No Air Conditioning? You Have Options.

For those who don’t have A/C this sum­mer, or whose unit is cur­rent­ly not work­ing, there’s still a way for you to beat the heat with pas­sive cool­ing measures.

Dur­ing BC’s fatal heat wave of 2021, I used a set of Mylar blan­kets and a cou­ple rolls of Goril­la mount­ing tape to make expe­di­ent solar shield­ing, which got my house through the worst of the heat with­out any need for air con­di­tion­ing or per­son­al fans. When shield­ing is com­bined with draw­ing in cool air from out­doors dur­ing ear­ly morn­ings, the aver­age inte­ri­or tem­per­a­ture of the house will be a rel­a­tive­ly sta­ble 10–20°C less than the peak ambi­ent out­door tem­per­a­ture. This will get you through a heat wave, and if the insu­la­tion of your house is par­tic­u­lar­ly good, it will also deliv­er sub­stan­tial comfort.

Shield­ing Instal­la­tion:

1. Since ordi­nary soda-lime win­dow glass absorbs most wave­lengths of infrared (IR) light and con­verts that ener­gy into heat, you need to install your shield­ing on the out­side of the win­dow. This requires the glass to be clean. Wipe down each sur­face using glass clean­er or 50/50 white vine­gar and water, then dry com­plete­ly. There should be no drips remaining.
   
2. Cut and apply eight (8) one-inch pieces of dou­ble-sided mount­ing tape along the edge of the perime­ter of each win­dow. You should end up with a piece of tape in each cor­ner and one in the mid­dle of each hor­i­zon­tal and ver­ti­cal edge. The tape should be stuck to the edge of the glass but not touch­ing the frame, since the mount­ing tape is very sticky and may remove paint or oth­er sur­face coatings.
   
3. For met­al doors, you’re going to mod­i­fy your cov­er­age to include the entire door. Attach the tape along the out­er perime­ter of the door in each of the four cor­ners and one in the mid­dle of each edge, but be sure to avoid get­ting too close to the hinges or any oth­er object that might rub or tear the shield.
   
4. Remove the pro­tec­tive plas­tic back­ing from the mount­ing tape, expos­ing the out­er sticky side. The trick to doing this is to wedge the tip of a razor util­i­ty knife just below the sur­face of one cor­ner of the tape, between tape and back­ing, and pull out­wards. This should free the cor­ner of the back­ing and make it easy to lift and peel away.
   
5. On a flat area of the floor, com­plete­ly unroll and spread the Mylar blan­ket. Once it’s open, care­ful­ly lift and bring it near the win­dow. Stand in between the blan­ket and the window/door you are work­ing on. From here, hold the top edge of the blan­ket above your head and bring it into con­tact with the mount­ing tape along the top of the window/door.
   
6. Step back, mak­ing sure to hold onto the bot­tom of the Mylar blan­ket as you do, so that it does­n’t con­tact the sur­face yet.
   
7. Work­ing from top to bot­tom, care­ful­ly tack the Mylar blan­kets down to the win­dow, mak­ing sure to hold them taut for best appear­ance and reflec­tiv­i­ty. You don’t need to haul down hard on them, you just need to make sure the sur­face is flat with the win­dow. You can wipe your hand across the blan­ket to push out the air behind it and make it sit smooth and flat.
   
8. Once ful­ly installed and smoothed, the Mylar blan­ket can now be cut to the final out­line of the win­dow glass edge. A util­i­ty knife makes short work of this.
   
9. Move on to the next window/door and repeat until finished.

Because of the mate­ri­als used, the shield­ing is durable and weath­er­proof, and an added ben­e­fit of this method is it does­n’t inter­fere with the nor­mal open­ing and clos­ing of most windows/doors. You will still be able to use them while enjoy­ing pro­tec­tion from the heat. Goril­la mount­ing tape is ~1mm thick, mak­ing it com­pat­i­ble with slid­ing win­dows (the glass is nor­mal­ly recessed a few millimeters).

Dai­ly Air Intake:

Each morn­ing when out­door tem­per­a­tures are at their low­est, open all win­dows and doors to vent the house and take in fresh air. Once the sun comes up, close them again, and you should be left with enough cool air to get through the day.

If you have win­dow fans, these will speed up the process con­sid­er­ably. Stove range fans and bath­room fans will also pro­vide suc­tion to bring in cool­er out­side air faster — use them.

I hope these sug­ges­tions help.

P.S. yes, there’s a NASA tie-in. My inspi­ra­tion for this project was an inci­dent that hap­pened on Sky­lab. If alu­minized Mylar is good at fend­ing off 120°C in space, it’ll eas­i­ly han­dle any con­di­tions on Earth.