How to Slow Warming: Paint Everything White

[Simplicius]

It's also well timed. Akbari pointed out that by his and his colleagues' calculations, the plan could save Americans $2 billion annually in unspent air conditioning, even after taking into account the increased need for heating in winter.

...And if weatherization got the attention, funding, and manpower it deserved, even winter heating would not be a significant issue. That would also go a way toward reducing actual energy consumption; in the US for instance 59 gigajoules of residential energy consumed is waste.* Significant reductions of this could be made using entirely passive means if homes were new-built and retrofitted wherever possible to a high standard of weatherization.

(* Source is Lawrence Livermore National Lab US Energy Flow--2002.)

Using reflective roof materials would give a threefold benefit; in addition to global albedo (if used widely enough) and energy efficiency through reduced cooling loads (which would give individual and larger-scale savings), reflective roofs have lower roof temperatures and therefore longer-lived materials. I don't recall the exact figure, but standard white shingles have at least 5 years' more service life than black, and white shingles aren't even especially reflective compared to other roofing materials.

Bill Rose at the Attic Performance Project gives a solar absorption rate of 0.77, compared to 0.94 percent for dark shingles, measured at their test structure (PDF paper; figures on page 3). The Lawrence Berkely Lab has been testing roofing materials as well and maintains a database; according to them even white asphalt shingles fall short of other materials. The lowest-performance metal roofs give roof tempertures equal to premium white shingles but with almost double the reflectivity, and the majority of tile types also outperform the premium shingles. White roof coatings blow any of these materials out of the water, of course, but they do seem to be less common, at least for residential application.

Asphalt shingles:

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   Product      |   Solar   |Infrared   |Temperature |Solar Reflectance| Reference
                |Reflectance|Emittance  |   Rise     |     Index       | 
-----------------------------------------------------------------------------------
White           |  0.21     |   0.91    |     68 F   |        21       | LBNL 1
-----------------------------------------------------------------------------------
ISP K-711 White |  0.36     |   0.91    |     55 F   |        40       | LBNL 2
-----------------------------------------------------------------------------------
ISP K-711 White |  0.31     |   0.91    |     59 F   |        34       | FSEC 1
-----------------------------------------------------------------------------------
Shasta White    |  0.26     |   0.91    |     64 F   |        27       | FSEC 1
-----------------------------------------------------------------------------------
Generic White   |  0.25     |   0.91    |     64 F   |        26       | FSEC 1

Compare this to other common residential roofing materials:

Metal roofs:

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   Product            |  Solar    |Infrared   |Temperature |Solar Reflectance| Reference
                      |Reflectance|Emittance  |   Rise     |     Index       | 
-----------------------------------------------------------------------------------------
New, bare             |  0.61     |   0.04    |     55 F   |        46       | FSEC1
galvanized steel      |           |           |            |                 |
-----------------------------------------------------------------------------------------
Aluminum              |  0.61     |   0.25    |     48 F   |        56       | FSEC 1
-----------------------------------------------------------------------------------------
MBCI Siliconized      |  0.59     |   0.85    |     37 F   |        71       | FSEC1
Polyester White       |           |           |            |                 |
-----------------------------------------------------------------------------------------
Atlanta Metal Products|  0.67     |   0.85    |     28 F   |        82       | FSEC1
Kynar Snow White      |           |           |            |                 |

Tile:

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  Product          |  Solar    |Infrared   |Temperature |Solar Reflectance| Reference
                   |Reflectance|Emittance  |   Rise     |     Index       | 
-------------------------------------------------------------------------------------
red clay tile      |  0.33     |   0.9     |     58 F   |       36        | FSEC 1
-------------------------------------------------------------------------------------
red concrete tile  |  0.18     |   0.91    |     71 F   |       17        | FSEC 1
-------------------------------------------------------------------------------------
unpainted cement   |  0.25     |   0.9     |     65 F   |       25        | FSEC 1
tile               |           |           |            |                 |
-------------------------------------------------------------------------------------
white concrete     |  0.73     |   0.9     |     21 F   |       90        | FSEC 1
tile               |           |           |            |                 |
-------------------------------------------------------------------------------------
concrete tile,     |  0.63     |   0.9     |     30 F   |       76        | LBNL 4
light beige coating            |           |            |                 |
-------------------------------------------------------------------------------------
concrete tile,     |  0.42     |   0.9     |     50 F   |       48        | LBNL 4
light brown coating            |           |            |                 |
-------------------------------------------------------------------------------------
concrete tile,pale |  0.41     |   0.9     |     51 F   |       46        | LBNL 4
bluish purple (mauve)          |           |            |                 |
-------------------------------------------------------------------------------------
concrete tile,     |  0.53     |   0.9     |     40 F   |       63        | LBNL 4
pink & gray coating|           |           |            |                 |
-------------------------------------------------------------------------------------
concrete tile,     |  0.74     |   0.9     |     20 F   |       92        | LBNL 5
off-white coating  |           |           |            |                 |
-------------------------------------------------------------------------------------
fiber cement,      |  0.26     |   0.9     |     64 F   |       27        | LBNL 5
earth brown color  |           |           |            |                 |
-------------------------------------------------------------------------------------
fiber cement,      |  0.25     |   0.9     |     65 F   |       25        | LBNL 5
pewter gray color  |           |           |            |                 |

Also, Einhander, I am going to go at you because I couldn't even find a link to a frothing whackaloon blog warning of the sinister black-shingle lobby, because there's no such thing. Think before you post, man.

[Gil Hamilton]

I'm at a loss to understand why the people who make shingles would care. Skimmer has it that its because they are made of asphalt as a base and that's believeable. However, there hasn't been an industry out there recently that hasn't made a pretty penny on making money off of "energy saving" products and if there was a big demand for white shingles, I'm sure there would be roofing tile makers who'd make white tiles, market them as environmentally friendly, and sell them. There are people who make roofing tiles in other colors anyway, I mean, the house across the street from me has grey shingles on it. Clearly, the evil roofing conspiracy missed a spot.