Save heating / cooling costs by instead constantly painting and repainting your roof white and black, as the seasons change! Results in full employment for house painters, too.


In temperate latitudes, people frequently heat their homes in winter and cool their homes in summer.

The Issue:

The main source of heat is the Sun. So in the hot summer, a homeowner would want their roof & sun-facing walls to be reflective. But in the winter, they’d want the opposite—the roof should ideally absorb all of the Sun’s energy.


In order to solve this home-temperature-adjustment problem while also providing new sources of income for house painters, the following twice-annual chore is proposed:

  • On the exact middle day of spring, homeowners paint their roof (and any walls that get direct sunlight) a bright white or silver (Figure 1).
Fig. 1: The reflective paint helps keep interior temperatures down in the summer. This can make the house more pleasant inside and may save on air-conditioning costs as well.
  • On the exact middle day of fall, homeowners paint their roof (and any walls that get direct sunlight) with a matte black paint (Figure 2).
Fig. 2: This dark roof absorbs more solar energy and helps heat the home in winter.

Easy Solution for Hot / Cold Climates:

If it’s always hot, just paint the roof bright white / silver. And if you live in a polar region, just paint the roof black no matter what. No need for seasonal repainting!


Although the exact degree to which this would help is a bit unclear, cursory searching online reveals some experiments in which a white and black car were left in the same parking lot, and the white car was ~110ºF while the black one got to ~130ºF. A mirrored car might have stayed even cooler!

PROS: This might actually work!

CONS: Roof maintenance is a dangerous job, so the additional man-hours spent painting- and re-painting roofs would probably lead to a bunch of extra falling-off-roof injuries every year.