Our a/c maintenance man, who I like very much because he always compliments my housekeeping judging by how little dust is in our filters (this actually has far more to do with having wood floors and very few ‘dust traps’ as far as our furniture goes, but I am pleased to know that running a dust mop around irregularly is in God’s goodness, an effective means of dealing with this world’s dirt) came to repair a problem we had with our air conditioning last evening. After what felt like a thirty minute earthquake (mysterious in origin and explanation, as no one else seemed to experience it) our a/c started leaking water all over the floor yesterday. In the process of fixing this problem, whatever it was (my theory was a dislocated pipe from the extremely local but violent tremors) he explained to me the theory of air conditioning. I am a housewife of very unscientific brain, and I didn’t get it all. Nevertheless I found what I did understand extremely fascinating and quite useful.

1. At boiling point, water is both water and steam; and freezing point both water and ice. To overcome the surface tension of water at boiling point requires more energy than simply changing ice to steam (and vice versa). Somehow this ties into why the hardest thing the a/c is dealing with is not actually heat but humidity. (I found it incredibly wonderful as a mere fact, regardless of its relation to the a/c and humidity. Just imagine how much energy goes into raising water a tiny fraction of a degree next time you see steam coming out of your teapot. What a magnificent world, spinning in all this incredible strength that can just toss off enough steam for all the tea drinkers of the world daily. But I digress.)

2. Because of the humidity factor, and because your a/c is not simply cooling air which itself has very little ‘density’ (yes that is a word I quote verbatim) but is lowering the temperature of all the solid material in your home (including insulation), the a/c has to work much harder to effect a change in temperature than to keep temperature at a relatively stable degreeage (yes that is a word I just made up). It does *not* actually save you money to turn the a/c off during the day, to open windows (this lets in air that is of a different water saturation, not just a different temp), only to turn it on again when you get home in the evening and so on. The changing of temperature of solid material would also apply to a heater; and the water consideration would also apply, if I understand correctly, to at least some gas heaters (or heaters that use gas in some way — this part was a little beyond me: but water and steam are involved in there somewhere).

3. Not only does it make a great deal of work for the a/c, heat, and so on to wildly fluctuate the temp, without saving money — it can cause more mold than if you just always left the windows open, or always ran the heat/air. Because again, the heat/air are doing something with sudden large amounts of water when you suddenly kick them on.

The moral of the story is, that It would be better to turn the air or heat up or down in a not too drastic manner, and at least so far as the a/c is concerned, be careful about letting humidity into your home on a regular basis if you want to save $$ on the electricity bill.