Most home owners don’t wash down their homes enough to keep this effective. Many homes are so dirty and mildew covered that the color reflectance won’t work.
That’s why it would have to be hydrophobic, so the rain can do that type of maintenance for you.
Right. Who wants to have to constantly clean a white house? This idea is just not happening.
Mid-Atlantic region here...every year I have to wage chemical warfare on all the white trim and porch pillars on my house to get the black mildew off.