# Why don't air conditioners use cold outside air? **URL:** \ **Category:** Factual Questions\ **Created:** [July 12, 2012, 11:08pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056 "2012-07-12T23:08:12Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [July 13, 2012, 6:49pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/21 "2012-07-13T18:49:04Z")
with whole house fans, if you are in a heating climate, then you want to provide they are sealed and insulated during the winter. you want a tight air seal with insulation on the inside house side and maybe some additional insulation on the attic side of the vent. ---
**Author:** ![FoundWaldo](https://avatars.discourse-cdn.com/v4/letter/f/dfb087/32.png) [@FoundWaldo](https://boards.straightdope.com/u/FoundWaldo)\ **Post date:** [July 13, 2012, 7:11pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/22 "2012-07-13T19:11:10Z")
> [@R.P.McMurphy](#): > > I’m sorry sir, but you are incredibly uninformed. Think long term. Read up on the subject before you comment. I’m sorry sir, but isn’t the point of this very website for the uninformed to ask questions to become informed? If I’m so uninformed, inform me. If you only want to talk to people who already know everything, I believe you may be in the wrong place. ---
**Author:** ![FoundWaldo](https://avatars.discourse-cdn.com/v4/letter/f/dfb087/32.png) [@FoundWaldo](https://boards.straightdope.com/u/FoundWaldo)\ **Post date:** [July 13, 2012, 7:15pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/23 "2012-07-13T19:15:26Z")
> [@SmellMyWort](#): > > Re bolded part above: Why would the air inside your house be hot if you’ve been running the AC all day? Sorry, valid question. The normal situation is that I go to work during the day, have the thermostat set pretty high, then come home in the evening and want to cool the house down so I can sleep comfortably. I don’t like leaving the windows open overnight for security and because my cat has been known to push the screen out to escape. What I do today is open several windows around the house and turn on a couple of fans, and then go back around and close all the windows before I go to sleep. But it’s a hassle and I sometimes forget a window. I have a fancy HVAC system with fancy programmable thermostats that cost me many thousands of dollars. It would be nice to be able to just tell it “keep the house between these temperatures, using whatever combination of heating, cooling and outside air is most efficient.” I realize there are complexities I am not aware of - that’s why I came here to ask! ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [July 13, 2012, 7:38pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/24 "2012-07-13T19:38:18Z")
> [@Joey\_P](#): > > Unless there’s a good cross breeze, on my house at least, I still need a fan pulling air in. Also, I’ve found, that if instead of having a fan pulling air IN, I have a fan blowing air OUT I get a lot less bugs coming into the house. Also, I’d imagine that over the long run my screens won’t get as dirty either. Our return duct grille sits right under the dining area window, so does a pretty competent job of bringing in the outside air. On nights like it’s been recently, we open the bedroom window and the dining window and turn on the furnace fan only. It creates a decent breeze for us. Not all homes are configured the same, of course. ---
**Author:** ![Hampshire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hampshire/32/4887_2.png) [@Hampshire](https://boards.straightdope.com/u/Hampshire)\ **Post date:** [July 14, 2012, 12:26am UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/25 "2012-07-14T00:26:12Z")
> [@SmellMyWort](#): > > Why would the air inside your house be hot if you’ve been running the AC all day?. It’s not uncommon for a lot of houses that are exposed to direct sunlight all day to need excessive cooling at night even when temperatures outside drop. Exterior walls can absorb a lot of heat during the day and then later radiate it inward. Old adobe huts built in the southwest work this way (staying cool during the day and then warming at night) and it is also the principal used in modern Trombe walls. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [July 17, 2012, 4:36am UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/26 "2012-07-17T04:36:39Z")
Also, if no air get in from outside, then why can rain sometimes get in when it’s really pouring? I thought the entire idea was that it was pulling air from both the outside and the inside–like how it work in a car. Or are we not including self-contained air conditioners here? ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [July 17, 2012, 4:52am UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/27 "2012-07-17T04:52:18Z")
