Our gas company offers free home energy audits. I signed up. I learned a few things.
1. Air-sealing your second story is much more important than air-sealing your ground floor. When hot air escapes through your upper story it draws in cold air on the ground floor, so if you're not letting any air out then you're not drawing any air in.
2. Water heater insulation blankets are about to go extinct. They used to make sense, but all new water heaters have more than adequate insulation and there aren't very many of the older poorly insulated water heaters left anymore that can benefit from them.
3. Natural gas is so cheap right now that it has effectively halted the trend towards heat pumps in this area. In the long run it might make sense to have a dual-fuel system like that, but he thinks gas will be the better option for at least the next ten years.
4. As long as you have double-paned windows, don't ever replace them unless the glass is broken. He says the payback period on window upgrades is usually longer than your home's life expectancy. Even a 1/2 inch gap (3/4 is now standard) is so much better than single-pane windows that upgrading isn't worth it.
5. Blown-in attic insulation depth is now recommended to be 18 inches (about R-50) on new homes around here, but if you already have at least 12 inches (about R-36) then you won't notice any improvement by upgrading. He says it's really the first 6 inches that do most of the work, and the diminishing returns beyond that are pretty severe. The R scale makes it look linear, but the difference between R-1 and R-5 is huge while the difference between R-30 and R-40 is pretty minimal.
6. My house has a timer that controls a ventilation system for exchanging air. Mine was turned off. He recommends that everyone turn them off unless you have noticeable problems with indoor air quality, because otherwise you're just blowing out your heat and sucking in the cold.
Our house is ~2250 sqft and in January we used a new record high 2.4 therms per day of gas. In the summer we average about 0.4 therms per day on showers and dishes and such for a family of five, so I'm figuring that's 2 therms per day on heating during the coldest month of the year. We pay $1.00/therm for gas, or about $2/day in the winter and 40 cents per day in the summers.
MMM, by contrast, only uses 0.2 therms per day on showers and dishes for a his (smaller) family, and he only pays 62 cents per therm for his gas. But his new radiant heating uses a lot more gas than my furnace (or maybe it's just colder in Colorado than it is here) and so our total gas bills are about the same because he uses so much more heating gas than I do.
