00:00That empty 2-liter bottle in your recycling can drop the air that moves through it by 15 degrees
00:04on your skin. No ice, no plug, no compressor humming in the window. Today I'm going to show
00:11you how to turn six to nine of those bottles and a scrapboard into a window cooler that makes real
00:15wind out of barely any breeze for about three dollars, where to cut the plastic so it jets
00:20instead of whistles, how to seal it so you keep the pressure, and how to prove it works in 10
00:24seconds with a five dollar thermometer. I will also show you the damp sheet trick that triples
00:28how cold it feels when the day is brutal. My garage has run one of these the last two summers.
00:34When the wind lines up, you walk in and your face just does that. Oh, that is a different thing.
00:39Here's why it works fast, because once you see it, you will build it right without overthinking.
00:44Air spreads to fill space, force that same air through a narrow neck, and it has to speed up
00:48and its pressure drops. You know this from a garden hose. Thumb over the end, and water shoots.
00:53You did not add a pump, you narrowed the exit. Bottles do it in reverse. The wide mouth scoops
00:58a big column of hot outside air. The taper funnels it. The neck squeezes it into a fast jet.
01:04That jet hits you faster than the breeze that went in. Two things happen at the squeeze.
01:09A little bit of real cooling happens, because compressed air that gets room to expand again
01:13drops a few degrees. Hold a bike tire valve open against your hand and you feel it.
01:17But the big win is what that faster jet does to your skin. Faster air evaporates, sweat faster.
01:23Sweat needs heat to turn from liquid to vapor, and it steals that heat from you.
01:26A faster jet peels that vapor away quicker, so your skin reads 10-15 degrees cooler, while
01:31a thermometer on the wall might only show 4-7. That is not a trick. That is the same reason
01:3690 degrees with a breeze feels fine, and 90 with still air feels miserable.
01:42This board does not make cold like a fridge. It makes wind. And wind is your built-in air
01:47conditioner. I will tell you the one sealing mistake that turns the whole thing into a noisy
01:51whistle in a minute, because it is the difference between cold and nothing. You need almost nothing.
01:57One flat board to fill your window opening. Plywood. Rigid foam board. Even a double layer
02:02of thick cardboard, if that is what you have. It needs to close the window, not just sit in
02:07it. 6-9 clean, straight-walled 2-liter bottles. Coke or store seltzer. A marker. A sharp box cutter
02:13or scissors. A drill or a nail to start the holes. Optional, but worth it. A tube of silicone
02:18or hot glue and a roll of foam weatherstrip tape for $2. The board is about $3 for a quarter
02:23sheet offcut at Home Depot, or free if you have cardboard. The bottles are free. A small
02:28tube of silicone is about $4 and does 5 builds. Lay out first. Hold a bottle up and trace a
02:34circle about a third down from the cap, where the plastic is still wide and straight. For
02:39a 2-liter that is roughly 4 1⁄4 inches. Mark 6. Holes to start. Two rows of 3. About
02:479, 3x3. Nine moves more total air volume, but do not crowd them edge to edge. A little
02:53board between funnels keeps the jets clean. Cut the circles. Drill a starter hole inside
02:57the line, then follow the marker. Keep the edge clean. A ragged hole leaks and leaks kill
03:02the jet. That is the quiet failure most builds have. Prep the bottles. This is where people
03:07rush. From the cap down, measure 5 inches and cut straight around. Keep the cap on. You want
03:13the top funnel piece. A little megaphone shape. If the cap has that tiny inner seal ring inside
03:18the hole, nip it off with the cutter so air does not catch. You should have a smooth funnel
03:23with a clean round neck. Short squat water bottles with wavy ribs tumble the air. Tall
03:28straight soda bottles make a clean, fast jet. Pick the straight ones. Seat them. From the
03:33outside face, the side that will face the hot outdoors, push each funnel through so the wide
03:38mouth faces out and the narrow neck sticks into the room. All caps point in. All mouths face
03:43out. The plastic shoulder should catch on the board. If it slides through, wrap one
03:47turn of tape around the shoulder to snug it. Now that sealing mistake. Run a thin bead
03:51of silicone or hot glue right where each neck meets the board on the inside face. Run foam
03:55tape around the aew, the whole board edge, where it meets the window frame. Any air that
04:00sneaks around the funnels or around the board is air that did not get squeezed, so pressure
04:05drops and the jet goes soft. A cheap board sealed perfectly will beat a pretty board that
04:10leaks every time. Let it tack 20 minutes. You want one path only. Outside, through bottles,
04:16into room. Mount it tight like a shutter. Foam tape compresses and closes gaps. Close
04:21the rest of the window hard against it. You need exhaust too. Crack a door or a second window
04:26a half inch on the shady side of the house. Bottle window is intake. A little crack is exhaust.
