Thursday, November 15, 2007

Think globally, act locally, save moneyOne of the simplest ways to save energy and money is to have a light colored roof. It the summer a black or dark roof absorbs the suns rays and heats up, a lighter colored roof reflects much of the light. In the winter the darker roof is a much more efficient radiator of solar energy than a lighter one. A few days ago, Eli was up pretty high in a building that overlooked a bunch of row houses in a seedy to improving neighborhood, and he saw that most of the roofs were light, even on the houses that had not been tarted up. So he decided to use Google maps to take a look at the area he lives in. There are very few dark roofs left. Eli suspects that progress has falsified what the EPA says

Over 90% of the roofs in the United States are dark-colored.
Take a look at your neighborhood. The web page continues about dark roofs

These low-reflectance surfaces reach temperatures of 150 to 190°F (66 to 88°C) and contribute to:

  • Increased cooling energy use and higher utility bills;
  • Higher peak electricity demand, raised electricity production costs, and a potentially overburdened power grid;
  • Reduced indoor comfort;
  • Increased air pollution due to the intensification of the "heat island effect"; and
  • Accelerated deterioration of roofing materials, increased roof maintenance costs, and high levels of roofing waste sent to landfills.

In contrast, cool roof systems with high reflectance and emittance stay up to 70°F (39°C) cooler than traditional materials during peak summer weather. Benefits of cool roofs include reduced building heat-gain and saving on summertime air conditioning expenditures. By minimizing energy use, cool roofs do more than save money – they reduce the demand for electric power and resulting air pollution and greenhouse gas emissions.

20 comments:

Boris said...

Wasn't it Ben Franklin who suggested roofs should be dark in the northern colonies and light in the south?

Am I a moron for wanting the plural of roof to be rooves?

Anonymous said...

I don't think you're a moron, Boris, It seems instinctive to me too!
This is just one of the countless examples of solutions that can be easily implemented and, combined together, would have significant potential. Any time that one of these solutions is mentioned, endless crowds jump on it to demonstrate how it would make no difference and, therefore, is too much of a burden. The obvious bad faith of describing that solution outside of a large array of other, concurrently implemented solutions, usually does not prevent the detractors from swaying the masses.

Saturnian

Dan W said...

Maybe part of the discrepancy between the EPA statement and Eli’s observation is one of “what is “light colored”?. The last time I re-roofed (almost a decade ago) the lightest color shingles I found were “tan” nothing even close to “sidewalk grey” was available (is it now?).

Perhaps shingles should come with an albedo rating?

John Mashey said...

Of course, in the long term (100s of years), presumably most roofs will be:
- green, growing
- solar PV, perhaps integrated with tiles
- black, for solar hot water

here's a nice presentation from 2005 on Zero Energy Homes (ZEH) efforts:
www.californiasolarcenter.org/pdfs/forum/2005.2.23-SolarForum_RHammon-ZEH.pdf

Sparrow (in the coal mine) said...

In the winter the darker roof is a much more efficient radiator of solar energy than a lighter one.

Do you have a source on that? The section called "The Winter Penalty" linked to below appears to conflict with your statement.

http://eetd.lbl.gov/HeatIsland/PUBS/PAINTING/

If it doesn't conflict it certainly does claim the net effect in winter is a negative temperature swing and not a positive swing which your statement alludes to.

Anonymous said...

Perhaps shingles should come with an albedo rating?"

hell, the easiest (and cheapest) way to change the albedo of a roof is to paint it -- not with latex, of course, but with asphalt paint. You can actually buy that at the local hardware store and it is usually silver colored -- hence highly reflective.

Hell, paint the lawn and bushes and neighbor's cat while you're at it. Cuts down on mowing and trimming costs too (and pet grooming costs in the latter case).

I bet if everyone did that -- and if the government painted all the parking lots and roads too -- we might see some drop in temperature

I suspect even Anthony Watts would like that, especially if they painted the parking lot at Marysville :)

The only problem I can foresee is that aliens might notice a new star in the sky and come to investigate. WE had better just hope they are like ET and not Dick Cheney.

--T

EliRabett said...

T, in Eli's neighborhood the ladies lynched a guy who poured concrete over his front lawn and painted it green. Of course, that was Brooklyn.

Anonymous said...

My grandfather was a dairy farmer and used to paint his barn with silver asphalt paint on a fairly regular basis.

