Dive summary:

• Surveys have found that home buyers would rather get long-term energy efficiency in a new house than a price reduction now, and lightening up on roofing is a way to significantly reduce the energy needed for air conditioning.
• There is a range of products – reflective paint, vinyl sheeting, light-colored gravel for flat roofs – to move buildings toward the cool goal of soaking up less heat, and green roofs can help, too, because they don't reflect as much light, but the plants in them help release it and they are excellent insulation for the space below.
• Studies in California found that non-reflective roofs required air conditioning units to draw up to 15% more power than systems needed with reflective roofs.

From the article:

In most American urban areas, up to a quarter of the land area is made up of roofs. ...