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July 30, 2009 12:46 PM

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I don't know how much it costs to replace a roof but how long will it take for the energy savings to make up the cost of replacing it? Another issue is that some people may not see it as cost effective especially if the roof does not need repair or replacement especially in the current economic climate.

4 replies

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Eyebrows McGee (now with more baby!)

July 30, 2009 2:48 PM

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@evilxlilbrat: Yeah, the point with reroofing isn't to tear off perfectly fine roofs -- that creates waste, and \"too much trash\" is an environmental problem too. The point is that if you're RE-roofing, a white roof or a roof with integrated solar panels is generally worth looking into.

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B

July 30, 2009 1:00 PM

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@evilxlilbrat: The point is, if you're already repairing a roof, or for new home constructions, make it white. If your roof is fine, don't bother getting a new one, as the energy savings wouldn't be enough to make it cost effective.

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keepher

July 30, 2009 1:00 PM

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@evilxlilbrat: It doesn't absolutely have to be white. It can be non painted also. We re-roofed this year, no choice. We chose the non painted silver roof since this is not our perm home. Our AC no longer struggles to deal with 100+ temps. The areas that were so hot in the past are gone.

Of course that assumes you also have very good insulation under that metal roof to maximize the sun reflection.

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keepher

July 30, 2009 3:27 PM

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@keepher: One other thing to consider, there is a tax credit since it is considered environmentally friendly.

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July 30, 2009 3:43 PM

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@keepher: Some power companies (not mine, alas) will also provide rebates for such improvements.

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TheBursar

July 30, 2009 12:46 PM

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How much would this add to your heating bills in the winter?

14 replies

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July 30, 2009 5:43 PM

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@TheBursar: I thought the same thing. I live in a state with both extremes, scorching hot summers, and excruciatingly cold winters. Having a white roof would not be conducive to conserving energy in the winter, when my heating bill is much higher than cooling costs in the summer.

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Trai_Dep

July 30, 2009 3:20 PM

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@TheBursar: I've heard rumor that in cold places, millions of people (or cunningly trained penguins, if you hail from Canada) sneak about dusting all uncovered areas with some sort of white powder that is very cold to the touch. Sometimes even several feet of it. Pagan natives sometimes even clump this cold-powder into manlike shapes then ritualistically stab its face with an orange root ripped from the ground so that their children might better do their strange, cold-weather Pagan dances around it.
It seems very inefficient. These very same people that deposited the trillions of tons of this stuff by night the very next morning shovel the stuff off sidewalks and cars, even cursing it. This makes no sense at all.
Cold Area Pagan people are strange, strange people.
In any event, this white cold-powder largely ensures that when it's really cold, roofs are white anyway. So, there's little lost by using white paint.

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Eyebrows McGee (now with more baby!)

July 30, 2009 2:57 PM

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@TheBursar: @floraposte: I live in Central IL -- cold winters, hot summers -- and while my roof SUCKS HEAT all summer when the sun is high in the sky, it's not a notable heat gatherer in the winter, when the sun is low. It's utterly unbearable in the summer. My house is 1.5 stories, so part of the second floor is directly under the roof, and it gets so hot you can hardly breathe when it's hot and the sun is high.

Now, my roof is an east/west exposure; it has no Southern face. I don't particularly notice the southern face of the house is warmer in the winter, either, but because that side is partly shaded by my neighbor's house, that may not be a fair test.

In the winter, there doesn't seem to be any particular heat gain from the roof, though, again, the sun is very low in the sky and my roof has no southern face. My biggest winter heat GAIN (and it's quite minimal) is probably from the red brick western side of my house in the afternoon (which is shaded by trees in summer), my biggest winter heat loss is far and away the windows. I truly don't think painting the roof white would have much effect on my winter heating.

And as someone else pointed out, my roof is frequently covered with snow in the winter ... although snow itself is insulating. :)

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July 30, 2009 3:56 PM

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@Eyebrows McGee (now with more baby!): I think we live in the same house. Actually, yours sounds a little more advantageous in positioning while I suspect I'm better off with trees, but brick, 1.5 stories, central IL. I think it helps that my second floor is white siding, but boy, if I could keep the heat from getting in from above in the first place, that'd be amazing.

