as hot as I "think" it should....but that could be my own expectation since they always feel hotter when its 30 degrees out versus 2 degrees.
My HVAC guy tells me that my boiler is putting out 180 degree water and its simply due to NJ building code is designed for 15 degree nights not the zero degree nights we have experienced the past 2 winters.
So.....where do I start?? Adding insulation? upgrading heating system? Or should I invest in a home energy audit?? Are those really worth it or do they simply try and sell you stuff you may not really need??