04:32Without that, the room pressurizes and the breeze just stops, like trying to drink through
04:36a straw with your finger over the other end. Proof test right now. Tape a kitchen thermometer
04:416 inches inside one bottleneck and hold another thermometer outside in the shade. On any day
04:46with even a light breeze, you can feel on your cheek. You will see 2-4 degrees of real drop
04:51on the wall after a minute and 6-10 if you hold the probe straight in the jet. Put your
04:56hand there instead and it feels like the 15 degree promise because your skin adds evaporation.
05:01If you see nothing, your board leaks or your funnels are backward. 5 second fix. If you
05:06like fixes that pay you back the same afternoon, hit subscribe. And if you want the printable
05:12cut template for 6 to 9 bottle spacing plus the exact damp setup I use. That is on the
05:17membership with the printable sheet.
05:18Now, the damp sheet trick I promised. Hang a thin bed sheet or big towel lightly dampened
05:25about a foot inside the board so the jets hit the fabric without touching it.
05:29Now you have stacked two coolers. The bottles accelerate air. The damp cloth donates water
05:35for evaporation. In dry or average humidity, that combo pulls what your skin feels down 12-15
05:41degrees below outside. And a wall thermometer in a small room under 150 square feet will
05:46finally move 5 to 8 degrees. In muggy sticky air, it still helps. But less because air
05:52already full of water cannot take more sweat. That is not a flaw. That is just how evaporation
05:57works. Before you overbuild, let me kill the myths that waste time. More bottles does not
06:03mean endlessly colder. Cooling per jet is fixed by the squeeze. Six well-sealed funnels beat
06:0812 sloppy ones with gaps. Seven, eight, nine help because you move more total air. Ten and
06:14eleven add almost nothing while you lose board strength. Painting the board black hurts. People
06:19think black absorbs heat and helps. A hot board heats the air touching it. Leave the outside
06:25white or tape foil to it. You want the air hitting the funnels as close to shade temperature
06:30as possible. This does not refrigerate a sealed box with no air exchange. Anyone telling you
06:35a bottle board replaces a refrigerant AC in a closed room is selling a story. It is a wind,
06:41amplifier, and personal cooler. Once you accept that, it becomes absurdly useful because most
06:45hot rooms already have one thing. A window with a little outside air doing nothing. And
06:50the ribbed bottle shape matters. Those hard grip ribs and cheap water bottles create turbulence
06:55inside the taper and the jet goes fuzzy. Use the tall, smooth taper. Money next to the alternative.
07:01Because that is why this sticks. A small 5000 BTU, window AC, is about $150 at Walmart right
07:09now. Pulls roughly 500 watts. And at 14 cents, a kilowatt hour costs about 45 cents an hour
07:16to run. Eight hours a day for 90 days of summer is about $320 in electricity, plus the $150 to
07:22buy it. $470 for one room for one summer. This board is zero to three dollars if you have cardboard.
07:29About 7 if you buy an offcut in foam tape. And zero an hour after that, because wind pays
07:34the bill. Use it 30 afternoons when it is too hot to work in the garage, and you dodged
07:39about $108 in runtime alone. Run it most of the summer in a shed or small bedroom instead
07:44of a portable single hose unit, and you are $300 to $400 ahead without thinking. The wind
07:49was already there. Three tiny tweaks beat rebuilding. Keep that cap hole perfectly round, and that
07:56little lip off. A clean circle shoots straight. A nicked edge makes turbulence you can hear as a
08:01whistle. If it whistles, you lost speed. Two, point the board dead square to the breeze, not square to
08:09the house. Tape a ribbon to an outside funnel. When it points straight out from the board, you are square.
08:15Five degrees off still works, 15 off, and outside air slides across the mouths instead of into them.
08:21Three, put the board high in the window. Not low. Hot air pools at the ceiling. Pulling from higher
08:27outside and exhausting low on the opposite side. Flushes heat instead of recycling it. And lightly
08:33seal raw plywood edges with tape, so a damp sheet nearby does not swell the board and open gaps.
08:38Wash the funnels once a month. Dust in the taper steals 10% before you notice. So that is it.
08:44Whiteboard
08:45with six to nine straight two-liter funnels. Mouths out, necks in, necks and edges sealed. Tight in the
08:51windward window with a hair crack open downwind. Damp sheet a foot inside if the air is dry. Light
08:57breeze outside. Noticeably faster, cooler feeling air inside. No watts, no hum. Beyond a little hiss that
09:04tells you it is working. If this drops your shop even five real degrees, share it with the neighbor who
09:09keeps saying it is too hot to work out there. See you in the next one.
