Does mint actually provide cooling properties, or is it just a sensation? Similar to how a ghost pepper can't physically light you on fire even though you feel like you are on fire. I guess you could get some temperature sensors and try applying a few things to see what actually affects temperature. Water works to cool by evaporation; the water absorbs heat and then that heated water evaporates in to the air carrying away the heat. It could be that volatile compounds in mint oil evaporates off in a similar manner. I would just be very
concerned with having the sensation of feeling cool while not actually lowering your body temperature. I keeled over with heat stroke last summer and trust me, you do not want to ignore the signals your body sends when it absolutely needs to cool down. I was always really good at hydrating and keeping my body cool, except for about 6-8 minutes last summer when I ignored symptoms thinking I would get out before anything bad happened. I got out and promptly smashed my head into a door as I went down. I survived, but I can't say the same for my glasses.
I have thought about this a lot, particularly using thermal mass for cooling instead of heating. My case may be different than others as I have a very long wet season throughout the summer and fall, and it still tends to be occasionally rainy during our so-called 'dry' winter season. Lots of rain plus lots of sun equals high evaporation to the point that the air gets saturated with humidity. Having lots of cold surfaces means condensation in an already wet environment, and all of the problems associated with mold and other life forms growing where you may not want them. Perhaps having a permeable surface, or using the ground to pre-chill (and dehumidify) fresh air intakes would be useful.
Protecting your shelter from the sun is vital if you are going to cool a person. You can try to cool someone all you want, but if the house bakes in the sun all day and radiates that heat back in to the living space all night, you are fighting an uphill battle. Nearly all houses I see built in the US have roofs designed like solar ovens. Clear out all of the shade trees and now you have a very efficient solar oven. That might be a good design for a cold climate, but a lot of energy gets burned needlessly trying to fight the sun with an air conditioner instead of with shade and good design.
I envision a design where part or all of the structure is either underground or surrounded by berms like a wofati. The entire structure well shaded from the sun as to not absorb any direct radiant heat from the sun if possible. I also really like the idea of doing something similar to a large irrigation cistern, and using that mass pumped through a radiator/heat exchanger to cool and dehumidify air before being ducted indoors. With the large amount of rainfall in my location, I could make use of that resource to condition air to reduce issues with condensation and mold. This idea could also be used to cool a bench or other thermal mass where a person sits. I'd imagine very arid regions would have much fewer problems with condensation, but may not be able to have a large amount of water stored all year long.
Another idea along those lines that could be used in some circumstances might be something similar to this:
Except instead of cooling a computer, you could cool a chair or something. Or you could cool a computer to stop it from heating up your house. Or double the size of it and do both. If you are already planning earthworks then it could be easier to include plans for geothermal instead of digging exclusively for this kind of project.
I just really like the idea of using physical tons of mass to resist temperature changes. Massive benches, massive pillars, large water cisterns, lots of big masonry or recycled metal furniture. The current systems I see people using where they cool air, and the house soaks up heat all day is absurd. Especially at this time of year when it can get cooler outside at night than what people set their thermostat to, yet the AC runs all night because the mass of the house is saturated with heat, and people don't want to open windows and let all of the humidity inside. If they put efficiency ratings on houses the way they do on cars, it would make people think twice and save way more energy than squeezing out 1MPG extra from a car.