The World’s Most Efficient Air-Conditioner

Well, I’m finally done building that fence I’ve been meaning to build for the last few years. It came out great, and now we at last have the nice, private yard that this house of ours deserves. But as with every do-it-yourself project, other unexpected benefits were revealed as well, and one of them was that I ended up with a free air conditioner of unsurpassed efficiency.

To get this fence built Mustache-style, I didn’t whip out my cell phone and credit card and call a fence contractor. I had to do it myself, and since it was my first large-scale fence (about 180 linear feet at 6 feet of height), I kept track of some of the stats.

I had to set 25 posts of treated lumber into the ground. The posts were each 8 feet long, weighing 30 pounds each and set into about 80 pounds of concrete. Of course, before setting each post I had to carefully line up and carve a 2-foot-deep hole in the rocky, dry Colorado hardpan soil. Each of those 80-pound piles of excavated soil and rocks was the result of several minutes of wrestling with a burly electric drill equipped with a 3″ soil auger (a very useful invention!) followed about 100 blows with a manual post-hole digger, and occasional attacks with a sawzall to cut through roots, a diamond blade grinder to cut through concrete, and a handheld jackhammer to chip away anything that remained. And all those holes were just to get me to the point of hand-mixing over 2000 pounds of concrete, manually tailoring, drilling and screwing over 100 cross pieces, and nailgunning in 500 cedar planks, cutting and bending each to coax their naturally-curvy demeanor into the extremely tight and straight fence that I wanted.

All in all, it was about 69 hours of work, and it was done through a period of record temperatures in my area. Some days topped out at over 100 degrees Fahrenheit (37C), and few were below 80. Half of the fence is in full sun, leaving me with only SPF 80 sunscreen and my sun hat for shelter.

But a strange thing happened as the days went on and the fence sections were completed, one after another. I stopped noticing the heat, and started feeling downright comfortable. The improvement was so dramatic that I thought it was the weather that was changing rather than me. Often I’d walk past my outdoor thermometer on the way to refill my water mug, and be shocked to see another mid-nineties reading, when I felt like it was under 80. And at the end of each day, I’d find myself inside the house feeling comfortable even with a shirt on, noticing an indoor thermometer reading above 85. In previous years, I had felt the need to turn on the air conditioner at around the 80 mark. Morning house temperatures in the high 60s suddenly felt bone-chilling to me, even though in the winter I normally curse the stuffy house and go outside to get some fresh air if someone turns the thermostat above 67.

What I had done with all this work in the heat is given myself the gift of Heat Acclimation. This is a form of Badassity that is not just something made up by the most spartan of Mustachians. It’s a real and scientifically measurable body adaptation – a gift of comfort that YOU should give yourself this summer, because the benefits are enormous.

To get some of this goodness for yourself, it helps to understand what it is.

When a normal office worker encounters unusual heat, his body tries to cool itself by sweating. The body also circulates heated blood out near the skin’s surface, allowing heat to radiate and convect through the skin and evaporating water. That’s why overheated people often appear more reddish in color.

The problem is that this leaves less blood in the core of the body where the muscles are working, and it requires a higher heart rate for any given volume of work. In short, you slow down at whatever you are doing, and if you push too hard you start feeling like shit and just want to lie down in the shade.

But when you’re out in the heat, your body is starting to wise up to the situation. It creates more blood, the endurance of your sweat glands increases, and the ability to sweat efficiently at the first sign of heat increases. You really do become a Badass Heat Survival machine, and research indicates that you’ll see significant results within just one week of spending an hour or so outside in the heat doing light exercise like walking or biking. I’d estimate that my own acclimation has sliced about 12 percieved degrees Fahrenheit off of this summer’s heat.

The more you do it, the better you get, as witnessed by the Phoenix-area MMM readers who insist that they can easily bike to work year-round in that hot desert city where daytime highs are rarely below 40C (104F) for months on end. This also explains the amazing abilities of my Mexican concrete subcontractors back in the house-building days. These guys would often work alongside me on searing-hot days in black jeans and long-sleeved Denver Broncos sweatshirts, while I could barely survive with a white t-shirt, dark sunglasses, and enormous straw sombrero.