> [@BigT](#): > > Also, if no air get in from outside, then why can rain sometimes get in when it’s really pouring? I thought the entire idea was that it was pulling air from both the outside and the inside–like how it work in a car. > > Or are we not including self-contained air conditioners here? The evaporator (the part in the front) collects moisture from the air in your house. The moisture drips down the coils to the pan on the bottom, where it travels in channels\* under the compressor and the insulation to the back of the unit and out some drain holes\*\*. If it’s really pouring and/or the wind is blowing against it, the rain can be driven back into the house using those same channels. Too much and it’ll overflow into your room. A simple solution (assume the drains are clear) if this happens often is to tilt the unit a bit further. \*If you look at the bottom you can see how where the channels are stamped in the sheet metal. \*\*Not all have drains and some have drains with a removable rubber grommet in them. Some units are designed so that the waste water is scooped up by the rear fan and splashed against the condenser to aid it in removing heat from the living space. ---
**Author:** ![FluffyBob](https://avatars.discourse-cdn.com/v4/letter/f/ecb155/32.png) [@FluffyBob](https://boards.straightdope.com/u/FluffyBob)\ **Post date:** [July 17, 2012, 1:51pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/28 "2012-07-17T13:51:04Z")
> [@Snnipe\_70E](#): > > Hello. See above. Dude you posted the same minute as me. ---
**Author:** ![Snnipe\_70E](https://avatars.discourse-cdn.com/v4/letter/s/b5a626/32.png) [@Snnipe\_70E](https://boards.straightdope.com/u/Snnipe_70E)\ **Post date:** [July 17, 2012, 3:31pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/29 "2012-07-17T15:31:36Z")
> [@FluffyBob](#): > > Dude you posted the same minute as me. Yep you are right. Sorry. ---
**Author:** ![Zulema](https://avatars.discourse-cdn.com/v4/letter/z/db5fbb/32.png) [@Zulema](https://boards.straightdope.com/u/Zulema)\ **Post date:** [July 18, 2012, 5:49pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/30 "2012-07-18T17:49:26Z")
On a related note I’ve always wondiered why no one has invented a refrigerator or freezer that can work off of outside air in the winter. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [July 18, 2012, 6:09pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/31 "2012-07-18T18:09:19Z")
> [@Zulema](#): > > On a related note I’ve always wondiered why no one has invented a refrigerator or freezer that can work off of outside air in the winter. Someone has - it’s called a “windowsill.” ---
**Author:** ![lance\_strongarm](https://avatars.discourse-cdn.com/v4/letter/l/87869e/32.png) [@lance\_strongarm](https://boards.straightdope.com/u/lance_strongarm)\ **Post date:** [July 18, 2012, 6:17pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/32 "2012-07-18T18:17:18Z")
> [@Mangetout](#): > > Just a nitpick - when it’s cool outside, the unit will have to work _less hard_ to cool the inside air. Right. And it will reach the temp on the thermostat faster during each cycle. And if the air outside is as cool or cooler than the air inside, and there’s no sun warming up the place either, the AC should be able to just stop cycling until the next morning. ---
**Author:** ![lance\_strongarm](https://avatars.discourse-cdn.com/v4/letter/l/87869e/32.png) [@lance\_strongarm](https://boards.straightdope.com/u/lance_strongarm)\ **Post date:** [July 18, 2012, 6:18pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/33 "2012-07-18T18:18:21Z")
> [@Zulema](#): > > On a related note I’ve always wondiered why no one has invented a refrigerator or freezer that can work off of outside air in the winter. Or one that vents the stupid hot air outside in the summer instead of pumping it into your house! ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [July 18, 2012, 9:36pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/34 "2012-07-18T21:36:28Z")
> [@Zulema](#): > > On a related note I’ve always wondiered why no one has invented a refrigerator or freezer that can work off of outside air in the winter. I used to wonder about that, and then realized it was pointless. While the refrigerator itself would operate more efficiently that way, you’d add a lot in terms of expense and complexity - a hole out the back, a separate fan, sensors to detect temperature and humidity, etc. But perhaps even more significantly… where does the waste heat of a standard fridge go? Into the house. And if the outdoors is below the 40 F or 28 F, then you’re running your furnace to keep the house warm. So the wasted energy isn’t actually wasted because it reduces the energy requirements of the furnace. The only people who would benefit are those using cheaper energy sources (like natural gas instead of electric) and this is a tiny, tiny savings. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [July 18, 2012, 9:45pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/35 "2012-07-18T21:45:30Z")
