Engineering News

Perhaps someone with the expertise could explain to me exactly where the reflected light (and its heat component) goes after it bounces off the roof?

Somehow I don't believe that energy makes it back into space so it's gotta go somewhere!!! None of the articles (and the experiments they herald) speak to that aspect.

Hooker

Hi

the reflected heat from the white roofs provides a marginal increase in the heat emitted from the earth.

There will, of course, be some heat that warms up the atmosphere, so there is some loss in the process.

Sleepy

<...heat from the white roofs provides a marginal increase in the heat emitted from the earth...>

This is incorrect. The heat that is reflected back is the same heat that would have been absorbed by the building before being re-radiated.

Think as the insolation being income, the heat coming off the building as being expenditure, and the fossil fuel being used to drive the air conditioning as capital.

Savings come in the reduction of consumption of capital that would have been expensed by the air conditioning unit in the process of driving away the absorbed heat that the building is now reflecting. The overall expense of the building is less, so the warming effect is less.

As long as the heat is not in my house I dont care where else it goes.

Try living at higher latitudes in winter, then. Brrrrrrrr!

Even better than a white roof is a double roof. While building microwave equipment shelters in the middle east, we built concrete block walls and a sloped roof. We then built a second sloped roof above the first, separated by about 4 inches, with a gap of about 4 inches along the ridge line of the second roof. The sun heated the second (upper) roof, and heated the air below. The hot air flowed up between the roofs and out the gap. The building stayed nice and cool (except for heat picked up through the walls) - noticeably cooler than a building with only one roof. Because these were mountain-top installations, we could not use air conditioning.