The recent threads here have gotten me really interested in reflective roofs/radiant barriers. It takes me a while to research and save for a big spend anyway, and this would give me a good five years to prep for a more heat-resistant roof approach.

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Eyebrows McGee (now with more baby!)

July 30, 2009 4:51 PM

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@floraposte: Central IL Consumerist meet-up! ;)

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littlemisslondon

July 30, 2009 2:36 PM

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@TheBursar: My roof is white by default all winter from snow.

Maybe I should get a white roof and, in the winter, paint all the snow black?

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edosan

July 30, 2009 2:22 PM

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@TheBursar: Have a black roof on hand and switch them out every six months.

Duh.

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July 30, 2009 1:45 PM

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The second law of thermodynamics states that heat flows from areas of high heat to areas of low heat. In the summer, the high heat is outside, on the roof, and in the attic with the cooler (hopefully) area in the house. Heat will flow into the cooler house making it hotter trying to reach equilibrium.

In the winter, the area of higher heat is in the house with the world outside the house being cooler. The flow of heat from a marginally warm roof in the winter will flow away from the house.

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The Porkchop Express

July 30, 2009 3:23 PM

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@Damocles57: I thought the second law of thermodynamics was \"do not talk about thermodynamics\"

Of course you are correct.

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July 30, 2009 5:11 PM

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@The Porkchop Express: Ha! That made me laugh out loud. (But, then again, I teach thermodynamics, so I may not be a representative sample.)

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Julia789

July 30, 2009 1:24 PM

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@TheBursar: We have sort of a similar problem - something that is handy during one season but a problem in the other. Our condo was built during the energy crisis, so they designed the laundry room/utility closet with no vent for the dryer. Back in the late 70's early 80's some builders thought it was good to have clothes dryers blowing back inside the house, helping to heat it in winter.

This is only \"handy\" and energy efficient during the coldest dead of winter in low humidity.

Problem is, the clothes dryer dumps two gallons of water into the air every load of laundry. This equals sticky wet house. I had to buy an \"industrial strength\" dehumidifier to run every time I run the dryer. I also have to run the central air fan every time I run the dryer, to get the heat dispersed throughtout the house or it gets to almost 90º in the laundry room. In the spring and summer I skip the central air fan, and just run the A/C full blast. Sometimes I go to the laundrymat instead but I hate it. I'm not sure what is more expensive; the higher electric bill from running the A/C and dehumidifier, or the couple dollars per load I have to pay at the laundrymat and the waste of hours of my time sitting with really strange people.

We inquired about installing a vent, but due to the location of the laundry/utility room in the \"very middle\" of the condo, not near any exterior walls, it is not feasible the construction guys said. (We offered to pay for it during renovations they were doing on the building.) Dryer vents have to be short and direct, they said. If they are too long or snake through walls they collect lint and catch fire.

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July 30, 2009 1:59 PM

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@Julia789: I wonder if you can do some trick like vent it into a 5 gallon bucket with 1 gallon of water in it. That would catch the lint and condense a lot of the moisture.

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Julia789

July 30, 2009 3:05 PM

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@RevRagnarok:
@econobiker:
@winshape:

I had a \"water lint trap\" from the hardware store, it was a small bucket you keep water in, and it caught some of the lint and condensed a little of the moisture. It had to be emptied and refilled after each load. But only a tiny amount of lint was captured, it got throughout the house. So I started putting old pantyhose legs over the end of the flexible tube vent (whenver one gets a run in it and I can't wear it anymore, I designate it for the dryer vent.) I attach it with a rubber band. It catches lint really well, but I have to change it very often so it does not build up the lint. That way the lint does not get into the air of my house.

The easiest thing for me to do is pretend we don't have a washer and dryer and go to the laundrymat. But it's so tempting to use them instead of the laundrymat, because I'm a busy working mom with lots of laundry. Maybe I should look into a wash and fold service.

Yes, the builder of our condos was an idiot to put the non-venting dryer set up inside a utility closet of a condo. We have had lots of other problems too, 10 years of condo drama with leaks and such. They are doing renovations now. When the renovations are done, we hope to sell when the market picks up and get a \"normal\" house with a dryer that vents outdoors, and without the other problems we've had. Heck, I might even just rent a house. At least that way if there is a major problem, I can move when the lease is up!