In other words, when someone says, “You can’t spend time outside where I live, it’s TOO HOT!”, it’s really equivalent to saying, “You can’t bike to the grocery store where I live, IT’S FOUR MILES AWAY!” – it’s not a question of impossibility, just of acclimation.

But this post isn’t really about extreme heat survival, like those 120F Phoenix days. It’s about a much easier and more relaxing kind of heat acclimation – making the most out of your own climate in the summer months.

During the peak of the last hot season, I wrote a rant called “How Not To Use Your Air Conditioner“, where I railed on the excessive use of A/C by modern people. This year, I’m doing it again, but with the added perspective of this new experience of extreme heat acclimation, because it works better than I thought.

Here’s an interesting fact: because my house is fairly well insulated and captures a lot of winter sunlight, it acts as a significant buffer against weather changes. I’ve measured that even without a furnace and with no air conditioner, the temperature in here would never go below 40-50F in the winter, or above 86F in summer. In other words, if I were badass enough to put up with the full range of those temperatures, I could run with zero heating and cooling costs indefinitely. 100% of my costs (about $450 per year) are to fine-tune that temperature to allow my family a more luxurious lifestyle.

So as your wimpiness increases, so do your heating and cooling costs. At the extreme end of the spectrum, some people are such heat wimps that they cool their house to the meat-locker temperature of 72F in the heat of summer. You can spend $200 per month keeping a house that cold, even while the house’s natural temperature without cooling might be barely above 80.

Gaining heat acclimation in the summer (and cold acclimation in winter) is about more than just utility bills. It also opens the world back up to you, allowing you to get out and do things that you’d normally wimp out of doing.

A common lament across America these days is this one:

“I know Mr. Money Mustache taught me I have to get my groceries with a bike trailer, and I’ve been doing it all spring. But now it’s just so hot out there, and he doesn’t know where I live so he won’t see me… so I think I’m just going to sneak out and use my air conditioned car until the hot season ends”.

When Junior Mustaches pull stunts like that, they think they are fooling Mr. Money Mustache, but they are really just fooling themselves. Riding around in your climate-controlled car is just like taking another shot of heroin to prolong a lifetime habit. Instead, you can kick the addiction to comfort, go through the necessary downtime, and be free for life (see: Trainspotting).

So let’s just try this experiment: get yourself out in the heat for at least a few minutes every day. Not just walking to the car, but seriously out in the heat. Go for a walk, try a run if you’re a runner, bike to work, even go out fishing. Drink loads of water (during my fence work I went through about 4 32-ounce jugs of icy water every day). And eat a banana or two to help replace electrolytes lost through sweating.

Instead of increasing your suffering, you’ll actually be building your ability to stop suffering. Take it up to an hour a day. Increase your A/C temperature by one degree every day or two. Watch your need for air conditioning drop drastically. Watch your enjoyment of the outdoors increase. Watch your Money Mustache grow.

A cautionary statement, not that people like MMM readers need these things: heat CAN be dangerous. Your body does need to keep its core temperature within a certain range, otherwise bad things happen. As physical fitness decreases and age increases, so does the risk of overheating. That’s why when record heat waves strike, you always read about a bunch of elderly people kicking the bucket in their non-air-conditioned apartments.

On the other hand, if you carefully and gradually push your comfort boundaries, just as with any form of other exercise or badassity training, you tend to extend those boundaries in a positive way. I try to spend at least an hour a day doing something at least mildly uncomfortable. Just as I once suggested that we should all learn to appreciate mild hunger, it is also nice to appreciate mild discomfort. Without it, you are on the slippery slope to lifetime wimpiness, a place much worse than mild discomfort!

I can see it’s back up in the nineties outside there today. Full sun and no wind. It’s far too comfortable down here in my basement office, so I’m going out for a ride!

  • Allison June 16, 2012, 1:57 pm

    As someone who went without air conditioner through summers in VA, I always considered myself a “hot weather person”. Fast forward eight years and last year I found myself going without a coat in 30 degree weather while commenting on how nicely it had warmed up following a stretch of highs in the -20s. It’s amazing how easily the human body adapts. But, I never thought of purposefully forcing an adaptation. It’s a great idea!

