A bit more about the value of going green. A friend in Santa Fe who's building her own straw bale house e-mailed me yesterday that replacing the windows in their old house with newer, more efficient models reduced last winter's heating bill in half – literally. And that's not just money they saved, but energy they would have otherwise consumed and carbon dioxide they would have otherwise released into the atmosphere.

Cost-benefit calculations are often considered in financial terms – how much money will I save by doing this instead of this – but where we're headed now requires an expanded, more complex view, one that includes environmental terms. If we junk our windows, we'll save money on our heating bills, but the old windows will end up in the landfill, and the cost of getting new windows will include the CO2 and sulfur dioxide emitted in manufacturing and shipping them, and the volatile organic compounds off-gassing from the stain of the windows' frames. On the other hand, we'll be saving natural gas and creating less air pollution over time. Like I said, more complex.

The windows in our place are, for the most part, pretty solid – efficient, double-pane deals. (The framing around them leaks like hell, but that's a different issue.) So we're not replacing them anytime soon. But we recently had a similar dilemma: Did we need to replace our dishwasher? Not really; not in the traditional sense. Though it was built in 1974, our old dishwasher still "worked." Meaning you could put dishes in it, and it would start up. But it never quite handled the "wash" half of "dishwasher" very well: Dishes came out, more often than not, in need of a further scrubbing. You know what I'm talking about – that last, crusted corn flake stuck to a bowl; the dreaded soapy residue on every water glass. (I wish I had taken a picture before we dumped our old machine. It was missing a few of its punch-button teeth – Rinse Hold and Heated Dry, I think – making it look like a mildly retarded cartoon character: Klanky the Totally Useless Dishwasher.)

Using the machine was never the default decision. As a two-person household, we rarely have a full load of dishes to wash anyway, so we usually would wash them by hand: tap on, water running, scrub scrub. If we had a dinner party, we might load up the dishwasher, but only after rinsing dishes in the sink first, and then run a full cycle on the washer, which, being a hundred years old, was about as efficient as a fire hose. Needless to say, we were wasting lakefuls of water with either method, which in the dry dry West is pretty much a mortal sin. And in that broader, water-sensitive sense of "need" – yeah, we needed a new one. Either that, or move to totally biodegradable dishes and utensils made of bamboo.

NEXT TIME: We find a new machine.