It was the summer of 2005, and a heat wave was sweeping across Ontario. At the time I was working on my engineering degree at the University of Waterloo, and tuition was just a little steep. As such, I lived in a cheap student house with no air conditioning. Fueled by a combination of too many engineering courses, too little money, and an overarching desire to not die of heatstroke before I graduated, I made my own air conditioner.

I put a few pictures of it on the internet, and then things got a little crazy thanks to Slashdot. I was featured on CTV’s Canada AM, had stories in The Kitchener-Waterloo Record and a few other newspapers, and was interviewed by a few radio stations including CBC Radio and NPR.

When you get down to it, it’s a basic heat exchanger, using water as the medium. You’ll probably need to fiddle a bit with the dimensions of the supplies based on your resources and preferences.

I’ve migrated this site a few times – first from the University of Waterloo servers, with their ever-patient admins, and then from a separate micro-site on this blog. This is my personal “blast from the past” that I’ve preserved for the sake of memory – it made for a rather entertaining summer!

Original Air Conditioner Concept

This is the first version of the air conditioner I made. Click on the pictures for more details.

Geoff’s Original Homemade Air Conditioner
Heat Exchanger
Water Supply
Technical Notes


Final Design

This is the final design I settled on after fiddling for a while.

The Black Beauty


Other Designs

These are some homemade air conditioners other people from around the world have made.

Pete’s Homemade Air Conditioner
Anonymous’ Homemade Air Conditioner
Spencer’s Homemade Air Conditioner


19 thoughts on “Homebrew Air Conditioning

  1. Pingback: Anonymous
  2. Geoff, I actually made a version of this using a huge 20″ industrial fan with coils on the front of the fan. Unfortunately, no matter how cold or how much water i pumped through the coils, it always warms up about less than halfway through the coils before making it all the way through. I can hardly feel a difference in room temperature.
    Does the size of the fan or fan speed have anything to do with this? Maybe it doesn’t work when the fan is too big and too fast? What I mean is the rate of cooling simply cannot catch up because the diameter of the fan is too big and the rate of air flow is too great.

    • Hi Joe – Yep, sounds to me like the fan is just throwing too much heat for the coils to deal with. The coils are actually from the very first version I made and are not nearly as efficient as using a radiator – especially in high-load applications such as yours. If you’re going to use a big fan like that, you need an equally big heat exchanger, and the coils just aren’t going to cut it. Try a local surplus or parts store.

  3. hey geoff
    awesome idea and i tried it.
    the first time siphon worked and all was good.but then the second time the water refused to even rise up through the tubing plz help me quick.

      • I was just wondering how you would make a larger system for a farm house out in the middle of the country. This looks and sounds amazing!! I have constant running spring water from a large spring that is filtered through a large limestone bluff it stays cold around 36 degress year round. Can you help me? I have my water running all year long, that also helps water the other animals out in the wild, because it runs out into a large pond about 200 feet from the house, it also feeds a duck pond as well from a seperate line from the spring, my spring water holding tank is built at the base of the bluff and is about 25’X 30′ approx. 4 feet deep, it says full all year long.


        I forgot to mention that the spring water is gravity flow to the house.

        • Hi Donna,

          If you have a gravity fed flow of cold water to the house this is pretty much the perfect situation, as you’ve eliminated pump sizing and power issues. I would recommend a setup where the water is first fed through a screen (to avoid any radiator clogging issues), then to a radiator, then off to the duck pond/etc. Major concerns would be preventing leaks and setting the radiator up in a location where any leaks can be handled easily (ie a basement with sump pump or similar).

          A lot of this design is going to depend on specifics of your house and just precisely how much and what you want to cool – let me know how the project goes!

  4. hey geoff- thanks for the reply but i figured out an easier wy to start the siphon.
    I fed water from the outside part of the vinyl tubing which then create a vccum inside the the tubing and starts the siphon in abt 20 secs.

    Cheers, Im freezing

  5. I hate to bother you but what style and size fan do you recommend? I need to be able to supply AC into a10x8 room. Thanks again Geoff, I will make sure I mention you and give them info about your wonderful invention! I cant wait to give a AC fan unit to someone in desperate need. I just need to make them at the least expensive way to be able to give away more. I sure hope I CAN make one:- I am going to follow your instructions and hopefully I will get donations at a fundraiser I’m trying to get together. Thanks for any advice!

Leave a Reply

Your email address will not be published. Required fields are marked *