I live in the mid-Atlantic in a 100 year old house, and I'm looking for a way to reduce my heating bill. Last winter, I left the thermostat at 68F, and our gas bills were incredibly high, despite still feeling cold inside the entire time. I received an energy audit, but, except for confirming the fact that we have no insulation in the walls, it was pretty worthless. All of their recommendations came out to cost about $25k (after government rebates) and they calculated that it wouldn't pay for itself for 47 years. Needless to say, I decided to not use their services.
This winter, I hope to make at least one serious improvement to the house to help out with heating efficiency. Some of my ideas are listed below. I am wondering which will get me the most bang for my buck, or if there are other potential projects which I haven't thought of.
Add Wall Insulation
The house doesn't have any insulation in the walls. The plan would be to tear down the walls in select rooms and add fiberglass batt insulation, then put drywall back up. I am hesitant to use foam insulation mainly because I plan on redoing some of the electrical wiring, and I feel like using foam insulation would wake that very difficult. Plus, when I take the walls down, I can run electrical lines at the same time as adding the insulation. Taking down the walls and installing the insulation would probably be a DIY job, but I might hire someone to do the drywall.
I have already replaced the old modly, compacted insulation in the attic with 6" fiberglass between the ceiling joists, but I could probably add more too.
We have a gas boiler that heats water (not steam) for cast iron radiators in each room, but it looks pretty old. The "Energy Guide" sticker on the furnace says the efficiency is 83.5%. I know that some more modern hot water boilers have efficiency ratings as high as 95%, so another idea would be to replace the boiler with a new efficient boiler. I would have to high someone to install the boiler - at least the gas lines.
Replace the Windows
All of the windows in the house are original, so there is a lot of heat escaping through the windows. Since replacing windows in the entire house is a pretty large undertaking, I would probably just figure out which are the worst offenders and replace them. This would also be a pro job.
Which of these would give me the most bang for my buck for reducing my heating bill? Is there anything else I missed?