Stephen Chu’s White Roof Proposal and Rush Limbaugh’s Response

White roofing on urban row homes in Philadelphia

White roofing on urban row homes in Philadelphia

It does not surprise me that Rush Limbaugh would think that Energy Secretary Stephen Chu’s proposal to paint flat roofs white is idiotic, but I found it rather amusing that he couldn’t even figure out how reflection works on his radio talk show this morning. This is a very simple idea, light colors are brighter or lighter than dark colors because they reflect more light. The key is to understand that light is energy and light that impinges upon dark surfaces is far more likely to be absorbed and converted to kinetic energy, a.k.a. heat. Although I’m not sure, I bet the reason for only painting flat roofs white is because slanted roofs will reflect the light such that it will travel through far more of the earth’s atmosphere and therefore almost certainly be absorbed by the air, whereas a flat roof will reflect the light nearly vertically and thus the photons will be far more likely to escape our atmosphere back out to space. The solution is simple and cheap, yet elegant in its simplicity.

I feel that anybody who has completed a high school education in this country should be able to come up with the explanation that I just gave above, but the sad fact is that probably the majority of American’s could not give such an explanation, despite the fact that the overwhelming majority of Americans have completed high school. Science has been the hallmark of the advancement of all civilizations, why is “illiteracy” in science (and innumeracy) so acceptable in our society? Although left wing extremists will jump at the opportunity to make Rush look stupid, the general public won’t care. Although it is possible that Rush was being disingenuous and really did understand the simple ideas behind the proposal, but feigned ignorance for political reasons, I am more inclined to believe that he was being honest when he said he didn’t understand how it works.

We really need to look at how we teach in this country, and start experimenting with radical new approaches because this perfectly illustrates how inadequate current methods are. I realize changes in how science is taught have been made since Mr. Limbaugh attended school, but I am quite certain that most recent graduates would respond similarly.

14 thoughts on “Stephen Chu’s White Roof Proposal and Rush Limbaugh’s Response

  1. Jim Tex

    Dr. Jason,

    Almost any angle of roof would benefit from being painted white. The sun is not always perpendicular to flat roof tops.

    1. Jason Underdown Post author

      I agree that painting any angle of roof white would reflect more light back to outer space, but there is a point of diminishing returns where it no longer makes economic sense to spend the money on paint and labor. You must also look at how much bang you get for your buck! Perhaps depending upon your building’s latitude, it might actually make sense to paint the southern exposure side of your slanted roof (or northern exposure side if you live in the southern hemisphere).

  2. Richard Warg

    Dear Jason-

    Ditto! I started re-painting my house white last week when it hit 111F.

    Upon reflection it seems clear that we must eliminate excessive black body radiation in residential areas.

  3. Concerened Citizen

    I stumbled upon your post through visiting one of your family member’s blog. I am sorry to say that said family member is far more intelligent and interesting. This family member is also far less hateful towards the right wing. What happened to you?

  4. ritublog

    Everybody is aware with the fact that darker materials absorb more heat from sun than white/light colors, but an interesting data I want to share that black surface in the sun can be 40°C (70°F) hotter than the reflective white surface. This phenomenon occurs in the case of roofs also and heated roof then transfer their heat to surrounded air and contribute to heat island effect, while reflective metallic/ ceramic roof can reflect 65-75 %solar light. According to California energy commissioner “White roofs can cut a building’s energy use by 20% and save consumers money,” and “The potential energy savings in the U.S. is in excess of $1 billion annually.”

  5. wookiemeister

    ok….a quick explanation of why white paint works to cool the planet……

    1 around 50 percent of sunlight is visible light

    2 around 50 percent of sunlight is heat (infra red – i will call it heat for the moment)

    3 visible light is a frequency of light NOT absorbed by the atmosphere. repeat not absorbed by the atmosphere in practical terms.

    4 some HEAT (infra red) from the sun IS absorbed by the atmosphere directly (greenhouse gasses which makes the atmosphere warmer).

    5 HEAT from the sun also warms the surface of the planet and this HEAT is then radiated back into the atmosphere again being absorbed by greenhouse gasses.

    6 visible light is poorly absorbed by the atmosphere/ greeenhouse gasses, some of it gets reflected back by the atmosphere.

    7 the visible light that doesn’t get reflected back by the atmosphere is either reflected by the surface (eg a snow field) or absorbed by the surface (an asphalt carpark/ road). this absorbed light heats the dark surface. this heat is then radiated into the atmosphere and is absorbed by greenhouses gasses making the atmosphere warmer.

    8 by painting your roof white and other surface you reflect around 50 percent of the visible energy from the sun, a significant amount of this is reflected back into space WITHOUT heating the atmosphere.

    9 by painting enough roofs you make buildings cooler and cool the atmosphere. air conditioning works easier to cool houses because they are cooler, perhaps you wouldn’t even need air conditioning?

    if you are thinking of using white paint to cool your roof you will need a special white insulative paint that both reflects the visible frequencies of light and stops infra red frequencies from heating your roof.

    the special paint (something like insultec a waterbased white insulatiove paint) does two functions it reflects half of the suns energy and the insulative properties makes conduction and radiation of energy into your roof space is significantly reduced.

    my house already has a pale cream colour to it but given a bit more time i will probably paint my roof and walls facing the sun sometime this summer (i australia it gets very hot here in summer)

    chu is making the assumption that a cooler roof and building will mean less energy used to remove heat from the building, he’s right. its good to see the americans are finally waking up about how to use energy efficiently. over here in australia many people have foolishly bought houses with dark roofs. i can only hope that the american influence will convince them to change their thinking.

  6. Peter Kaminsky

    I absolutely agree with Jason’s views. But i think the reason behind painting the flat roofs white is that slanted roofs are oriented at a certain angle w.r.t. to the horizontal axis which minimizes the amount of heat that can be reflected, compared to the flat roofs. One more thing, Considering to the Science literacy rate in our country, it is indeed a disappointing fact for us that countries like India and China have a great amount of science literacy compared to us and this makes them much more superior. By the way, i came across these excellentphysics flash cards. Its also a great initiative by the FunnelBrain team. Amazing!!!

  7. Alan Underdown

    I strongly agree that scientific illiteracy is a major problem for American (and Canadian) societies. The more people know about science, logic, and critical thinking, the less susceptible they will be to politically driven arguments that ignore and/or distort the facts. On the issue of roof reflectivity, I gotta tell ya that it’s cold up here in Canada and we like our dark coloured roofs in the winter. On the other hand, they do increase our air conditioning bills (and GHG emissions) in the summer. Perhaps someone will develop a “reverse photochromic” roofing material that turns a light colour when exposed to a high light intensity and turns dark when the sun is weaker.

    Alan Underdown
    Ottawa, Ontario Canada

  8. Nathan Pershner

    Thanks for the good and hard working blog!I agree that painting any angle of roof white would reflect more light back to outer space, but there is a point of diminishing returns where it no longer makes economic sense to spend the money on paint and labor. You must also look at how much bang you get for your buck! Perhaps depending upon your building’s latitude, it might actually make sense to paint the southern exposure side of your slanted roof

  9. Pingback: Paint it White: Energy Sec. Chu Directs DOE to Install Cool Roofs | ecopolitology

  10. Billy Bob

    You enlightened folks ever stop to realize that the square footage of rooftops on Earth is so minor that painting them white would be like pi-sing in the ocean? It wouldn’t matter one iota.


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