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Trai_Dep

July 30, 2009 3:29 PM

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@Julia789: It sounds more that an incompetent, lazy contractor tried blaming \"energy efficiency\" for not doing his job properly.

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Julia789

July 30, 2009 4:02 PM

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@Trai_Dep: That's probably the case. They did a sloppy job on other parts of the building, so it fits the pattern.

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July 30, 2009 1:45 PM

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@Julia789: Maybe you could use one of those interior lint traps to help capture some of the water...

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winshape

July 30, 2009 1:44 PM

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@Julia789: So allowing the dryer to vent into the house magically makes the flammable lint disappear? Sounds like whoever designed these condos didn't know what he was doing.

I'm sure that there is some code against that somewhere.

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W10002

July 30, 2009 1:21 PM

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@TheBursar: Living in Southern California, I don't think heating would be a problem. This solution is probably best for warmer areas [as humphrmi said].

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July 30, 2009 12:47 PM

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@TheBursar: Maybe it would be more beneficial to individuals living in warmer climates and not somewhere that has 4 seasons or shorter summer months?

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July 30, 2009 12:46 PM

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Wouldn't you have a near-equal increase in heating costs during winter though? The sun is a big contributor to warming your house before the heater has kicked in.

6 replies

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ztoop

July 30, 2009 2:40 PM

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@punkrawka: I think the main reason heating your home is less of a problem is because most people use gas to heat their homes. This is much more efficient (amount of C02 per therm) than using electricity to cool your home (or heat your home for some temperature change). In the far North most people tend to keep the ac off except for a few days a year, and so there is very little benefit from the white roof.

Also, the white roof reflects sunlight back out of the earth, and so has a net cooling effect on the whole earth. If every home had a white roof, this can have an impact on the total amount of heat for the whole earth.

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Trai_Dep

July 30, 2009 3:38 PM

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@ztoop: Which, by the way, is a plus. It's Global Warming, not Global Cooling. Don't worry, our shrinking ice-caps will more than compensate for white roofs (although, every bit helps).

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Kimaroo - 100% Pure Natural Kitteh

July 30, 2009 3:23 PM

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@ztoop: Did you just solve global warming?

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Julia789

July 30, 2009 1:27 PM

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@punkrawka: Probably depends on what area of the country you live in, and how cold your winters are. Big difference between New York and Arizona, for example.

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July 30, 2009 12:50 PM

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@punkrawka: I guess I should get a RTFA for that... it says this only becomes a net loss in far-northern areas like Detroit/Minnesota.

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keepher

July 30, 2009 1:02 PM

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@punkrawka: That's about like the suggestion we live without central air in the deep south. It will depend on where you live and how much sun you get.

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Frapp

July 30, 2009 12:52 PM

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If it's merely a question of reflectivity, then why couldn't one just have a white covering for the roof during the summer months, then use the existing dark roof for the cold months? That is of course, if a white roof would be bad during the cold months.

I'm sure something like a tarp would just look hideous (and probably muck with property values) However there's gotta be a way to make something like this cost effective AND easy to install as well as remove & store.

3 replies

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Applyin'Sunscreen_GitEmSteveDave

July 30, 2009 1:24 PM

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@Frapp: It must also breathe, or it would cause horrible mold and moss problems.

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July 30, 2009 1:55 PM

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@Applyin'Sunscreen_GitEmSteveDave: No reason why it couldn't have perforations, though. And that would probably reduce the chance of damage during high winds.

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July 30, 2009 1:21 PM

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@Frapp: IIRC there's some roofs our there that are both black and white. They're installed such that during the summer the sun primarily hits the white part and during the winter the sun, which is at a different angle now, primarily hits the black parts.

I don't know if they're actually commercially available or if they were just experiments.

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humphrmi

July 30, 2009 12:55 PM

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@TheBursar: I guess it would depend on how your house / apartment is built with respect to the roof. In my case, I have a roof then immediately under the roof structure is a walk-up attic, followed by a tri-split level below that. If the roof absorbs heat, it will pass that heat down to the attic at best (remember heat rises).

I suppose if your living space is immediately under a roof, you would benefit from having the roof absorb heat, thus a black (or dark) roof. Otherwise, I can't think of any heating benefit.

