https://translate.google.com/translate?sl=auto&tl=en&u=https://www.n-tv.de/wissen/Farbe-kuehlt-besser-als-viele-Klimaanlagen-article22494982.html (https://translate.google.com/translate?sl=auto&tl=en&u=https://www.n-tv.de/wissen/Farbe-kuehlt-besser-als-viele-Klimaanlagen-article22494982.html)
It reflects more than 98 percent of the incident sunlight, and its surface remains 4.5 degrees Celsius below the ambient temperature even in the midday heat.
At night it is even 10.5 degrees cooler than the surrounding area. The researchers working with Xiulin Ruan from Purdue University in West Lafayette (Indiana, USA) estimate the cooling performance of the paint based on barium sulfate to be more than 100 watts per square meter
cool-electric development from 1982 comparison
https://worldwide.espacenet.com/publicationDetails/biblio?DB=EPODOC&II=14&ND=3&adjacent=true&locale=en_EP&FT=D&date=19910228&CC=DD&NR=287597A5&KC=A5 (https://worldwide.espacenet.com/publicationDetails/biblio?DB=EPODOC&II=14&ND=3&adjacent=true&locale=en_EP&FT=D&date=19910228&CC=DD&NR=287597A5&KC=A5)
After connecting an electrical resistor,
the room temperature dropped from 27 °
to 23 ° C, and 80 watts of electrical energy could be used per square meter of wall surface
a voltage of about 400 V.
https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=DD&NR=223743A1&KC=A1&FT=D&ND=3&date=19850619&DB=EPODOC&locale=en_EP (https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=DD&NR=223743A1&KC=A1&FT=D&ND=3&date=19850619&DB=EPODOC&locale=en_EP)
https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=DD&NR=208029A1&KC=A1&FT=D&ND=3&date=19840321&DB=EPODOC&locale=en_EP (https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=DD&NR=208029A1&KC=A1&FT=D&ND=3&date=19840321&DB=EPODOC&locale=en_EP)
I would have thought a mirror type surface would do better than that. More expensive, though.
" more expensive " : https://www.electrochem.org/ecs-blog/aluminum-foil-like-material-acts-as-cooling-system/ (https://www.electrochem.org/ecs-blog/aluminum-foil-like-material-acts-as-cooling-system/)
When only the function shall be irradiation blocking/reflection a kitchen IR radiation reflecting alu foil is more than enough !
https://www.quora.com/What-percentage-of-infrared-rays-does-aluminium-reflect#:~:text=The%20spelling%20aluminum%20was%20British,people%20are%20confused%20about%20that.&text=this%20frequency%20range-,A%20fraction%20of%20the%20incident%20energy%20in%20%E2%80%9Cinfrared%20frequencies%E2%80%9D%2C,a%20polished%20aluminum%20metal%20surface (https://www.quora.com/What-percentage-of-infrared-rays-does-aluminium-reflect#:~:text=The%20spelling%20aluminum%20was%20British,people%20are%20confused%20about%20that.&text=this%20frequency%20range-,A%20fraction%20of%20the%20incident%20energy%20in%20%E2%80%9Cinfrared%20frequencies%E2%80%9D%2C,a%20polished%20aluminum%20metal%20surface).
But our several social classes society wants basic/culture/luxury solutions !