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