Walls are supposed to be R19 and the ceiling R30, but I haven't confirmed. I do have some air leaks and I've been trying to get them under control. This weather is killing me... Every time I get caught up with work and have time to go to the house it's snowing and I fall behind on work... I live an hour away.
There are some stupid things, like an open shelf in the wall that's the stairwell to the basement, so the insulation on the floor is useless. There was a wood stove in the basement that's been removed leaving an open hole in the wall which I just sealed temporarily and the walkout basement doors had a 1" gap under them. Also the windows aren't sealed either...
The unit hasn't been serviced since installed 12 years ago and when I got there the strainer was plugged solid. I replaced the nozzle and strainer but have yet to get a combustion analyzer on it. I also have to add a filter in the line from the tank... So there may be improvements to be had in the efficiency, but it's listed as an 80% furnace. Nozzle a 0.50 running at 150psi (It's a Beckett AFII 85 burner).
The ductwork is horrible and the house heats very unevenly, so the unit has to run much longer to warm it up. From when I fixed the heater I didn't check back on it for 9 days. We had a power outage for 2 days, so there was 7 days running with two days of having to heat the house back up. Going by the gauge I used about 35 gallons. So not the best for anything but a ballpark estimate and as I said I think the thermostat is off. It's one of the old round mercury switch types. When set to 60f it feels much warmer.
Oh, and I should also mention this was at a time when the weather here had highs in the mid 20's, lows in the single digits... Polar vortex and all...
Based on my back of the napkin calculations for 5 gal/day at 80% efficient I'm at 22-23k btu/hr heat loss... Not bad considering how cold it was outside.