[JR: "Energy Star" white reflective paint.]

Given that in high latitude locations there are more dark hours than light hours in the winter, a dark roof is prone to radiate as more heat energy out of a structure at night than it absorbs from sunlight during the day.

This is so regardless of the amount of attic insulation. A well insulated attic obviously will reduce conductive heat loss. It also will equally reduce the amount of heat conveyed to living space from any energy absorbed by the roof during daylight hours. Any heat absorbed from the sun during the day still will be radiated away at night.

Overall, the benefits of reflective roofs are the same in both hot and cold weather: they reduce the flow of heat energy across the envelope of a building. This is the same reason that a thermos bottle is useful both to keep a cold drink cold and to keep a hot beverage warm.

Who is talking about (anyone talking about) this being a silver bullet? Just cause Joe says:

nobody here has proposed this as the solution to global warming…don’t attack strawmen…

doesn’t mean that anyone WAS SUGGESTING that anyone (here) HAD proposed this as the “the solution to global warming” (= silver bullet). I certainly did not suggest that anyone here, least of all Joe, had proposed this as “the” solution.

Where did THAT idea come from? Probably from my silly attempt to shoehorn my point into a paraphrase of a Prince song (may be qualified…never take the place…). So much for trying to be funny. Sorry about the confusion this caused. (But I certainly did NOT mean that anyone here had said that it COULD take the place of ALL or most CO2 reductions.)

For the record:

I think the white materials stuff is great, a no-brainer. Not that it matters, but I did say this in January.

Geoengineering approaches that focus on the radiative balance obviously need to be considered, to stave off some warming (and this one carries benefits in two additional dimensions, hence the win-win-win), but I see no reason to talk about the albedo effect in terms of “offsetting” CO2 (no matter the potential size of these effects).

Unless I misunderstood Joe in January, he seemed to agree that the pervasive use of the word “offsets” (as a verb) in the original article was unfortunate ( I believe he said it was a “dumb word”).

Therefore, I was surprised to see the figure caption in the current post use this word.

That’s all.

http://palingates.blogspot.com/ 2009/ 05/ sarah-palin-and-nobel-prize-winner.html

Incidentally, I’ve tried highly diluted outdoor paint (less than one part per hundred of paint), as a concrete cleaner. It makes older concrete look newer -by raising the albedo several percent. I suspect this technique could very cheaply make some modest difference, and you could probably use a street sweeper to apply it at very low cost.

I was curious about this too. Wikipedia has a fairly good well-sourced entry on this.

http://en.wikipedia.org/ wiki/ Cool_roof#Cool_Roofs_in_Cool_Climates

I think the heat loss from reflective roofs isn’t that substantial in colder climates largely because the sun is lower in the sky during the winter months to begin with (for the same reason, solar panels generate more electricity in the summer), heating demand is highest in the evening (where the roof feature wouldn’t make a difference), and cool roofs help retain snow in areas of moderate snowfall, which provides some insulation.