But if you reach behind your wooden blinds and the air is hot, that heat is in your house...
Stop right there. You CANNOT reach behind the wood shutters in my house. The wooden shutters are within the frame of the window. The entire thing is enclosed in the window housing. The only heat that escapes is between the wooden slats and the joints. We are talking about heat so little that if you put your hand on the wooden slats you would not feel the heat from the other side. The inside of the wooden slat is as cool to the touch as if you were touching the inside wall of your home. There is almost no heat lost to the inside of the house, it's negligible. My A/C unit is NOT cooling the hot air in between the glass window and the wooden slats, it can't reach it. The air can't fit between the wooden slats to even reach that small pocket of air. Almost ALL of the heat is contained within the window enclosure except for an amount so small it's not worth mentioning. Below is a picture of something similar. These slats all fit very tight and are overlapping so that almost no air escapes. I'm sorry but my A/C is NOT cooling that air. It can't reach that air to cool it. Some of the heat is escaping into the room, but it's extremely small. I'm sorry but I have a house too and I know what I'm talking about as well as I've actually done some research on this topic. I'm sure there are better ways to do it, but you are over simplifying it tremendously. You need to do some research on your own and not simply listen to your brother. Surely you can get higher efficiency as well but you are NOT reaching 100% by simply reflecting the UV rays on the outside of your windows, no where NEAR that high. You are misleading people tremendously. Shutters work. I'm sorry that you don't agree, but you and your brother are incorrect.
https://www.jcpenney.com/p/jcpenney-home-faux-wood-plantation-shutters-with-mid-rail-2-panels/pp5003990767?pTmplType=regular&rrec=true&rrplacementtype=product1_rrI found something that suggests it's even a lot better then what I thought. Go do some research on it.
http://chemung.cce.cornell.edu/resources/energy-saving-window-treatmentFrom that article and the table at the bottom of it, the type of wooden slats I'm referring to are about 75%-90% effective at reducing heat exchange. Your wall is about 94-96% effective.