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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.