I live on the second story of an apartment complex. My bedroom receives direct afternoon/ evening sun and heats up to an unbearable temperature. That side of the room becomes so hot I can feel the heat off the wall. I currently have a single hose 12000 BTU portable Ac unit in the window that is also on that wall. My problem is that the Ac doesn't seem to be cooling as efficiently as it should, leading to high energy bills.
I have done my research now and have found out that the single hose unit wasn't the best investment as the design is inherently wasteful. (Wish I had found out earlier). So now I am trying to make the best use of it.
I bought a couple sheets of Reflectix insulation to cover the single pane window but I have to mount them inside as I am only renting and can't stick things to the outside. Which leads to one of my problems; the heat created between the window and the insulation is melting any type stick used by the tape or Velcro to stick the two together. Is there a product that is heat resistant that I could use that would work better?
I found a video on YouTube that shows how to "jerry-rig" the intake of my Ac unit to another hose to essentially make it a two hose system. My second question is; is this a good idea? @https://youtu.be/LlX-iKldMY8;
Thank you
Matt

Permatex 81160 | Liquid Gasketing & Silicone Sealants

If you can pipe a little water to the AC through one of those ice maker installation kits you can double the output and halve the energy use. You will need to also purchase a water valve operated with a solenoid to turn the water off and on and match the solenoid voltage to the voltage of your AC unit. One wire to the solenoid goes to common and the other to run that goes to the compressor. The "Run" wire also supplies the capacitor and the "Common" goes to the compressor. Mount the solenoid in a safe place and adapt it to turn the 1/4" line off and on, coil in the "up" position. The end coming out of the solenoid goes to a spray nozzle to spray the outside condenser coil. All you need is a mist, not much water, just enough to wet the coils. This will cut you energy use by about 40% and double the output in BTUs.

Are there neighbors live upstairs or downstairs? How do they cope with the heat?
Can you pour cool water on the wall outside and open the windows to let out the hot air before using the cooling system?
Can airflow be lead in from other direction?