2 replies

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July 30, 2009 1:13 PM

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@humphrmi: That is a good analysis, but you also need to consider the overall energy flows of the house. Even though the heat gain by the roof will likely only pass into the attic space, that still increases the overall thermal mass of the interior, which would slow heat loss from the lower levels of the house into the attic.

Of course, if you have leaky doors/windows/walls, this point is moot. The whole insulation industry really needs better PR - insulation ain't sexy, but it is relatively cheap, and has one of the best energy payback times.

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July 30, 2009 1:22 PM

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@mechteach: Unless you've got truly fabulous insulation, there's likely to be temperature bleed from the attic/under-roof space into the house, too. Ultimately, I suspect, as was discussed on a previous thread, that in most climates requiring AC in the summer the roof-borne heat gain in winter isn't hugely significant, but I'd be really interested in getting some kind of individual assessment--it's bound to make a difference how your roof slants and faces, what other surfaces get presented to the sun, what kind of tree cover you've got, etc.

I'm with you on the insulation, though. Just weather-stripping my doorframes was phenomenally helpful, and I'm looking into getting a genuine access hatch cut into the attic so I can revamp the insulation properly up there (right now it can only have blown in since there's no human access).

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catastrophegirl chooses not to fly

July 30, 2009 4:45 PM

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@floraposte: my attic has pull down steps and above it, the previous owners had a box with doors that pull over and down to close over it, keeps the cool house air out of the attic.

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July 30, 2009 6:24 PM

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@catastrophegirl - bingo burn-out: I've looked at those (I actually have to get my hatch widened if I want to do any work in the attic, since it's too small to fit humans at 12\"x14\"), but the 1.5 story means that there's a fair amount of 2nd story that's directly under the roof with no intervening attic space. That's where the heat piles in. So an improved roof barrier is of great interest to me.

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Saboth

July 30, 2009 12:58 PM

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They should make color changing shingles that change to white when it is 70 degrees outside, and dark when it is 50 degrees out.

2 replies

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Julia789

July 30, 2009 1:28 PM

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@Saboth: You should invent them. They already make children's toys that change color in hot or cold temperature. Why not roof shingles?

Or just a big retractable white roof shade for summer LOL.

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Eyebrows McGee (now with more baby!)

July 30, 2009 3:00 PM

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@Julia789: You know what's totally making a comeback where I am? Awnings. Every house in my neighborhood has the clips and bars for summer window-shading awnings from the pre-central-air days, but only the old people still used them ... until recently when a combination of environmental awareness and high energy costs has everyone asking the old people, \"Now where do you get those awnings from?\"

The awning guys could totally branch out into roof shades!

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Julia789

July 30, 2009 3:57 PM

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@Eyebrows McGee (now with more baby!): Like those \"Sunsetter Retractable Awnings\" commercials, which show happy old folk drinking lemonade and clicking the remote control for the awning - LOL. They just need a giant one for the roof.

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Applyin'Sunscreen_GitEmSteveDave

July 30, 2009 1:01 PM

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Doesn't Black Body Radiation tell us that the color black radiates the most energy away from itself? As for painting, I would recommend careful selective painting, drawn from past Consumerist posts:
[consumerist.com]

> [consumerist.com]

2 replies

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Skaperen

July 30, 2009 5:48 PM

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@Applyin'Sunscreen_GitEmSteveDave: Only a portion of the heat that is acquired is re-radiated. Making the roof white in the day then black at night would do the best. Reflection works best when the sun is beating down on it. Then at night, radiate back out the heat that was acquired (a fraction leaking through the white earlier, and the convection heating from the air).

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July 30, 2009 1:26 PM

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@Applyin'Sunscreen_GitEmSteveDave: Right. And that's bad. You don't want a roof that radiates, because it's absorbing the heat. You want a roof that reflects.

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I Love New Jersey

July 30, 2009 1:01 PM

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My gut says that the capital investment will probably take a long time to get return on in utility savings. Which makes me wonder would it be better to replace the roof with solar panels, as you can actually generate some power from them?