  • barry iduhn June 16, 2012, 2:00 pm

    Wow how long did it take you to build the fence around the tree? A 2D projection of an irregular 3D shape like that — next time I need a carpenter I will try to find an ex-software engineer.

  • JZ June 17, 2012, 12:05 pm

    I’m a bit stumped on this one, myself.

    In New Orleans (not quite so hot as the desert climates, but high humidity), I regularly ride my bicycle an hour each way to get to campus, plus other sundry bicycle trips. These feel pretty tolerable. So does walking. But if I try doing other exercise outside or in an uncooled venue, the heat catches up to me very quickly, faster than the other people around me doing the same things. I’m not sure whether biking is just a poor way to be exposed to heat, or if there is something else going on.

  • Toni Murray June 18, 2012, 6:04 pm

    I will point out that although adults have an amazing ability to adapt to heat or cold, young children do not–it can be quite dangerous for them.

  • Concojones June 19, 2012, 3:51 pm

    When I moved South to NorCal last June, and stepped out of the air-conditioned car on arriving, the heat hit me in the face like a brick, sweat started pouring out of my every pore, and I remember wondering why anyone would want to live in NorCal.

    Within days the oppressive heat started to feel bearable, and a few weeks later I was happily doing 8-hour shifts of heavy lifting in the full mid-day July sun, and I remember enjoying what seemed like “nice and warm weather”.

  • Jackson June 19, 2012, 4:49 pm

    I love the heat. Public places and other people’s houses are almost always air conditioned too cold for me. As long as I have a sufficient supply of cold water with me, I love to exercise outside in 90+ heat.

  • Derek P. June 19, 2012, 8:19 pm

    This is totally in tune with us that work outdoors regularly. Depending on where you live some of us deal with some huge temperature ranges. Its a pain in the butt to get use to such a range of temperature (-52C to +56C is my 1 year record), but what doesn’t kill you makes you stronger eh?

    It also goes back to keeping yourself in good physical condition. People who are lean and a healthy adapt a lot quicker to the weather than the overweight and in poor health. Overweight people “love” the heat….

    My free entertainment daily here in Australia is the locals making fun of me wearing only a Tshirt while out in ‘freezing cold winter’. They are walking around in winter jackets in 15C weather when I wouldn’t put on until like -15C! I am Canadian!

  • The Clean Shave June 21, 2012, 4:27 am

    Sounds very recognizable.

    Spent last summer bicycling from Budapest, Hungary to Prague, Czech Republic. It gets scorching hot in continental central/eastern Europe, and we had 960km to cover.

    – First day: we arrived at noon in Budapest, fled into a shopping mall to escape the heat and barely made it out of the city and onto a camping.
    – Second day: we started early, stopped at a sleepy village along the Danube river, raided a mom’s and pop’s for food and unrolled the ultralight hammocks under a couple of massive trees to watch the town ferry go back and forth for a couple of hours. Gorgeous, but not doing much.
    – Third day: everything became business as usual. Cycling from 9am through 6pm in the heat on bicycles packed with camping gear and wildly varying elevation levels? Ninguna problema, hombre.

  • Anonymous June 22, 2012, 1:16 am

    You mentioned the idea of drawing in outside air at night, to take advantage of cooling. That works nicely if you consider your HVAC system primarily a means of regulating temperature.

    In our household, the HVAC system has as its primary function the filtering of air and removal of allergens, which everyone in our family has severe trouble with. Temperature remains a secondary concern. The HVAC system exists to keep the outside *outside*, and separated from *inside* by several layers of filtering. As a result, none of us need to take our allergy medications when staying inside, only when venturing outside during the ~12-month allergy season.

    Given that, we try to let in a minimum amount of outside air, at night or any other time. The temperature difference might improve efficiency, but at too high a cost in comfort. We’re well aware that we burn a significant amount of money doing this, and we consider it worth every last penny.

