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Natural Air Conditioning

Natural Air Conditioning

Hi there!

The “mid-summer lull” here in central Italy is day-in day-out full sun – no clouds – with temperatures of 33-37°C (that’s low-to-high 90′s for you ‘Mericans). We don’t have air conditioning, so what’s our green solution? What we call “natural air conditioning,” which means we keep the house open all night, close it up all day and our big stone house stays at a maximum of 25°C (77°F) during the day, which is a comfortable difference of around 10°C (18°F) between inside and out. What makes that possible for us is that the night-time temperatures typically drop down to between 15 and 20°C (60-68°F). Obviously, if the night-time temperatures stayed much warmer, it would be a lot less comfortable during the day.

We also have a generally dry climate (at least during the summer), and that means that wîth our “natural air conditioning” we don’t suffer from the “green walls syndrome” that happens to closed-up houses in places like Houston during the summer. Our relative humidity inside is about 50-60 percent – a long way away from the horrible 90-100 percent in the hot and humid summer climates.

When I was young (yes, Virginia, that was a LONG time ago!), one of our neighbours had what my father called a “swamp cooler”. That was an air circulation system through the house (I think it used the same ducting as the hot air heating for the winter, but running in the opposite direction), with an air cooler outside the house that cooled the incoming ambient air by evaporating water into it (water was trickled down over a treated wood lattice, like in a commercial water cooling tower). The warmer and humid air from the house was exhausted above the roof. This was in central North Carolina, and I guess the air was dry enough that the house wasn’t subject to the fungus problems that you would expect if it were more humid. I’m not sure, because I was never invited inside the house! The “swamp” part was that almost everything you could imagine grew in the water collecting pool underneath the cooling tower!

Another relatively primitive system involves running water over the roof of a house or other building. This had a water distribution system so that the entire roof was kept wet. Wow, scientific! Today, that’s not so smart, considering the water supply problems that are starting to crop up everywhere around the world.

A “truely green” solution is to use your solar thermal and/or photovoltaic panels to shade your roof. Ideally there should be a small air gap between the bottom of the panels and the roof – 1-2 inches. That will help with the insulation effect (air is a good insulator). This should work almost everywhere and will keep your house noticably cooler, even if you have good insulation in the space under the roof. Naturally, there is always an exception, and we are it! Here in Umbria, our equivalent to a regional planning board will not permit the view of our historic and beautiful countryside, including our beautiful clay tile roofs, to be disturbed by solar panels of any kind. In addition, and presumably for the same reasons, the view may not be disturbed by even relatively small wind turbines. Plus one for beauty, minus one for efficiency.

All the best, and ciao for now,

Craig
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