4 replies

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Applyin'Sunscreen_GitEmSteveDave

July 30, 2009 1:14 PM

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@I Love New Jersey: You would also extend the life of your roof, AND cool your house as the panel absorb both the elements and much of the suns energy, stopping both from touching your roof. Your attic not heating up will save you a lot of cooling cost. Also most panels have a 30 year warranty as well.

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Alereon

July 30, 2009 1:27 PM

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@Applyin'Sunscreen_GitEmSteveDave: Solar panels make your house hotter. The panel itself converts only a small portion of the light that strikes it into electricity (20% at the very best), the vast majority is turned into waste heat (this is how solar water heaters work). Since solar panels are very dark black, this is a significant heat increase over sunlight landing on your roof.

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Applyin'Sunscreen_GitEmSteveDave

July 30, 2009 2:39 PM

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@Alereon: Except that the best insulator is located between the panels and your roof, air. It is, in all reality, shading your roof.

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Alereon

July 31, 2009 12:19 AM

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@Applyin'Sunscreen_GitEmSteveDave: A typical residential solar panel installation is flush with the roof, leaving at best a couple inches of air gap between the panels and your roof. Some installations do mount the panels on brackets off of the roof surface, if the roof is at a poor angle to capture the sun for example, but the added heat from the panels is very much a real problem that has to be worked around if you don't want it to impact your cooling bill.

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July 30, 2009 1:26 PM

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@Applyin'Sunscreen_GitEmSteveDave:And cost considerably more than a new roof, at least around these parts.

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July 30, 2009 1:07 PM

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@I Love New Jersey: I think the point is not for the population of the U.S. to run out, en masse, and have new roofs put up for thousands of dollars in an effort to save $25 a month, but for a gradual transition as individual homeowner roofs need to be replaced.

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July 30, 2009 1:24 PM

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Eye sore.

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zegolf

July 30, 2009 1:25 PM

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My HOA would have a conniption if I tried this.

It does seem like it makes sense though. It's basic middle-school Science. Darker colors absorb more heat, ergo a darker roof would make a house hotter. Sort of makes you wonder why we've been installing dark shingles for years and years.

4 replies

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Skaperen

July 30, 2009 5:50 PM

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@zegolf: Then don't live in an HOA governed development. Those places are nasty, with horrible people running them.

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The-Lone-Gunman

July 31, 2009 9:28 PM

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@Skaperen: Easier said than done in many parts of the country now.

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The-Lone-Gunman

July 30, 2009 4:57 PM

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@zegolf: My HOA would have a conniption if I tried this.

I was wondering about this; so many HOAs are power-mad when it comes to the slightest thing that they consider 'different' from all the other units in the neighborhood. How many of them would force the homeowner to revert the roof back to the original?

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kaceetheconsumer

July 30, 2009 4:57 PM

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@zegolf: Yeah, most HOAs are horrible about most energy-saving stuff unless required by law (ie in Nevada now your HOA can't block you from installing things like solar screens, solar hot water systems, etc).

It's why we'll never go HOA again.

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July 30, 2009 1:27 PM

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this actually does work very well. my wife's great grandmother has a porch that has a metal roof. in the summer time the porch would be almost unbearable. we painted the roof white and installed some white styrofoam in between the roof supports. now the porch is nice and cool.

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ncpeters

July 30, 2009 1:44 PM

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Would this apply if you have shingles? I've never seen white shingles but here in Iowa all homes have shingles. Iowa probably isn't a place that would benefit from white roofs anyways, because the increased heating costs would cancel out the air conditioning savings.

3 replies

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Skaperen

July 30, 2009 5:51 PM

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@ncpeters: Once you have snow on the roof, what's the difference between that and white shingles.

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July 30, 2009 6:27 PM

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@Skaperen: I suspect not much--as long as you're sufficiently well-insulated that the snow stays on the roof even in sun. A lot of houses round my parts aren't.

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July 30, 2009 2:06 PM

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@ncpeters: Yup, it applies to shingles as well; lighter-colored shingle roofs will heat up less (now I'm not so annoyed about pale gray vs. the dark gray I wanted) and reflect more, and you can get reflective shingles.

Judging by what the article says, Iowa's in the zone that could still benefit, especially if you're in town. It sounds like the winter factor is pretty negligible, actually, and that the real issue is how much electricity you use in summer to cool yourself down. If you're in a region where you don't run the A/C anyway, it's not going to help you much, but if you've got hot enough summers that you power-cool through it, it doesn't matter that the winters are cold, you'll still benefit. (That's what it sounds like, anyway.)

