Yes, I'm a homeowner, but I'm also a licensed electrician so I understand that you don't want to give away advice and info that someone else in your trade may charge for.
I have a house in the San Francisco Bay Area that my Dad built in around 1978. It's somewhere around 2000 sq ft, and has two levels separated by a wide open staircase. Living room, family room, and kitchen on main floor, three bedrooms and two bathrooms on the second floor. the entire main floor has exposed beam high ceilings with an almost entire wall of windows. There are also skylights, and some windows that are single pane.
I'm trying to invest in my future and make the house more energy efficient and also be more comfortable keeping the temperature comfortable without feeling like my heat is all escaping. So, I've been installing dual pane windows when I can afford it, putting plexiglass on the ceiling over the skylights to artificially dual-pane them. Overall the house is well-built and well-insulated, but at the same time it does seem to lose heat quickly so I'm just not comfortable keeping the temperature comfortable, also because I rented out a couple of bedrooms and we split the bill, so they'll ***** about the utility bill if it gets too high. I'm sure it wouldn't be TOO much if I just set the thermostat at 68 and let it just do whatever it has to do, but I really feel like it will be cycling a lot. The other problem is that the thermostat is on the main floor, so I would also kind of imagine that the upstairs will get too hot before the leaky downstairs (high ceilings, single pane sliding glass door, single pane kitchen windows, etc.) gets warm enough for the thermostat to shut it down.
The ducts are all hard-pipe and wrapped with bare fiberglass insulation.
My Dad said that the furnace was over-sized (not good?). It's a 140,000 BTU Rheem RGAA-14BA that was installed at the time the house was built.
So, here are my questions. Before I ask, I would like to thank everyone for reading this and hopefully giving me advice! And, I know I have a lot of nerve joining this forum just to ask this question and in reality probably not able to give anything back to these fine folks. (I'll support the sponsors/advertisers though)
1. Does anyone have an idea of the approximate AFUE rating of this furnace? I know you won't be able to give me an exact #, but is there a rule of thumb like "over 100k BTU before 1980, probably around 75%" or something?
2. Does it seem oversized based on any general rule of thumbs?
3. This is a subjective question that depends on financial situation and so on, but do you think it makes sense to replace the furnace with a more efficient one?
4. What do you all think of these 2-stage furnaces? I've read a little about them and they seem neat, but you all are the experts.
Anyway, you can see where I'm going with this. I want to invest in my energy-efficient future and replacing the furnace at some point is going to be part of this...along with many other things...dual pane windows and skylights, weatherstripping for doors, compact fluorescents, etc.
THANK YOU ALL and MERRY CHRISTMAS!