JUL 25

Nice idea. Along the same lines we could be looking at lighter-coloured materials for highways and parking lots. Let's not forget, though, that some of those roofs might be more useful if covered with solar cells.

Imagine if all the data and power transmission lines on the telephone poles had white insulation...

What about here in Canada where we only get two or three months a year where it is hot enough that having a white roof would be helpful... does it make sense to still do it here?

This suggestion is surely EarthCrime. The roofs will reflect heat back into the atmosphere, whereas dark roofs absorb the heat and conduct it to ground and the materials of the building itself.

Also, reflecting the energy away is a criminal waste of energy. That energy could have been captured and converted into electricity or thermal store.

The white roofs will almost certainly also increase the severity and distribution of extreme thunderstorms in the summer, marshalling more storms into large urban areas.

I'm amazed to hear about this. I think it's a great idea to paint roofs white, but will it have the same effect in colder countries?

Painting things white is done to slow Global warming. They are even paint mountains white to stop snow melt.

White reflects the light back into space.
Black absorbs the light are radiates heat back. So black increases the amount of heat in the atmosphere.

Time to go to the library and read a little thermoDynamica

Phil Plasma: That's a good question.

Fortunately, it doesn't look like a problem:

The places where you want to keep buildings cool are near the equator, where painting roofs white has the biggest effect on the Earth's albedo. So it is a double gain - more heat reflected straight out, less cooling required inside.

The places where you want to keep buildings warm are at the higher latitudes. The sunlight is more oblique, and more has already been scattered by the atmosphere. So painting roofs has limited benefit in albedo, and hurts you when it comes to heating. So you don't bother.

So it depends where you are. Anywhere you run a/c much of the year, it is a definite win.

Check out how some buildings are already saving. Today, the U.S. Environmental Protection Agency’s (EPA) ENERGY STAR program marked the midpoint of its 2011 National Building Competition: Battle of the Buildings. In the first six months of the competition alone, the competitors together have saved more than $3.7 million on utility bills and prevented 18,500 metric tons of CO2 emissions – that’s equal to the electricity used by 2,300 homes annually.

Teams from 245 buildings around the country are going head-to-head in this year’s ENERGY STAR National Building Competition to see who can reduce their energy use the most. The building with the largest percentage reduction in energy use, adjusted for weather and the size of the building, will be recognized as the winner in November.

Today EPA announced the Top Contenders for each of twelve building categories, including Boston’s Colonnade Hotel, the First Unitarian Society of Minneapolis, Office Depot in Plano, Texas, and a parking garage at the University of Central Florida.

There’s a lot we can all do in our own workplaces, as well. Actor John Corbett, the 2011 ENERGY STAR National Building Competition spokesperson, offers some tips in a new video posted today on the ENERGY STAR site www.energystar.gov/battleofthebuildings.

ENERGY STAR was started by EPA in 1992 as a market-based partnership to reduce greenhouse gas emissions through energy efficiency. Today, the ENERGY STAR label can be found on commercial and industrial buildings as well as new homes and more than 60 different kinds of products that meet strict energy-efficiency specifications set by EPA. Last year alone, Americans, with the help of ENERGY STAR, saved about $18 billion on their energy bills while preventing greenhouse gas emissions equivalent to the annual emissions of 33 million vehicles.

For a list of National Building Competition Top Contenders and complete midpoint results for all competitors: http://www.energystar.gov/BattleOfTheBuildings

Although the cost savings are significant the whole picture must be analyzed. Roofing is not inexpensive and paint will easily crack under extended sunlight. I've heard a lecture or two about how white roofs are worse, because the technology is not developed, or implemented correctly. I'm not saying its a bad idea, it just needs lifecycle analysis.

Why not make a roof that has a switch to flip it from a white side, to a black side, and vise-versa? That way, in the winter, when the sun is needed to heat, you can flip it to the black side, and during the summer, you can flip it to the white side.

I've heard this said before, so why are urban planning regulations not amended to ensure that all tall flat roofed buildings have a white surface area on top?
Surely the way to get it picked up is to lobby the planners?

If we didn't have insulation in our northern homes, then having a dark roof in the winter would help with reducing heating required in the house. But most of us have insulation making a dark roof barely any benefit to our heating bill and a white roof a huge benefit to reducing climate change.