Noel realized this afternoon that our furnace wasn't actually heating. He realized this when he looked at the thermostat and it read 60 degrees.
The heat-n-air guys have been here, and diagnosed a broken ignition unit. Because our furnace is ancient, they couldn't come up with one today, so they'll be back tomorrow morning to fix it.
The funny thing is that I think the heat has actually been off for a couple of days. Yesterday I was passing the furnace enclosure and felt a cold spot on the carpet. I stopped and felt around, and realized that cold air was blasting out of the vent. Now because what I was worried about was leakage (we've had plenty of leaks from that enclosure, related to the condensation outlet), and my feeling-around confirmed that the carpet was dry, I actually didn't give that cold air much thought. "Hm, maybe cold air comes out here, but hot air comes out of the ceiling vents!" I surmised with absolutely no reason, and went on my merry way.
Of course, now that I know the heat is off, the house does feel chilly, whereas yesterday it felt normal. But in at least 24 hours (maybe more) of no heat, the temperature in here has only dropped five or six degrees. (I credit the replacement windows we got a couple of years ago -- can't even imagine how quickly the house would be turned into an icicle with the drafty numbers that were here before.) And these are some of the coldest days we've had -- the temperature outside when we woke up this morning was 13. So if we've held onto the heat this well so far, we probably won't drop down below 50 tonight, I'm hoping.
Meanwhile, I fired up the gas logs for the first time in a couple of years, and at least the living room is snug. We've got plenty of comforters to pile up on the kids' beds. But I hope our no-heat adventure ends with a whimper tomorrow morning.