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bingo-ok

July 30, 2009 1:51 PM

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Commenters keep referring to the cost of roofing and earning it back, but roofs do not last forever. They get replaced all the time either from age or from weather-damage. You don't have to make back the whole cost of re-roofing. You were going to spend that anyway. You only have to make back the 15% premium the article mentions white roofs cost over dark roofs. And if you're saving 20% on energy costs, I don't see how it could take very long to make it back.

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July 30, 2009 1:54 PM

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As I previously commented, where I grew up on the NJ shore 30 years ago white/grey (and some other colors green/red/blue) roofs were common. This probably ended due to home fashion and the extra expense to purchase lighter colored roofing materials versus materials which tended toward the darker colors of petroleum products.

White roofing HAS to be able to help in some areas. When flying into Dallas TX in the summer, you see the desert like environment and then thousands of dark roofed homes just baking away in the sun. Surely white or grey roofing would help reduce cooling costs incrementally much like CFL bulbs help reduce engergy use.

The only other issue that people have brought up about white roofing in southern climes is green mold that is not killed by cold temps during the winter...

2 replies

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July 30, 2009 8:46 PM

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@econobiker: \"desert like environment\": You have to be way farther west and south of Dallas before you hit a desert. Simply hot does not a desert make. It's not Jersey, but it's not a desert, either.

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Applyin'Sunscreen_GitEmSteveDave

July 30, 2009 3:17 PM

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@econobiker: True. After how long would the dirt/grime turn that white roof dark?

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PSUSkier

July 30, 2009 1:55 PM

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I know this may not work for all instances, but if you have a decent amount of insulation between your crawlspace/attic then an easier and cheaper solution would be to install a high efficiency attic fan.

2 replies

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clickertrainer

July 30, 2009 4:29 PM

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@PSUSkier: I have a whole house fan and it's amazing. Got a rebate from the power company too.

@eyebrows_etc The one in my current house was installed by a pro and is almost silent. The one in my old house was installed by my now ex mechanical engineer husband and sounded like a jet engine. Trust the pro installer, not the MSME.

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Eyebrows McGee (now with more baby!)

July 30, 2009 3:03 PM

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@PSUSkier: I have one of those, and it IS teh awesomeburgers. It'd be even better if my house didn't suck up so much heat in the first place.

(Also, ours is crazy loud. But a newer model would fix that, I'm sure.)

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July 30, 2009 2:00 PM

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Neither the article referred to nor the intro by Consumerist is advocating tearing out perfectly good roofs just to install white reflective roofs. The message is that if you are going to reroof or are building new and need to roof anyway, white might be something to consider.

There are variables beyond the color of your roof in your area: amount of sun that actually hits your roof (trees or other shade), slope of the property, number and types of windows and curtains, comfort levels, amount of insulation in your building envelope, natural ventilation, cost of utilities in your area, varying amounts of local, state or federal \"encouragement\", etc.

As with everything, it is prudent to look at your specific circumstances, do some research and crunch some numbers.

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sp00nix

July 30, 2009 2:07 PM

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My buddies shop remains pretty cool. Its a bog box with no AC, but during our heat waves tends to be cooler then my house. I happen to live 2 doors down and the other day i noticed the roof had a silver finnish on it. now i know his secret!

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idx

July 30, 2009 2:10 PM

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Check out www.tempcoat.com

It's a liquid ceramic insulation that you apply on top of roofs that will cut your energy bill in both summer and winter about 20-25 percent.

I put it in my attic since I didn't want a white roof and it's saved me about 15% on my cooling costs this summer. Plus, they're a local company. Big up South Eastern Louisiana.

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July 30, 2009 2:11 PM

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@florapost: Probably a good idea in any case. You should have access to the attic spaces to check for rotting in your roof joists and plywood sheeting. If your roof has a small leak, over time the wood will rot out and it's hideously expensise to replace that on top of paying for the shingles.

