In an attempt to answer Mr Safety Concerns.
A sealed aluminum tube without any insulation in the sun, blinds up or blinds down would make little difference.
However, a sealed alluminium tube with insulation makes a huge difference. For the sake of simplicity..imagine a thermos flask in the sun, the outside would get hot but this heat to a huge extent would not be transfered to the inside..ie inside stays cool. with me so far?
Now put windows into the thermos flask and the heat has a route into the thermos flask warming up the contents. putting a blind over the window creates a small area of insulation, the air between the blind and the glass acts as insulation..not as efficiently as double glazing or triple glazing ect..but it does work.
Now i have no doubt whatsoever that you knew this all along but decided to play dumb just to create an argument or hope someone may say something you could pick up on and crow with delight at their mistake. A pathetic and obvious ploy.
As for your scenario of nightime temperatures. if the stated temperature was the temperature inside the property then closing blinds/curtains whatever will not help..as it is insulating the property not allowing the hot air inside to escape. similar principle as a house i winter..close the curtains to reduce the amount of heat escaping.