there are made in place units that would place the condenser (heat dump) to another area (e.g. basement). the walls of these can be very thick with insulation. ---
**Author:** ![lance\_strongarm](https://avatars.discourse-cdn.com/v4/letter/l/87869e/32.png) [@lance\_strongarm](https://boards.straightdope.com/u/lance_strongarm)\ **Post date:** [July 19, 2012, 2:51pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/36 "2012-07-19T14:51:38Z")
> [@dracoi](#): > > I used to wonder about that, and then realized it was pointless. > > While the refrigerator itself would operate more efficiently that way, you’d add a lot in terms of expense and complexity - a hole out the back, a separate fan, sensors to detect temperature and humidity, etc. You could just have a vent hole, like with a range hood. You open it in summer and close it in winter. I have a baffle that vents all that warm, moist air from my dryer into my home in winter. In summer, I vent it outside. Same idea. > [@](#): > > But perhaps even more significantly… where does the waste heat of a standard fridge go? Into the house. And if the outdoors is below the 40 F or 28 F, then you’re running your furnace to keep the house warm. So the wasted energy isn’t actually wasted because it reduces the energy requirements of the furnace. The only people who would benefit are those using cheaper energy sources (like natural gas instead of electric) and this is a tiny, tiny savings. In the summer, it might make a difference though, especially since your fridge is on 24/7. ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [July 19, 2012, 4:50pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/37 "2012-07-19T16:50:09Z")
> [@FoundWaldo](#): > > Besides, people do incredibly complex things and spend large sums of money in the name of energy efficiency. They install monstrous solar arrays on their roofs. They buy ugly and overpriced cars just because they’re hybrid. They put in geothermal heat pumps. I’m not sure I completely buy the complexity or cost argument here. Unless the savings are obvious and relatively timely, and you’ve expressed your own healthy skepticism there, I think you are 100% correct. In my view, there are many people who do these things, not because they will make any difference, but because it makes the people “feel good about themselves,” the primary motivation, apparently, for large parcels of society. ---
**Author:** ![lance\_strongarm](https://avatars.discourse-cdn.com/v4/letter/l/87869e/32.png) [@lance\_strongarm](https://boards.straightdope.com/u/lance_strongarm)\ **Post date:** [July 19, 2012, 5:27pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/38 "2012-07-19T17:27:23Z")
> [@CC](#): > > Unless the savings are obvious and relatively timely, and you’ve expressed your own healthy skepticism there, I think you are 100% correct. In my view, there are many people who do these things, not because they will make any difference, but because it makes the people “feel good about themselves,” the primary motivation, apparently, for large parcels of society. How about, you know, feeling like they are doing something good for everyone? Using less energy in order to, you know, reduce pollution and carbon emissions so that future generations will have a better life? Nah. Couldn’t be that. ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [July 19, 2012, 9:59pm UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/39 "2012-07-19T21:59:13Z")
> [@lance\_strongarm](#): > > How about, you know, feeling like they are doing something good for everyone? Using less energy in order to, you know, reduce pollution and carbon emissions so that future generations will have a better life? > > Nah. Couldn’t be that. Or, how about, you know, convincing themselves that their efforts will make a difference, so that they can, you know, feel better about themselves? E.g. - I believe the entire climate is becoming warmer, due to a large number of factors, including the results of the industrial revolution, astronomical forces that we understand poorly, and geological events that are out of our ken, and if I just turn down my thermostat, I’ll make the world better for our grandchildren. Riiiiiight. ---
**Author:** ![Mdcastle](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@Mdcastle](https://boards.straightdope.com/u/Mdcastle)\ **Post date:** [July 20, 2012, 2:24am UTC](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056/40 "2012-07-20T02:24:49Z")
My father installed a system that would draw in outside air and blow it into the ductwork to be circulated through the house. Eventually he removed and scrapped it. The intake was low to the ground so it sucked in pollen and other crap, and it was only really useful the few Midwestern nights when it was cool and not humid outside and still hot inside. [Previous page](https://boards.straightdope.com/t/why-dont-air-conditioners-use-cold-outside-air/628056.md?page=1)