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.

Background:

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.

Proposal:

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!

Conclusion:

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.