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humphrmi

July 30, 2009 2:19 PM

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@mechteach: Good point about thermal mass, I hadn't thought about that. I guess that's why most roofs in my area (Chicago area: hot in the summer, cold in the winter) are grey - some absorption in the winter, and some deflection in the summer ;-)

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morlo

July 30, 2009 2:42 PM

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Doesn't matter what color your roof is if it's covered in solar panels.

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jokono

July 30, 2009 3:27 PM

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@morlo: True in more ways than one. Not only do you get the benefit of solar power, but the silicon in the panels reflects infrared radiation away from your home -- keeping you cooler than even a white roof would. I am very seriously considering solar panels for the back part of my pitched roof.

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July 30, 2009 3:22 PM

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Calculate your potential savings here:

[www.roofcalc.com]

Even in more northerly climes where heating-degree-days far outnumber cooling-degree-days, more-reflective roofs still provide advantages. Due the the low angle of the sun during winter and shorter days, 6 months of \"good\" wintertime heat gain amounts to less than less than 3 months of \"bad\" summertime heat gain.

My husband used to rent the house we now own, and he said he couldn't get the former owner to chose light-colored shingles when it was re-roofed about 10 years ago. According to the above calculator, that would have made a difference of about $150/year for us. Not a ton of money, but if you're reroofing anyhow, it's better than a stick in the eye.

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bobpence

July 30, 2009 4:42 PM

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If you're replacing a roof, it certainly makes sense to calculate the payoff period for improvements such as this or having solar panels installed. Nothing but the economic costs are likely to matter, and the costs and benefits will accrue to individual households. We could turn every road, rood, and parking lot white and still cover less than 2% of the surface area of our land.

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catastrophegirl chooses not to fly

July 30, 2009 4:52 PM

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i'm going to have to get a couple of thermometers. the people i bought the house from replaced half the roof for me [i only asked for it to be patched where it leaked so i'm not complaining at all]

[www.flickr.com]

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JiminyChristmas

July 30, 2009 5:02 PM

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The difference in reflectivity between a light-colored asphalt shingle and a dark-colored one is actually not that big. They both still have asphalt substrates so they both still absorb a lot of heat relative to other types of roofing.

If you want a cool roof for your house a metal roof is a good option. Its reflectivity is 2x-3x greater than a white asphalt shingle. It's also likely to be more durable and architecturally appropriate than other solutions, like white coatings. Metal roofing typically comes in panels, but there are metal shingles as well. On the downside, a metal roof can also cost 2x-3x more than a shingle job.

Another option is to use a reflective roofing underlayment. These are usually either a plastic sheet with a metallic coating or a flexible reinforced metal foil and are surprisingly effective at blocking radiant heat gains. The only tricky thing with these is that most of them are not vapor permeable and can create condensation problems, depending upon your climate and where the underlayment is in the roof assembly.

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July 30, 2009 5:46 PM

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Good luck trying to get your HOA to sign off on having the only white roof in a neighborhood of black roofs.

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Skaperen

July 30, 2009 5:56 PM

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@halcyondays: People like you that sign away all their rights are as much of a problem as the power hungry people that run HOAs. So ... collectively ... you guys are why we have so much electric demand. Now we have to make this a law to get it to work. No wonder people don't just voluntarily do the right things.

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July 30, 2009 5:50 PM

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This just in:

Save on heating costs by installing a black roof!

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mrearly2

July 30, 2009 6:15 PM

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When the attic has a proper amount of insulation, the roofing color won't make much of (if any) a difference to the temp in the house. If a different roof color has an impact on your household energy usage, then you've got a poorly built and/or poorly insulated house.

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JiminyChristmas

July 30, 2009 9:11 PM

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@mrearly2: Most houses could be better insulated, but that's not entirely accurate.

On a clear summer day a dark-colored roof can absorb enough heat to raise the roof surface temperature 50 or more degrees higher than the ambient air temperature. Heat transfer is partly affected by the temperature differential you are trying to maintain. If your desired indoor air temperature is 70 degrees and it's 90 degrees outside you could have a difference of 70 degrees from the outside surface of your dark roof to the inside. Even if you had modern roof insulation of R-38 or greater you would still get a substantial amount of heat conducted or radiated through the roof.

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krista

July 30, 2009 10:13 PM

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A radiant barrier installed in the attic will do pretty much the same thing at a much lower cost.

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