1. Use awnings.

According to the Washington Post, The Department of Energy estimates that awnings can reduce solar heat gain—the amount temperature rises because of sunshine—by as much as 65 percent on windows with southern exposures and 77 percent on those with western exposures. Your furniture will last longer, too.

We noted in Planet Green last spring that this can translate into a saving of cooling energy of 26 percent in hot climates, and 33 percent in more temperate climates where it might even make air conditioning unneccessary.

2. Plant A Tree.

I don't own an air conditioner. The house immediately to the south does it for us, completely shading the south side of our house. What it misses, a huge ancient maple in its front yard gets, so in winter I get a lot of sun in my window, and in summer I am always in shade. A tree is as sophisticated as any electronic device around; it lets the sun through in winter and grows leaves in summer to block it.

Geoffrey Donovan studied it in Sacramento, and calculated the savings.

"Everyone knows that shade trees cool a house. No one is going to get a Nobel Prize for that conclusion," says the study co-author, Geoffrey Donovan. "But this study gets at the details: Where should a tree be placed to get the most benefits? And how exactly do shade trees impact our carbon footprint?"

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