    Writing that out explicitly actually made me think of it in a way that I hadn’t previously, which makes me feel even better about it: I can easily measure the additional amount we’d spend on allergy medications if we had to take them every day rather than every time we go out. A quick estimate puts the additional cost at approximately $167/month just for *me*, not counting other members of the family. Averaging that over the course of the year, that would cover the entire electricity bill by itself with room to spare (not just the AC costs, and certainly not just the additional AC costs incurred by not making use of cool outdoor air at night).

    • Mr. Money Mustache June 22, 2012, 7:11 am

      Anonymous, while your comments are thoughtful, I think you might have a slight case of “complainypants” disease!

      If you’re allergic to the place you live, maybe it’s time to figure out where you can live that your body doesn’t fight constantly? Depending on man-made structures to protect yourself from nature should be a last resort rather than a preferred way of life (unusual chronic illnesses aside, of course). You might even find, like I have, that allergies disappear with health improvements (I used to be destroyed by summer allergies in my early 20s, and now haven’t had a plant made me sneeze for many years – no filters, no medicine!).

      • anonymous June 22, 2012, 5:31 pm

        (First, a correction: my quick estimate of allergy medication expenses if required daily actually overstates them by a factor of two; I misremembered the number of doses in one prescription. That changes the math enough to suggest that I should actually do the math to check my hypothesis.)

        I have a sufficiently broad spectrum of nature-based allergies that unless I want to live in a place mostly devoid of plant life, I’d still have problems anywhere I went; this area actually provides a significant improvement in that category compared to other areas of the country. And I love this area too much to trade it away for lower allergy-management expenses, even ignoring the advantages of this area from a career and cost-of-living point of view.

        We’ve already selected a region of the country with a fairly optimal balance of relatively low allergy problems (by comparison to other places we’ve lived) and quality of the area in the hundred other ways that we love.

        Look at it this way: you’ve chosen to spend extra on your home, as something you highly value. I’ve chosen to spend extra on my home in a slightly different way.

        I already have specific actions and goals to improve my overall health, and if that leads to a significant decrease my allergies, wonderful. If not, my allergy medications and air filtration will continue to fall firmly in “cold dead hands” territory, which in practice means that if I need to cut that amount from my spending I’ll find somewhere else to cut it.

        Also, I want to point out that I never allow allergies to provide an excuse for not doing things, least of all going out into the world; that would indeed make me a complainypants. I will not become a bubble-person; however, I enjoy spending time in my home, and thus I’ve optimized my home to support me more efficiently. “Put on slippers rather than carpeting the world” should not stop you from carpeting your home. Figuratively speaking; wood floors all the way. :)

        I only brought this up at all because your article assumed only a single use for HVAC systems, namely temperature control; I wanted to suggest an additional use that you might not have considered. Please don’t take that to imply that I allow allergies to become an excuse for me, rather than a simple obstacle that I have found many ways to overcome.

        • Mr. Money Mustache June 27, 2012, 3:41 pm

          Well said!

        • Dancedancekj July 5, 2012, 1:52 pm

          You might want to try a Paleo diet. I suffered for years from allergies (no medication or conventional therapy or alternative therapy would touch it) but I’ve experienced a lot of improvement in my seasonal allergies for about a year now since converting to a Paleo diet.

  • Monevator June 22, 2012, 12:29 pm

    Reading this here in the UK in London where it hasn’t stopped raining for six weeks and the temperature has barely got above 20 (erm, 70 fahrenheit?) this post is much more provocative than the financial ones… ;)

    I can tell you what in contrast the world’s best natural heating system is… an air flight to Spain! ;)

  • Spectator July 15, 2012, 2:05 pm

    Nice project.

    What the writer describes as “badassity” is otherwise known as outdoor work.

    Grandparents been there, did that.

    The article points are valid; if you’re in moderately good health then don’t let yourself become a prisoner of 24 hour climate control.

    And if you haven’t tried it, the bike idea is a real win. Even at a modest pace, the bike breeze effect cools you off, and bc you are outdoors and not stuck to a chair sweating isn’t unpleasant. Just wear stuff that feels good when you sweat, a headband to keep it out of your eyes, and a hat/helmet of some sort.

