May 27 2009, 9:23AM
Really? The White Roof Solution.
We've come to expect that the "solutions" to Climate Change will be high tech--floating windmills, underwater generators, and nano solar in the Jules Verne/James Bond tradition--or at least high concept (carbon credit trading). But this week Energy Secretary and Nobel Prize winner Steve Chu is in Europe extolling the benefits of ... white roofs. The concept is simple but the numbers he cites are massive: Making roofs and pavement more reflective could offset 44 billion tons of CO2, or the equivalent of taking all of the world's cars off the road for 11 years. (While these numbers appear huge, there's no mention of the time frame, so they're not comparable to other numbers.)
Even so, these numbers are an interesting reflection of how much we've re-engineered the planet and climate already, and how we might start to mitigate that. Chu seems to want us to understand this as a category-jumper, working on climate in a different way than changing energy sources or sequestering carbon, and so he describes increasing the albedo (reflectivity) of buildings and pavements as "geo-engineering."
I guess it's predictable that some media are already making fun of Chu. Perhaps the idea is too simple and sensible, or just too eggheaded. (In California a related proposal to require that car roofs be more reflective as part of the state's climate policy became controversial. There's something about the brainy dumbness of the idea that doesn't float politically.) Over at google's geo-engineering forum, though, they're worried that the reception for Chu's idea is an indication of the ridicule the public may heap upon heavier geo-engineering against climate change--things like stratospheric aerosols and cloud whitening. A few years ago, discussing geo-engineering in polite company was pretty much off limits because it muddied up the discussion about when to take action on climate change. But as action has been delayed, and fear has grown, the concept has moved steadily towards the far outskirts of the center. Chu's use of the term geo-engineering in this relatively benign context is an indication of where the discussion is headed.
Lisa Margonelli
The city of Chicago already requires that all roofs be painted silver or white - it's part of the building codes here. I believe the rule went into effect about 5 years ago. It cuts down on energy costs and reduces the summer temp highs in the city - it makes sense locally as well as globally.
Actually this is the first bit of common sense in regards to man made climate impact.
CO2 is symptomatic of a larger problem which has to do with irradiation, but also carbon displacement in regards to land and oceanic based eco systems.
This is a far more effective approach than Cap n Trade or carbon taxes.
Aluminum or white reflective coatings dramatically affect the inside temperatures of buildings in the summer with significant under-roof cooling. The result is lower A/C costs which directly means lower energy costs which translates to a lesser carbon footprint. Further reflecting the heat up and out to space is also measurable, but will leave those calculations up to Steve Chu. In my mind, the KISS principle is clearly at work here. Keeping it simple will yield significant, measurable and quick results.
The two mistakes that people make when they hear about this stuff is to think it's new and that it will work in all cases.
First of all aluminized roof coating has been around for ages. It is used to protect flat roof from the harmful effects of sunlight. That is the same principal behind that granular coating on ordinary roof shingles. Regular application of roof coating (it goes on like paint and dries bright silver) preserves the roof, whether built up tar or rubberoid. The maintenance instruction for rubberoid (the most popular flat roofing today) specifically call for coating with aluminum roof coating on a 5 year schedule. Of course, if a low pitch roof is covered with selvege (split sheet roll roofing) or 90 lb. roll that comes with a white of black granular coating to repel sunlight.
White roofs reflect sun (heat) while dark roofs absorb - just as a black asphalt street gets hotter than a light gray concrete one in the summer. Thats nice on a roof in hot climates but can be a negative in cold ones.
For instance, I live on Long Island (NY). My guess is that we use the A/C about 20 days a year on average. Our furnace, however, runs from about the end of Sept. through about Memorial Day. I save far more energy (burn less oil) by absorbing heat in the roof during heating season, than I ever would with reflecting it on the days I need A/C.
That holds true for any building in an area where heat is used more that A/C. If your giant big box store gets to use its roof as a solar collector during a 9 month heating season, that'smre efficient than repelling heat for a 3 month cooling season.
I'm going to assume then ed, that
1) you pipe hot air down from your attic in the winter (which is a fantastic idea) and
2) your roof is not covered in snow in winter (as living in Canada, mine often is).
Answers:
1- Irrelevant - dark roof will still absorb heat and save a little fuel. By the way, I happen to have white shingles because they came with the house and don't need replacement.
2 - Hardly ever covered with snow - mid atlantic climate warmed by the Atlantic ocean. Snow usually does not last that long here because the most common winds are warmed southwest. Sometimes, if the jetstream drops down and stays down, you can have a prolonged cold snap.
Would assume that since you're in Canada, you have little, if any, need for A/C and a much longer heating season than here. If so, a white roof would contribute nothing to lower cooling costs. Snow on the roof would add an insulating layer for you.
Whether you need to save on heating or cooling Stuffing you house, or building, with as much insulation as possible, will work wonders and save far more than a white roof.
Kudos to you ed. You get it. Unfortunately, I think we're in the minority.
Actually, white roofs only reduce energy costs for buildings located in warm climates, most often located below I-40. In fact, calculations conducted on the U.S. Department of Energy's Cool Roof Calculator prove that dark colored roofs can reduce energy costs, consumption and lower carbon emissions for buildings located as far south as Albuquerque, NM. Cities located in cooler climates (like Chicago) are actually increasing their carbon footprint, not reducing it, by mandating white roofs. Unfortunately, they think they're doing the right thing because organizations and associations like the USGBC (LEED) and the Cool Roof Rating Council continue to tout the benefits of reflectivity, and subsequently, seem to get all the media placements. However, their stories fail to mention that reflectivity only contributes to reduced air conditioning usage, which in many locations only takes place in the summer. What about heating usage during the fall, winter and spring? According to the DOE's 2008 Building Energy Data Book, heating accounts for an average of 29% of commercial buildings' end use energy intensity. Cooling only adds up to 6%. So, reducing heating consumption (via dark-colored roofs) would actually be more energy efficient and eco-friendly than trying to reduce air conditioning consumption (via reflective roofs) in many parts of the world. If only we could get some ink on that!
Forget light or dark, what you need is green. They are expensive, but a green roof provides benefits in cold and warm climates with regard to energy consumption by acting as insulation, and just as important, they capture stormwater which would otherwise overflow the sewer system and pollute receiving water bodies. They don't work on steeply pitched roofs, but the green roof is another old technology (think traditional Irsh sod roofs) that needs to be brought back en masse.
Let's stay relevant here zstern.
Not everyone lives in the shire froto. Lol