Don't think he was doing it to be economical, though farmers are usually quite good on that count.


His roof was sheet metal and he was just trying to keep it from rusting away.

There is no reason it would not work with shingles though (not that I can think of, anyway)
--T

Anonymous said...

Hey Rabett, what goes on here.
A single time image that suggests that the EPA consensus of dark roofs is incorrect - can't have that. It only covers 0.000001% of the US mainland anyway, and its not global, so there.
The IPCC(International Committee for Colorless Ceilings) has peer viewed the EPA ceilings. 2000 people who painted, knew painters or heard from someone whose second cousin was a painter can confirm dark roof EPA findings. Paint rings on ceilings confirm dark paint was used. I understand a hockey stick was found on a ceiling.
RC(Restorers and Conjurors) is to publish articles rubbishing light colored roof sightings
JohnS

David B. Benson said...

Trees work wonders, properly planted.

Anonymous said...

I am a Mighty anonymouse.

I was under the impression that rooves were designed to absorb heat for some reason. Perhaps winter heating is a greater good than summer cooling?

Might not a better solution be to cover the roof in PV cells and heat up your water and charge your battery with the insolation?

Anonymous said...

MA here again, battery as in the array that powers your lights and charges your hybrid/electric vehicle.

boreal said...

Hi Eli,
Re: Roofing+GHGW, Yr. getting warm but it berooves you to paddle North for useful solutions to the homeowners energy dilemmas.
Times awastin', all-be-doing "Homespun" elegant energy, when you come for a visit.

Anonymous said...

Scientists have been drawing attention to the ongoing unfolding disaster in irregular plurals for some time, but there are still a few denialists, funded by the EFL lobby. If the current rate of irregularity goes on, English will become unlearnable in a few years. It will have passed the tipping point and our feral young will prowl the streets making the inarticulate noises that will be their only means of communication.

Some denialists say that back in the Medieval Irregular Period (MIP), things were even more... irregular ... Well they were not. Extensive studies of one long lived family, speakers of native Hebredian, show that the MIP was actually more regular than today, and that the following lapse into irregularity was an urban myth.

So roof > rooves, hoof > hooves, and sheep > sheepen, before its too late!

boreal said...

Chimo Amouse,
Chit chatting aboot the placement of fish forks on the Captain's Table sure is fun, but the ship's adrift+sinking fast.
There's free energy aplenty if you can pay attention.
Come for a paddle.
We'll vouchsafe Yr. PFD.

guthrie said...

Lomborg had an article in the Scotsman, the Edinburgh based Scottish take me seriously I want to be a national newspaper newspaper. Stoat reads it sometimes, I have no idea why. I read it because I'm fropm Edinburgh and can remember when it was quite a good paper, not just mediocre.

Anyway, Lomborgs article had very little stupidity in it, and the main thrust seemed to be that painting roofs white was a good idea.

Yes, you read it here first, Lomborg is capable of intelligent thought!

Belette said...

Someone else queried your "In the winter the darker roof is a much more efficient radiator of solar energy than a lighter one". I would expect some minor gain from solar heating a dark roof in winter, though not a lot, as you ought to insulate your loft anyway.

Weasels eat mice but I'm a nice one

flavius collium said...

The sunlight effect is not relevant in the night. And remember it's darker in the winter too...

I've heard from IT emigrants how houses in the silicon valley are lousily insulated and then use heating during the night and AC in the day. (The locals don't think anything is funny with that.)

John Mashey said...

re: Silicon Valley houses

1) Some houses in SV are like that, but the building codes have been improving fast, newer houses are better, and people are starting to build so-called ZEH (Zero Energy Houses).

2) SV has many days of sun, and low humidity, i.e., the air doesn't hold the heat. Hence, during the day, it gets hot, and at night it cools off, so this is less surpoising than you'd think.

3) People are returning to tried-and-true methods for evening out temperature swings, long used in Southwest. For example, our house has thick walls that absorb hear during the day, and re-emit it a night, and use overhang eves to block summer sun. Add being in the hills, and having lots of trees around ... we don't have air conditioning, and don't miss it more than a few night a year, for which turning on a fan suffices. That's a 50-year-old house, but several people in our town are building true ZEHs with modern designs, and we're working LEED standards into the building codes.

void () said...

This is interesting. Many comments seem to not agree with Lomborg. And that would seem to indicate that few would agree with Eli. What's going on here; I'm confused.