  • Mike August 4, 2012, 8:08 am

    Recently discovered the blog, and I love it. Prior to setting foot on the path to mustachianism, I bought a house 1700 ft.² brick, nice but radiates heat at night and I live in upstate New York so the humidity is almost like the sweltering jungle. That being said, the only room in which I have an air conditioner is my bedroom and I only turn it on to sleep. I can live with the heat during the day but it is almost impossible (for me) to sleep with the heat at night even with open windows and fans. I also went to Austin, Texas (holy crap, what an awesome town) this June and found myself gradually getting used to the heat as well but I think the big component there was a lack of humidity. If you live in a climate where there’s not a lot of humidity I think it’s a little easier to acclimatize yourself then it is with the crushing humidity in New York (and yes, I am being a little complainypants here, but hey, I’m a junior Mustachian, it doesn’t happen overnight, ha.)

  • FrontalNerdity September 9, 2012, 6:38 pm

    I’m also discovered this blog and would love to bad-ass my ways some more. I live in a 1100sqft 1.5 story wartime home in southern Ontario. Now I’m not going to convince the wife to go without AC in the dead of our humid-ass summers, however I use our poor-man’s AC when ever I can. I use the ‘stack effect’ of the house, where there’s a temperature gradient between the basement and upper level, I turn on the upstairs bathroom fan to exhaust the hot air while turning on the furnace blower to circulate the cool air from the basement.

    As for vehicle A/C, I never much cared for it and use it at little as possible. The one reader described been blown cool dry air mixed with the radiant heat from the glass was their less-preferred choice of discomfort. However I’m vetoed by the family on this one. I have some work to do.

  • Sister X October 18, 2012, 1:05 pm

    At the risk of copying other statements, YES! I get so sick of people in my area who complain about cold winters and wonder how I can walk to work even in the middle of winter. I have two things I say: one is that you get used to it, the other is that I actually dress for the conditions! So many people here expect to dress like they would at any other time of year with maybe some overclothes (hat, scarf, gloves, coat) and then complain that they’re cold. (I live in interior Alaska.) When someone complains about the cold I either point out that they could move, or that they could throw on some long underwear and stop whining.
    People lived here long before modern conveniences. I consider myself damn lucky that I get to walk from one heated building to another!

  • Green Girl Success June 22, 2014, 12:44 pm

    I know I’m late to the conversation here, but I love the concept of heat acclimation. I currently live in Arkansas and the summers are VERY hot and humid. I work from home and leave the A/C off all day. If I get uncomfortable, I just put a small fan near me. I don’t have a car, so I walk and bike everywhere. I purposely try to go running during the hottest part of the day for that acclimation. There is another benefit to dealing with the heat… appetite control! During these hot days, I find that I eat waaaay less and I crave mostly raw fruits and veggies.

  • Dr. $hevil December 22, 2014, 5:14 pm

    Damn straight. I’m very late to the party, having just discovered MMM. I’m reading through every single post in order.

    Air conditioning is a particular peeve of mine. My hubs and I refuse to turn on our window AC until the temp hits 95. And we’re in humid MN, which actually gets extremely hot for a few weeks in summer.

    I am working on training myself to withstand the cold of winter, as well, though I’m a mere slip of a girl without much natural padding.

    • Ann Curran December 23, 2014, 5:42 am

      Welcome Dr. $hevil! I too live in the frozen north and have little natural insulation. Two things help me tremendously in the cold months — not letting my skin get dried out, and wool underlayers. (I learned the importance of both of those firsthand from winter camping trips years ago.) In the fall I don’t shy away when the cold weather comes. I spend lots of time outside, and work as long as I can before putting gloves on. We keep the temperature turned down in the house — 67 in the day and 62 at night. The body adapts, and it makes winter so much more enjoyable.
      Good soft wool underwear tops and bottoms are a smart investment. You can wear it several times, as wool does not pick up odors like polypro or other synthetic materials. You wear, hang it up to air, and wear it again the next day. Eventually when it does start to smell you wash it in cold water and hang it to dry.
      I think MMM did a post a while back on underwear in winter — it is called something like “The Oil Well You Can Keep in Your Pants.”

