How effective are passive cooling techniques? Which are the cost-effective and easy to use ones?

Do things painting the roof white help to reduce the heat in a significant way? Have seen it being mentioned in videos on black vs white coloured cars.

Are there any drawbacks noted by people who tried it for roofs?

Yeah it works. The drawback is you gotta do it.

If you’re only fighting heat and have a tall area then transom windows can also help a ton but you have to have a massive gigabrain from 1950 to understand how to use em.

Transom windows are the type that are above doors?