Painting the Roof White

Most of the shingles that sell are gray. The reason is this: White repels the heat best in the daytime. But, at night, white releases heat slower than black. Gray is a compromise between the two.

They did a study on it, and found that lighter shingles cut overall energy costs.

http://www.azcoolroof.com/downloads/Resources/White%20Roofs%20Are%20A%20Cool%20Way%20To%20Cut%20Energy%20Costs.pdf

DrewDad-
Thank you.

However, the article is silent on higher heating costs in the winter. Perhaps because it was written for a Florida newspaper. I live in New York City.

No. White reflects light. It also radiates less heat. If the house is hot because of sunlight, white will cool it. If it is hot because of a heating system, the white color will radiate less than a black roof.

You're not going to get much direct sunlight in the winter (especially NYC) so it doesn't matter what color the roof is in the season where it's mostly cloudy most of the time.

The only time the color matters is when the sun is out the longest (spring and summer).

roger-
Thank you.

If the house is cold in the winter, would a white roof absorb the least heat and thereby result in an increased fuel bill to heat the house?

Unlikely. Lets put it like this. The color white will tend to maintain the internal temperature, whether it is hot or cold relative to the outside air. An ultra flat black will tend to make the interior temperature go up or down to match the outside air. Even in the absence of sunlight, those are still the tendencies.

My recollection from the article I heard or read is that it did slightly increase the winter energy costs, but that the summer energy savings were much greater.