Greening Your Air Conditioning

By Carl Seville, Networx

Feeling comfortable in hot weather requires two things to happen together: The temperature and the relative humidity (RH) of the air must both be low enough to keep you from sweating. The lower the RH, the higher the temperature can be for you to feel comfortable. Think about dry heat in places, like Arizona, where 80 degrees can feel pretty comfortable, while that same temperature in Florida can be oppressive.† Thatís because the RH in Arizona is probably about 20 percent while in Florida itís more like 90 percent.† Lower the RH and you feel cooler right away.

There are two types of A/C: traditional, which removes moisture from the air, and evaporative cooling, used only in dry climates, which adds moisture while cooling. For the sake of this post, Iím only going to consider traditional A/C in humid climates, so if you live somewhere really dry, you can go enjoy planting your xeriscape garden (sniff) and leave us Southerners to discuss how to reduce the costs and environmental impacts of air conditioning in Orlando, Atlanta and other sweaty locales.

First, dress for the weather. If itís hot, dress lightly and keep the A/C set a little higher.

Second, turn on a fan. Air moving on your skin makes you feel cooler. But donít leave the fan running all day ó only keep it on when youíre sitting under it. Really, Iím not kidding, it only works if the air blows on your skin. When it doesnít, the fan only adds heat to the room from the energy in the motor.

Third, control the humidity. The best way to do this is by sealing up the air leaks in your house, but that can be a big project for an HVAC contractor or roofer, although there are some DIY solutions. Even if you do a good job air sealing, you will still need to remove humidity somehow. If it isnít too hot, you might try using a stand alone or central dehumidifier. If you can get the RH below 50 percent, you can keep the temperature higher and still feel comfortable. If the RH is very high, then the temperature has to be much lower to feel comfortable. When your A/C runs it does two things: first it cools, and then it dehumidifies. If the A/C system is too big, it cools quickly and shuts off before it has a chance to take moisture out of the air. Smaller A/C systems usually work better than bigger ones because they run longer, which dries the air more.

Next, open the windows and doors when itís cool at night or in the morning. Then, before it gets too hot, close them all up, usually around mid-day or early afternoon. The house will stay cool, for a while – how long depends on how well-insulated and air-sealed the house is. When it gets too hot, turn on the A/C for a while, then, if it cools off enough after the sun goes down, open the windows and doors again and let the outside air cool off the house.

One last thing: sun shining in windows can really heat the place up. Close blinds on your south, east, and west windows to cut down on extra heat, or, better yet, install exterior shades or shade screens to cut out the heat before it even gets inside the house. When you dress lighter, open your windows, and use fans properly, you can use a lot less A/C without sacrificing comfort.

Carl Seville writes for Networx. Get home & garden advice like this on Networx.

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Wright J.
Wright J.2 years ago

Remarkable stuff in the blog I love the topic as well thanks. hvac Sierra Vista

Terry V.
Terry V4 years ago


Fran F.

Thanks for the tips. I wish we could install an attic fan, but what used to be our attic is now a bedroom. I'll look into whether or not a ceiling fan would be a good option for this space.

Ela V.
Ela V5 years ago

great advice

ii q.
g d c5 years ago


Sonny Honrado
Sonny Honrado5 years ago


Steve Gomer
Steve Gomer5 years ago

this was not a bad post, but it did leave out 1 crucial part. Your attic will heat up first, then as it becomes over heated, it will push that heat back down into the house. The most effecient way to cool the house is with an attic fan to pull the heat from the attic.. use this late in the evening, when temps are cooler,leaving windows slightly open to pull cooler air in. Once cooled, the attic will take half the day to reheat. so you can get away with no air conditioner for at least half the day!!!!!

Steve Gomer
Steve Gomer5 years ago

pretty good post, but lacks one crucial point. Your attic will heat up first, as heat rises. Once the attic is over heated, it will push the excess heat back down into the house. The most efficient way to cool the home is to use an attic fan(later in the evening) With windows slightly open to pull in the cooler nighttime air!! Once the attic is cooled, it will take hours to reheat, so you can go half the day with no air conditioner and still feel comfortable....

Steve Gomer
Steve Gomer5 years ago

this was a pretty good post, but lacks 1 crucial point. Heat rises. It will heat up your attic area first, then as the attic becomes over heated,the excess heat is then pushed back down into the house. So to effectively cool your home, install an attic fan to suck out the heat. Run this for a couple hours at night time(with windows slightly open) it will suck in cooler nighttime air.Once this attic is cool, it will take hours to heat up again, so the home stays cooler,longer,so you can get away with no air conditioner during the first half of the day.

Mary B.
Mary B5 years ago

I've lived in both Arizona and Florida, and now make my home in Wisc. Summers here lately have been hot and humid. I don't have AC so rely on shading the west windows to cut out radient heat and since I have lots of house plants, I find if I don't water them much, they will naturally take a lot of moisture out of the air. Fans help and a room with a high ceiling where the heat can accumulate also seems to work well if you don't turn a fan on in there and start mixing the lower, cooler air with the upper hot air. Opening every thing up as soon as the evening air cools to less than the inside temp, then turning on the fans for awhile to blow it out works quite well, but I always shut the east end windows first thing in the morning.My house is partially earth bermed and has a lot of thermal mass bult in so radient heat moves into that instead of just making the air hot.