Asklemmy

Yes, very effective. I worked in commercial construction for a few years.

We didn't use paint, but the gist is the same. A black EPDM roof may reflect about 5% of incident irradiance and a white TPO roof reflects about 80% which means that a white TPO roof reflects 16x more light than a black EPDM roof and the black roof absorbs 4.75x more than the white.

This means white is easier to cool in the summer and black is may be easier to heat in the winter, but the amount of sun in the winter is less so its not like 1:1.

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.

I live in south Florida and replaced/resurfaced the asphalt parts of my roof with white PTO and silicone elastomer. It lowered power usage from AC by about 10% in the main zone and much more in a smaller zone where the AC ran constantly because it couldn’t maintain the temp (77F) with the black roof. That seems to be in line with current research but YMMV.

https://www.youtube.com/watch?v=36D6CzghGfw

One of the drawbacks he found were moisture problems inside because of the cooler temperatures, but this was in his shed. Though he's testing more than just white paint, he's testing daytime passive radiative paint.

You can cover windows that get a lot of sun in one way reflective sheeting. The big downside is that it’s going to block the sunlight a bit as well, but it works pretty well.

Window awnings are also very good.

Easy and cost effective? Vines. You'll pay in labor tho.

Depending on your local climate, and also house's construction & siding, theres probably some non-destructive vines you can get going on trellises or wall-holds. They'll act as shade barriers to your wall, cool the surrounding air with evapotranspiration, and you can even get some beans out of it.

Downside is that same evapotranspiration is going to act as a wind barrier and potentially hold too much moisture in your siding, but thats usually easily fixed with regular pruning, and it'll be worst on the off-sun walls that need the least shading anyways.

Wrong type of vines can anchor roots directly into mortar/siding & damage the wall. so do your research. English Ivy can fuck off. Beans & cucurbits work well. Ive personally got Virginia creeper running up some of my brick side-walls.

Painting a roof white has shown a measurable lowering of temperature inside the building. Any issues are likely caused by the material used to make the roof white.

I forget what tropical place my parents went, but all the roofs were white for that reason