  • Matt Vaudrey May 11, 2015, 1:05 pm

    We’re new to the Mustache business and are slowly chipping into waste and saving more, and I haven’t seen any references to this question, so I’m asking it.

    We have two kids (babies) and live in Southern California. Has anybody tried to acclimatize their young ones this way? How young is too young?

    And yes, we’re aware that we’re paying money to use the A/C and in exchange, are getting a good night’s sleep, not attending to crying, hot kids all night.

  • Purewishing June 19, 2015, 2:50 pm

    It would be helpful if folks could say where they are located when posting their A/C tips. I’m in northern VA and with the humidity, and mosquitos it gets pretty nasty here. I still work outdoors every chance I get, and we keep our A/C off for as long as possible, but if it gets over 85 with 80% humidity, it gets hard to get anything done.

  • Jen June 26, 2015, 7:41 pm

    Is there somewhere a post about instant water heaters? If anyone has a link please share. I have googled only find stuff from companies selling would like to see if anyone did an ROI on it. I grew up in Europe just seems to me instant water heater would make sense vs constantly heating a whole bunch of water that you don’t need at the moment. My heater is gas so is my stove and my bill is always around $20-$30 don’t know what % is water heater the expense is so low not sure it would make sense changing out unless broke. Just interested in seeing what people think. Thanks

  • Timothy Kukler December 11, 2015, 3:47 am

    This absolutely works. This year Sabrina and I didn’t even INSTALL any air conditioner in any room, opting for more iced-water instead and we employed the ceiling fan in living room. At night a simple fan in the bedroom did the trick for us.
    One’s body acclimates, for certain.

    It’s the first year (in our lives) we ever tried no-AC and I must say that I didn’t really notice after the first week. For us having a handy water bottle always on hand did the trick, this included working out in the sun one weekend working on a porch project, it was well over 95. It’s easy if we planned it, to have our lunch inside, enjoy talking and relax between 1-3pm, the two hottest hours of our day.

  • Stephanie June 14, 2016, 11:54 pm

    I really love most of your posts. But I am calling you a whiney complained pants on this one. Really, you needed an auger to dig some fence posts holes? I’m a lady and I’ve been digging them sans auger/drill here. Just with a post hole digger and a shovel. Doing it in Minnesota and did it in South Carolina. Completely different soils in each one.

    Again, you run your A/C? *pffft* If your house stays 80, just turn on a fan in the room that you are occupying. I’m in MN and we don’t run the A/C at all. It gets up in the 90s sometimes, but that’s what fans and water are for-keeping cool. Our house stays pretty cool, so we leave the windows open to get that nice midwestern breeze and sometimes use the fans. In the winter we close up the windows at night, sometimes if it’s still in the 40s or 50s we might open the windows for some fresh air. We turn on the heater at maybe 20-30 degrees. It gets down to -40 here, so we can’t go without the heat in the cold months. We’re looking at putting in a wood stove in the basement to offset some of the costs of gas.

  • Andrés August 21, 2016, 4:28 pm

    With the title “The World’s Most Efficient Air-Conditioner” and that pic I though you were to speak about the… trees!

    People in big cities go all concrete and a/c and forget of the usefulness of the trees. In summer their leaves protects us from the sun and in winter they let the sun warm us letting the sun shine through their naked branches.

    What a marvelous piece of technology! And don’t forget how they upgrade any picnic or nap when we sit on their roots…

  • Be October 6, 2016, 1:18 pm

    Does anyone had experience with heat/humidity acclimation for migraine sufferers? My hope is that as I become more accustomed to the heat and humidity it will be less and less of a migraine trigger.

  • Dominic June 19, 2019, 6:40 pm

    When I was in college in Tucson I made a vow never to use air conditioning, even during the summer. I lived in a second floor studio apartment with only one window. Even still it never got above 90 degrees inside. I slept using a wet towel as a blanket. It was tough at first but you do indeed get used to it. My electric bill was usually under 20 dollars with an all time record of $17.23.


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