If you prevent heat from entering your house, you don't have to get rid of it either.
The last two days I hung up two wet towels as "curtains" on the outside of (open, curtainless) window in the living room, which face the sun during the day. They blocked the sun, and air coming into the house through the window was notably colder.
They dried out so quickly that I had to soak them again twice during the day. Given how much energy it takes to evaporate all that water I think that little hack got rid of a lot of heat.
It looks terrible-slash-suspicious but I've found covering windows with aluminum foil to be an effective technique. It's cheap, reflective, and optically thick.
Yeah, that would work even better at deflecting heat - there's a reason chemists and physicists use simple aluminium foil as make-shift insulators (might also block some the neighbour's WiFi signal, boosting the reception of your own, but that's a bit of a tin-foil hypothesis :P).
You'd miss on the evaporation cooling though. Maybe a two-layer approach would work best of all low-tech hacks! :)
In the past, when I was living in an apartment with a wider windowsill, I used to put a reflector made from cardboard covered with aluminium foil on the inside and sun-hungry plants inbetween, creating a miniature greenhouse. Open windows were a requirement of course, because it would still trap heat otherwise.
I live in a place with abundant water, but I would expect this approach to be kind of "frowned upon" in a desert. Isn't saving water a high priority in those environments?
The last two days I hung up two wet towels as "curtains" on the outside of (open, curtainless) window in the living room, which face the sun during the day. They blocked the sun, and air coming into the house through the window was notably colder.
They dried out so quickly that I had to soak them again twice during the day. Given how much energy it takes to evaporate all that water I think that little hack got rid of a lot of heat.